OSCL-LXR linux-6.0.1/​net/​netlink/​af_netlink.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * NETLINK      Kernel-user communication protocol.
  *
  *      Authors:    Alan Cox <alan@lxorguk.ukuu.org.uk>
  *              Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
  *              Patrick McHardy <kaber@trash.net>
  *
  * Tue Jun 26 14:36:48 MEST 2001 Herbert "herp" Rosmanith
  *                               added netlink_proto_exit
  * Tue Jan 22 18:32:44 BRST 2002 Arnaldo C. de Melo <acme@conectiva.com.br>
  *               use nlk_sk, as sk->protinfo is on a diet 8)
  * Fri Jul 22 19:51:12 MEST 2005 Harald Welte <laforge@gnumonks.org>
  *               - inc module use count of module that owns
  *                 the kernel socket in case userspace opens
  *                 socket of same protocol
  *               - remove all module support, since netlink is
  *                 mandatory if CONFIG_NET=y these days
  */
 
 #include <linux/module.h>
 
 #include <linux/bpf.h>
 #include <linux/capability.h>
 #include <linux/kernel.h>
 #include <linux/filter.h>
 #include <linux/init.h>
 #include <linux/signal.h>
 #include <linux/sched.h>
 #include <linux/errno.h>
 #include <linux/string.h>
 #include <linux/stat.h>
 #include <linux/socket.h>
 #include <linux/un.h>
 #include <linux/fcntl.h>
 #include <linux/termios.h>
 #include <linux/sockios.h>
 #include <linux/net.h>
 #include <linux/fs.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 #include <linux/skbuff.h>
 #include <linux/netdevice.h>
 #include <linux/rtnetlink.h>
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
 #include <linux/notifier.h>
 #include <linux/security.h>
 #include <linux/jhash.h>
 #include <linux/jiffies.h>
 #include <linux/random.h>
 #include <linux/bitops.h>
 #include <linux/mm.h>
 #include <linux/types.h>
 #include <linux/audit.h>
 #include <linux/mutex.h>
 #include <linux/vmalloc.h>
 #include <linux/if_arp.h>
 #include <linux/rhashtable.h>
 #include <asm/cacheflush.h>
 #include <linux/hash.h>
 #include <linux/genetlink.h>
 #include <linux/net_namespace.h>
 #include <linux/nospec.h>
 #include <linux/btf_ids.h>
 
 #include <net/net_namespace.h>
 #include <net/netns/generic.h>
 #include <net/sock.h>
 #include <net/scm.h>
 #include <net/netlink.h>
 #define CREATE_TRACE_POINTS
 #include <trace/events/netlink.h>
 
 #include "af_netlink.h"
 
 struct listeners {
     struct rcu_head     rcu;
     unsigned long       masks[];
 };
 
 /* state bits */
 #define NETLINK_S_CONGESTED     0x0
 
 static inline int netlink_is_kernel(struct sock *sk)
 {
     return nlk_sk(sk)->flags & NETLINK_F_KERNEL_SOCKET;
 }
 
 struct netlink_table *nl_table __read_mostly;
 EXPORT_SYMBOL_GPL(nl_table);
 
 static DECLARE_WAIT_QUEUE_HEAD(nl_table_wait);
 
 static struct lock_class_key nlk_cb_mutex_keys[MAX_LINKS];
 
 static const char *const nlk_cb_mutex_key_strings[MAX_LINKS + 1] = {
     "nlk_cb_mutex-ROUTE",
     "nlk_cb_mutex-1",
     "nlk_cb_mutex-USERSOCK",
     "nlk_cb_mutex-FIREWALL",
     "nlk_cb_mutex-SOCK_DIAG",
     "nlk_cb_mutex-NFLOG",
     "nlk_cb_mutex-XFRM",
     "nlk_cb_mutex-SELINUX",
     "nlk_cb_mutex-ISCSI",
     "nlk_cb_mutex-AUDIT",
     "nlk_cb_mutex-FIB_LOOKUP",
     "nlk_cb_mutex-CONNECTOR",
     "nlk_cb_mutex-NETFILTER",
     "nlk_cb_mutex-IP6_FW",
     "nlk_cb_mutex-DNRTMSG",
     "nlk_cb_mutex-KOBJECT_UEVENT",
     "nlk_cb_mutex-GENERIC",
     "nlk_cb_mutex-17",
     "nlk_cb_mutex-SCSITRANSPORT",
     "nlk_cb_mutex-ECRYPTFS",
     "nlk_cb_mutex-RDMA",
     "nlk_cb_mutex-CRYPTO",
     "nlk_cb_mutex-SMC",
     "nlk_cb_mutex-23",
     "nlk_cb_mutex-24",
     "nlk_cb_mutex-25",
     "nlk_cb_mutex-26",
     "nlk_cb_mutex-27",
     "nlk_cb_mutex-28",
     "nlk_cb_mutex-29",
     "nlk_cb_mutex-30",
     "nlk_cb_mutex-31",
     "nlk_cb_mutex-MAX_LINKS"
 };
 
 static int netlink_dump(struct sock *sk);
 
 /* nl_table locking explained:
  * Lookup and traversal are protected with an RCU read-side lock. Insertion
  * and removal are protected with per bucket lock while using RCU list
  * modification primitives and may run in parallel to RCU protected lookups.
  * Destruction of the Netlink socket may only occur *after* nl_table_lock has
  * been acquired * either during or after the socket has been removed from
  * the list and after an RCU grace period.
  */
 DEFINE_RWLOCK(nl_table_lock);
 EXPORT_SYMBOL_GPL(nl_table_lock);
 static atomic_t nl_table_users = ATOMIC_INIT(0);
 
 #define nl_deref_protected(X) rcu_dereference_protected(X, lockdep_is_held(&nl_table_lock));
 
 static BLOCKING_NOTIFIER_HEAD(netlink_chain);
 
 
 static const struct rhashtable_params netlink_rhashtable_params;
 
 void do_trace_netlink_extack(const char *msg)
 {
     trace_netlink_extack(msg);
 }
 EXPORT_SYMBOL(do_trace_netlink_extack);
 
 static inline u32 netlink_group_mask(u32 group)
 {
     if (group > 32)
         return 0;
     return group ? 1 << (group - 1) : 0;
 }
 
 static struct sk_buff *netlink_to_full_skb(const struct sk_buff *skb,
                        gfp_t gfp_mask)
 {
     unsigned int len = skb_end_offset(skb);
     struct sk_buff *new;
 
     new = alloc_skb(len, gfp_mask);
     if (new == NULL)
         return NULL;
 
     NETLINK_CB(new).portid = NETLINK_CB(skb).portid;
     NETLINK_CB(new).dst_group = NETLINK_CB(skb).dst_group;
     NETLINK_CB(new).creds = NETLINK_CB(skb).creds;
 
     skb_put_data(new, skb->data, len);
     return new;
 }
 
 static unsigned int netlink_tap_net_id;
 
 struct netlink_tap_net {
     struct list_head netlink_tap_all;
     struct mutex netlink_tap_lock;
 };
 
 int netlink_add_tap(struct netlink_tap *nt)
 {
     struct net *net = dev_net(nt->dev);
     struct netlink_tap_net *nn = net_generic(net, netlink_tap_net_id);
 
     if (unlikely(nt->dev->type != ARPHRD_NETLINK))
         return -EINVAL;
 
     mutex_lock(&nn->netlink_tap_lock);
     list_add_rcu(&nt->list, &nn->netlink_tap_all);
     mutex_unlock(&nn->netlink_tap_lock);
 
     __module_get(nt->module);
 
     return 0;
 }
 EXPORT_SYMBOL_GPL(netlink_add_tap);
 
 static int __netlink_remove_tap(struct netlink_tap *nt)
 {
     struct net *net = dev_net(nt->dev);
     struct netlink_tap_net *nn = net_generic(net, netlink_tap_net_id);
     bool found = false;
     struct netlink_tap *tmp;
 
     mutex_lock(&nn->netlink_tap_lock);
 
     list_for_each_entry(tmp, &nn->netlink_tap_all, list) {
         if (nt == tmp) {
             list_del_rcu(&nt->list);
             found = true;
             goto out;
         }
     }
 
     pr_warn("__netlink_remove_tap: %p not found\n", nt);
 out:
     mutex_unlock(&nn->netlink_tap_lock);
 
     if (found)
         module_put(nt->module);
 
     return found ? 0 : -ENODEV;
 }
 
 int netlink_remove_tap(struct netlink_tap *nt)
 {
     int ret;
 
     ret = __netlink_remove_tap(nt);
     synchronize_net();
 
     return ret;
 }
 EXPORT_SYMBOL_GPL(netlink_remove_tap);
 
 static __net_init int netlink_tap_init_net(struct net *net)
 {
     struct netlink_tap_net *nn = net_generic(net, netlink_tap_net_id);
 
     INIT_LIST_HEAD(&nn->netlink_tap_all);
     mutex_init(&nn->netlink_tap_lock);
     return 0;
 }
 
 static struct pernet_operations netlink_tap_net_ops = {
     .init = netlink_tap_init_net,
     .id   = &netlink_tap_net_id,
     .size = sizeof(struct netlink_tap_net),
 };
 
 static bool netlink_filter_tap(const struct sk_buff *skb)
 {
     struct sock *sk = skb->sk;
 
     /* We take the more conservative approach and
      * whitelist socket protocols that may pass.
      */
     switch (sk->sk_protocol) {
     case NETLINK_ROUTE:
     case NETLINK_USERSOCK:
     case NETLINK_SOCK_DIAG:
     case NETLINK_NFLOG:
     case NETLINK_XFRM:
     case NETLINK_FIB_LOOKUP:
     case NETLINK_NETFILTER:
     case NETLINK_GENERIC:
         return true;
     }
 
     return false;
 }
 
 static int __netlink_deliver_tap_skb(struct sk_buff *skb,
                      struct net_device *dev)
 {
     struct sk_buff *nskb;
     struct sock *sk = skb->sk;
     int ret = -ENOMEM;
 
     if (!net_eq(dev_net(dev), sock_net(sk)))
         return 0;
 
     dev_hold(dev);
 
     if (is_vmalloc_addr(skb->head))
         nskb = netlink_to_full_skb(skb, GFP_ATOMIC);
     else
         nskb = skb_clone(skb, GFP_ATOMIC);
     if (nskb) {
         nskb->dev = dev;
         nskb->protocol = htons((u16) sk->sk_protocol);
         nskb->pkt_type = netlink_is_kernel(sk) ?
                  PACKET_KERNEL : PACKET_USER;
         skb_reset_network_header(nskb);
         ret = dev_queue_xmit(nskb);
         if (unlikely(ret > 0))
             ret = net_xmit_errno(ret);
     }
 
     dev_put(dev);
     return ret;
 }
 
 static void __netlink_deliver_tap(struct sk_buff *skb, struct netlink_tap_net *nn)
 {
     int ret;
     struct netlink_tap *tmp;
 
     if (!netlink_filter_tap(skb))
         return;
 
     list_for_each_entry_rcu(tmp, &nn->netlink_tap_all, list) {
         ret = __netlink_deliver_tap_skb(skb, tmp->dev);
         if (unlikely(ret))
             break;
     }
 }
 
 static void netlink_deliver_tap(struct net *net, struct sk_buff *skb)
 {
     struct netlink_tap_net *nn = net_generic(net, netlink_tap_net_id);
 
     rcu_read_lock();
 
     if (unlikely(!list_empty(&nn->netlink_tap_all)))
         __netlink_deliver_tap(skb, nn);
 
     rcu_read_unlock();
 }
 
 static void netlink_deliver_tap_kernel(struct sock *dst, struct sock *src,
                        struct sk_buff *skb)
 {
     if (!(netlink_is_kernel(dst) && netlink_is_kernel(src)))
         netlink_deliver_tap(sock_net(dst), skb);
 }
 
 static void netlink_overrun(struct sock *sk)
 {
     struct netlink_sock *nlk = nlk_sk(sk);
 
     if (!(nlk->flags & NETLINK_F_RECV_NO_ENOBUFS)) {
         if (!test_and_set_bit(NETLINK_S_CONGESTED,
                       &nlk_sk(sk)->state)) {
             sk->sk_err = ENOBUFS;
             sk_error_report(sk);
         }
     }
     atomic_inc(&sk->sk_drops);
 }
 
 static void netlink_rcv_wake(struct sock *sk)
 {
     struct netlink_sock *nlk = nlk_sk(sk);
 
     if (skb_queue_empty_lockless(&sk->sk_receive_queue))
         clear_bit(NETLINK_S_CONGESTED, &nlk->state);
     if (!test_bit(NETLINK_S_CONGESTED, &nlk->state))
         wake_up_interruptible(&nlk->wait);
 }
 
 static void netlink_skb_destructor(struct sk_buff *skb)
 {
     if (is_vmalloc_addr(skb->head)) {
         if (!skb->cloned ||
             !atomic_dec_return(&(skb_shinfo(skb)->dataref)))
             vfree(skb->head);
 
         skb->head = NULL;
     }
     if (skb->sk != NULL)
         sock_rfree(skb);
 }
 
 static void netlink_skb_set_owner_r(struct sk_buff *skb, struct sock *sk)
 {
     WARN_ON(skb->sk != NULL);
     skb->sk = sk;
     skb->destructor = netlink_skb_destructor;
     atomic_add(skb->truesize, &sk->sk_rmem_alloc);
     sk_mem_charge(sk, skb->truesize);
 }
 
 static void netlink_sock_destruct(struct sock *sk)
 {
     struct netlink_sock *nlk = nlk_sk(sk);
 
     if (nlk->cb_running) {
         if (nlk->cb.done)
             nlk->cb.done(&nlk->cb);
         module_put(nlk->cb.module);
         kfree_skb(nlk->cb.skb);
     }
 
     skb_queue_purge(&sk->sk_receive_queue);
 
     if (!sock_flag(sk, SOCK_DEAD)) {
         printk(KERN_ERR "Freeing alive netlink socket %p\n", sk);
         return;
     }
 
     WARN_ON(atomic_read(&sk->sk_rmem_alloc));
     WARN_ON(refcount_read(&sk->sk_wmem_alloc));
     WARN_ON(nlk_sk(sk)->groups);
 }
 
 static void netlink_sock_destruct_work(struct work_struct *work)
 {
     struct netlink_sock *nlk = container_of(work, struct netlink_sock,
                         work);
 
     sk_free(&nlk->sk);
 }
 
 /* This lock without WQ_FLAG_EXCLUSIVE is good on UP and it is _very_ bad on
  * SMP. Look, when several writers sleep and reader wakes them up, all but one
  * immediately hit write lock and grab all the cpus. Exclusive sleep solves
  * this, _but_ remember, it adds useless work on UP machines.
  */
 
 void netlink_table_grab(void)
     __acquires(nl_table_lock)
 {
     might_sleep();
 
     write_lock_irq(&nl_table_lock);
 
     if (atomic_read(&nl_table_users)) {
         DECLARE_WAITQUEUE(wait, current);
 
         add_wait_queue_exclusive(&nl_table_wait, &wait);
         for (;;) {
             set_current_state(TASK_UNINTERRUPTIBLE);
             if (atomic_read(&nl_table_users) == 0)
                 break;
             write_unlock_irq(&nl_table_lock);
             schedule();
             write_lock_irq(&nl_table_lock);
         }
 
         __set_current_state(TASK_RUNNING);
         remove_wait_queue(&nl_table_wait, &wait);
     }
 }
 
 void netlink_table_ungrab(void)
     __releases(nl_table_lock)
 {
     write_unlock_irq(&nl_table_lock);
     wake_up(&nl_table_wait);
 }
 
 static inline void
 netlink_lock_table(void)
 {
     unsigned long flags;
 
     /* read_lock() synchronizes us to netlink_table_grab */
 
     read_lock_irqsave(&nl_table_lock, flags);
     atomic_inc(&nl_table_users);
     read_unlock_irqrestore(&nl_table_lock, flags);
 }
 
 static inline void
 netlink_unlock_table(void)
 {
     if (atomic_dec_and_test(&nl_table_users))
         wake_up(&nl_table_wait);
 }
 
 struct netlink_compare_arg
 {
     possible_net_t pnet;
     u32 portid;
 };
 
 /* Doing sizeof directly may yield 4 extra bytes on 64-bit. */
 #define netlink_compare_arg_len \
     (offsetof(struct netlink_compare_arg, portid) + sizeof(u32))
 
 static inline int netlink_compare(struct rhashtable_compare_arg *arg,
                   const void *ptr)
 {
     const struct netlink_compare_arg *x = arg->key;
     const struct netlink_sock *nlk = ptr;
 
     return nlk->portid != x->portid ||
            !net_eq(sock_net(&nlk->sk), read_pnet(&x->pnet));
 }
 
 static void netlink_compare_arg_init(struct netlink_compare_arg *arg,
                      struct net *net, u32 portid)
 {
     memset(arg, 0, sizeof(*arg));
     write_pnet(&arg->pnet, net);
     arg->portid = portid;
 }
 
 static struct sock *__netlink_lookup(struct netlink_table *table, u32 portid,
                      struct net *net)
 {
     struct netlink_compare_arg arg;
 
     netlink_compare_arg_init(&arg, net, portid);
     return rhashtable_lookup_fast(&table->hash, &arg,
                       netlink_rhashtable_params);
 }
 
 static int __netlink_insert(struct netlink_table *table, struct sock *sk)
 {
     struct netlink_compare_arg arg;
 
     netlink_compare_arg_init(&arg, sock_net(sk), nlk_sk(sk)->portid);
     return rhashtable_lookup_insert_key(&table->hash, &arg,
                         &nlk_sk(sk)->node,
                         netlink_rhashtable_params);
 }
 
 static struct sock *netlink_lookup(struct net *net, int protocol, u32 portid)
 {
     struct netlink_table *table = &nl_table[protocol];
     struct sock *sk;
 
     rcu_read_lock();
     sk = __netlink_lookup(table, portid, net);
     if (sk)
         sock_hold(sk);
     rcu_read_unlock();
 
     return sk;
 }
 
 static const struct proto_ops netlink_ops;
 
 static void
 netlink_update_listeners(struct sock *sk)
 {
     struct netlink_table *tbl = &nl_table[sk->sk_protocol];
     unsigned long mask;
     unsigned int i;
     struct listeners *listeners;
 
     listeners = nl_deref_protected(tbl->listeners);
     if (!listeners)
         return;
 
     for (i = 0; i < NLGRPLONGS(tbl->groups); i++) {
         mask = 0;
         sk_for_each_bound(sk, &tbl->mc_list) {
             if (i < NLGRPLONGS(nlk_sk(sk)->ngroups))
                 mask |= nlk_sk(sk)->groups[i];
         }
         listeners->masks[i] = mask;
     }
     /* this function is only called with the netlink table "grabbed", which
      * makes sure updates are visible before bind or setsockopt return. */
 }
 
 static int netlink_insert(struct sock *sk, u32 portid)
 {
     struct netlink_table *table = &nl_table[sk->sk_protocol];
     int err;
 
     lock_sock(sk);
 
     err = nlk_sk(sk)->portid == portid ? 0 : -EBUSY;
     if (nlk_sk(sk)->bound)
         goto err;
 
     nlk_sk(sk)->portid = portid;
     sock_hold(sk);
 
     err = __netlink_insert(table, sk);
     if (err) {
         /* In case the hashtable backend returns with -EBUSY
          * from here, it must not escape to the caller.
          */
         if (unlikely(err == -EBUSY))
             err = -EOVERFLOW;
         if (err == -EEXIST)
             err = -EADDRINUSE;
         sock_put(sk);
         goto err;
     }
 
     /* We need to ensure that the socket is hashed and visible. */
     smp_wmb();
     /* Paired with lockless reads from netlink_bind(),
      * netlink_connect() and netlink_sendmsg().
      */
     WRITE_ONCE(nlk_sk(sk)->bound, portid);
 
 err:
     release_sock(sk);
     return err;
 }
 
 static void netlink_remove(struct sock *sk)
 {
     struct netlink_table *table;
 
     table = &nl_table[sk->sk_protocol];
     if (!rhashtable_remove_fast(&table->hash, &nlk_sk(sk)->node,
                     netlink_rhashtable_params)) {
         WARN_ON(refcount_read(&sk->sk_refcnt) == 1);
         __sock_put(sk);
     }
 
     netlink_table_grab();
     if (nlk_sk(sk)->subscriptions) {
         __sk_del_bind_node(sk);
         netlink_update_listeners(sk);
     }
     if (sk->sk_protocol == NETLINK_GENERIC)
         atomic_inc(&genl_sk_destructing_cnt);
     netlink_table_ungrab();
 }
 
 static struct proto netlink_proto = {
     .name     = "NETLINK",
     .owner    = THIS_MODULE,
     .obj_size = sizeof(struct netlink_sock),
 };
 
 static int __netlink_create(struct net *net, struct socket *sock,
                 struct mutex *cb_mutex, int protocol,
                 int kern)
 {
     struct sock *sk;
     struct netlink_sock *nlk;
 
     sock->ops = &netlink_ops;
 
     sk = sk_alloc(net, PF_NETLINK, GFP_KERNEL, &netlink_proto, kern);
     if (!sk)
         return -ENOMEM;
 
     sock_init_data(sock, sk);
 
     nlk = nlk_sk(sk);
     if (cb_mutex) {
         nlk->cb_mutex = cb_mutex;
     } else {
         nlk->cb_mutex = &nlk->cb_def_mutex;
         mutex_init(nlk->cb_mutex);
         lockdep_set_class_and_name(nlk->cb_mutex,
                        nlk_cb_mutex_keys + protocol,
                        nlk_cb_mutex_key_strings[protocol]);
     }
     init_waitqueue_head(&nlk->wait);
 
     sk->sk_destruct = netlink_sock_destruct;
     sk->sk_protocol = protocol;
     return 0;
 }
 
 static int netlink_create(struct net *net, struct socket *sock, int protocol,
               int kern)
 {
     struct module *module = NULL;
     struct mutex *cb_mutex;
     struct netlink_sock *nlk;
     int (*bind)(struct net *net, int group);
     void (*unbind)(struct net *net, int group);
     int err = 0;
 
     sock->state = SS_UNCONNECTED;
 
     if (sock->type != SOCK_RAW && sock->type != SOCK_DGRAM)
         return -ESOCKTNOSUPPORT;
 
     if (protocol < 0 || protocol >= MAX_LINKS)
         return -EPROTONOSUPPORT;
     protocol = array_index_nospec(protocol, MAX_LINKS);
 
     netlink_lock_table();
 #ifdef CONFIG_MODULES
     if (!nl_table[protocol].registered) {
         netlink_unlock_table();
         request_module("net-pf-%d-proto-%d", PF_NETLINK, protocol);
         netlink_lock_table();
     }
 #endif
     if (nl_table[protocol].registered &&
         try_module_get(nl_table[protocol].module))
         module = nl_table[protocol].module;
     else
         err = -EPROTONOSUPPORT;
     cb_mutex = nl_table[protocol].cb_mutex;
     bind = nl_table[protocol].bind;
     unbind = nl_table[protocol].unbind;
     netlink_unlock_table();
 
     if (err < 0)
         goto out;
 
     err = __netlink_create(net, sock, cb_mutex, protocol, kern);
     if (err < 0)
         goto out_module;
 
     sock_prot_inuse_add(net, &netlink_proto, 1);
 
     nlk = nlk_sk(sock->sk);
     nlk->module = module;
     nlk->netlink_bind = bind;
     nlk->netlink_unbind = unbind;
 out:
     return err;
 
 out_module:
     module_put(module);
     goto out;
 }
 
 static void deferred_put_nlk_sk(struct rcu_head *head)
 {
     struct netlink_sock *nlk = container_of(head, struct netlink_sock, rcu);
     struct sock *sk = &nlk->sk;
 
     kfree(nlk->groups);
     nlk->groups = NULL;
 
     if (!refcount_dec_and_test(&sk->sk_refcnt))
         return;
 
     if (nlk->cb_running && nlk->cb.done) {
         INIT_WORK(&nlk->work, netlink_sock_destruct_work);
         schedule_work(&nlk->work);
         return;
     }
 
     sk_free(sk);
 }
 
 static int netlink_release(struct socket *sock)
 {
     struct sock *sk = sock->sk;
     struct netlink_sock *nlk;
 
     if (!sk)
         return 0;
 
     netlink_remove(sk);
     sock_orphan(sk);
     nlk = nlk_sk(sk);
 
     /*
      * OK. Socket is unlinked, any packets that arrive now
      * will be purged.
      */
 
     /* must not acquire netlink_table_lock in any way again before unbind
      * and notifying genetlink is done as otherwise it might deadlock
      */
     if (nlk->netlink_unbind) {
         int i;
 
         for (i = 0; i < nlk->ngroups; i++)
             if (test_bit(i, nlk->groups))
                 nlk->netlink_unbind(sock_net(sk), i + 1);
     }
     if (sk->sk_protocol == NETLINK_GENERIC &&
         atomic_dec_return(&genl_sk_destructing_cnt) == 0)
         wake_up(&genl_sk_destructing_waitq);
 
     sock->sk = NULL;
     wake_up_interruptible_all(&nlk->wait);
 
     skb_queue_purge(&sk->sk_write_queue);
 
     if (nlk->portid && nlk->bound) {
         struct netlink_notify n = {
                         .net = sock_net(sk),
                         .protocol = sk->sk_protocol,
                         .portid = nlk->portid,
                       };
         blocking_notifier_call_chain(&netlink_chain,
                 NETLINK_URELEASE, &n);
     }
 
     module_put(nlk->module);
 
     if (netlink_is_kernel(sk)) {
         netlink_table_grab();
         BUG_ON(nl_table[sk->sk_protocol].registered == 0);
         if (--nl_table[sk->sk_protocol].registered == 0) {
             struct listeners *old;
 
             old = nl_deref_protected(nl_table[sk->sk_protocol].listeners);
             RCU_INIT_POINTER(nl_table[sk->sk_protocol].listeners, NULL);
             kfree_rcu(old, rcu);
             nl_table[sk->sk_protocol].module = NULL;
             nl_table[sk->sk_protocol].bind = NULL;
             nl_table[sk->sk_protocol].unbind = NULL;
             nl_table[sk->sk_protocol].flags = 0;
             nl_table[sk->sk_protocol].registered = 0;
         }
         netlink_table_ungrab();
     }
 
     sock_prot_inuse_add(sock_net(sk), &netlink_proto, -1);
     call_rcu(&nlk->rcu, deferred_put_nlk_sk);
     return 0;
 }
 
 static int netlink_autobind(struct socket *sock)
 {
     struct sock *sk = sock->sk;
     struct net *net = sock_net(sk);
     struct netlink_table *table = &nl_table[sk->sk_protocol];
     s32 portid = task_tgid_vnr(current);
     int err;
     s32 rover = -4096;
     bool ok;
 
 retry:
     cond_resched();
     rcu_read_lock();
     ok = !__netlink_lookup(table, portid, net);
     rcu_read_unlock();
     if (!ok) {
         /* Bind collision, search negative portid values. */
         if (rover == -4096)
             /* rover will be in range [S32_MIN, -4097] */
             rover = S32_MIN + prandom_u32_max(-4096 - S32_MIN);
         else if (rover >= -4096)
             rover = -4097;
         portid = rover--;
         goto retry;
     }
 
     err = netlink_insert(sk, portid);
     if (err == -EADDRINUSE)
         goto retry;
 
     /* If 2 threads race to autobind, that is fine.  */
     if (err == -EBUSY)
         err = 0;
 
     return err;
 }
 
 /**
  * __netlink_ns_capable - General netlink message capability test
  * @nsp: NETLINK_CB of the socket buffer holding a netlink command from userspace.
  * @user_ns: The user namespace of the capability to use
  * @cap: The capability to use
  *
  * Test to see if the opener of the socket we received the message
  * from had when the netlink socket was created and the sender of the
  * message has the capability @cap in the user namespace @user_ns.
  */
 bool __netlink_ns_capable(const struct netlink_skb_parms *nsp,
             struct user_namespace *user_ns, int cap)
 {
     return ((nsp->flags & NETLINK_SKB_DST) ||
         file_ns_capable(nsp->sk->sk_socket->file, user_ns, cap)) &&
         ns_capable(user_ns, cap);
 }
 EXPORT_SYMBOL(__netlink_ns_capable);
 
 /**
  * netlink_ns_capable - General netlink message capability test
  * @skb: socket buffer holding a netlink command from userspace
  * @user_ns: The user namespace of the capability to use
  * @cap: The capability to use
  *
  * Test to see if the opener of the socket we received the message
  * from had when the netlink socket was created and the sender of the
  * message has the capability @cap in the user namespace @user_ns.
  */
 bool netlink_ns_capable(const struct sk_buff *skb,
             struct user_namespace *user_ns, int cap)
 {
     return __netlink_ns_capable(&NETLINK_CB(skb), user_ns, cap);
 }
 EXPORT_SYMBOL(netlink_ns_capable);
 
 /**
  * netlink_capable - Netlink global message capability test
  * @skb: socket buffer holding a netlink command from userspace
  * @cap: The capability to use
  *
  * Test to see if the opener of the socket we received the message
  * from had when the netlink socket was created and the sender of the
  * message has the capability @cap in all user namespaces.
  */
 bool netlink_capable(const struct sk_buff *skb, int cap)
 {
     return netlink_ns_capable(skb, &init_user_ns, cap);
 }
 EXPORT_SYMBOL(netlink_capable);
 
 /**
  * netlink_net_capable - Netlink network namespace message capability test
  * @skb: socket buffer holding a netlink command from userspace
  * @cap: The capability to use
  *
  * Test to see if the opener of the socket we received the message
  * from had when the netlink socket was created and the sender of the
  * message has the capability @cap over the network namespace of
  * the socket we received the message from.
  */
 bool netlink_net_capable(const struct sk_buff *skb, int cap)
 {
     return netlink_ns_capable(skb, sock_net(skb->sk)->user_ns, cap);
 }
 EXPORT_SYMBOL(netlink_net_capable);
 
 static inline int netlink_allowed(const struct socket *sock, unsigned int flag)
 {
     return (nl_table[sock->sk->sk_protocol].flags & flag) ||
         ns_capable(sock_net(sock->sk)->user_ns, CAP_NET_ADMIN);
 }
 
 static void
 netlink_update_subscriptions(struct sock *sk, unsigned int subscriptions)
 {
     struct netlink_sock *nlk = nlk_sk(sk);
 
     if (nlk->subscriptions && !subscriptions)
         __sk_del_bind_node(sk);
     else if (!nlk->subscriptions && subscriptions)
         sk_add_bind_node(sk, &nl_table[sk->sk_protocol].mc_list);
     nlk->subscriptions = subscriptions;
 }
 
 static int netlink_realloc_groups(struct sock *sk)
 {
     struct netlink_sock *nlk = nlk_sk(sk);
     unsigned int groups;
     unsigned long *new_groups;
     int err = 0;
 
     netlink_table_grab();
 
     groups = nl_table[sk->sk_protocol].groups;
     if (!nl_table[sk->sk_protocol].registered) {
         err = -ENOENT;
         goto out_unlock;
     }
 
     if (nlk->ngroups >= groups)
         goto out_unlock;
 
     new_groups = krealloc(nlk->groups, NLGRPSZ(groups), GFP_ATOMIC);
     if (new_groups == NULL) {
         err = -ENOMEM;
         goto out_unlock;
     }
     memset((char *)new_groups + NLGRPSZ(nlk->ngroups), 0,
            NLGRPSZ(groups) - NLGRPSZ(nlk->ngroups));
 
     nlk->groups = new_groups;
     nlk->ngroups = groups;
  out_unlock:
     netlink_table_ungrab();
     return err;
 }
 
 static void netlink_undo_bind(int group, long unsigned int groups,
                   struct sock *sk)
 {
     struct netlink_sock *nlk = nlk_sk(sk);
     int undo;
 
     if (!nlk->netlink_unbind)
         return;
 
     for (undo = 0; undo < group; undo++)
         if (test_bit(undo, &groups))
             nlk->netlink_unbind(sock_net(sk), undo + 1);
 }
 
 static int netlink_bind(struct socket *sock, struct sockaddr *addr,
             int addr_len)
 {
     struct sock *sk = sock->sk;
     struct net *net = sock_net(sk);
     struct netlink_sock *nlk = nlk_sk(sk);
     struct sockaddr_nl *nladdr = (struct sockaddr_nl *)addr;
     int err = 0;
     unsigned long groups;
     bool bound;
 
     if (addr_len < sizeof(struct sockaddr_nl))
         return -EINVAL;
 
     if (nladdr->nl_family != AF_NETLINK)
         return -EINVAL;
     groups = nladdr->nl_groups;
 
     /* Only superuser is allowed to listen multicasts */
     if (groups) {
         if (!netlink_allowed(sock, NL_CFG_F_NONROOT_RECV))
             return -EPERM;
         err = netlink_realloc_groups(sk);
         if (err)
             return err;
     }
 
     if (nlk->ngroups < BITS_PER_LONG)
         groups &= (1UL << nlk->ngroups) - 1;
 
     /* Paired with WRITE_ONCE() in netlink_insert() */
     bound = READ_ONCE(nlk->bound);
     if (bound) {
         /* Ensure nlk->portid is up-to-date. */
         smp_rmb();
 
         if (nladdr->nl_pid != nlk->portid)
             return -EINVAL;
     }
 
     if (nlk->netlink_bind && groups) {
         int group;
 
         /* nl_groups is a u32, so cap the maximum groups we can bind */
         for (group = 0; group < BITS_PER_TYPE(u32); group++) {
             if (!test_bit(group, &groups))
                 continue;
             err = nlk->netlink_bind(net, group + 1);
             if (!err)
                 continue;
             netlink_undo_bind(group, groups, sk);
             return err;
         }
     }
 
     /* No need for barriers here as we return to user-space without
      * using any of the bound attributes.
      */
     netlink_lock_table();
     if (!bound) {
         err = nladdr->nl_pid ?
             netlink_insert(sk, nladdr->nl_pid) :
             netlink_autobind(sock);
         if (err) {
             netlink_undo_bind(BITS_PER_TYPE(u32), groups, sk);
             goto unlock;
         }
     }
 
     if (!groups && (nlk->groups == NULL || !(u32)nlk->groups[0]))
         goto unlock;
     netlink_unlock_table();
 
     netlink_table_grab();
     netlink_update_subscriptions(sk, nlk->subscriptions +
                      hweight32(groups) -
                      hweight32(nlk->groups[0]));
     nlk->groups[0] = (nlk->groups[0] & ~0xffffffffUL) | groups;
     netlink_update_listeners(sk);
     netlink_table_ungrab();
 
     return 0;
 
 unlock:
     netlink_unlock_table();
     return err;
 }
 
 static int netlink_connect(struct socket *sock, struct sockaddr *addr,
                int alen, int flags)
 {
     int err = 0;
     struct sock *sk = sock->sk;
     struct netlink_sock *nlk = nlk_sk(sk);
     struct sockaddr_nl *nladdr = (struct sockaddr_nl *)addr;
 
     if (alen < sizeof(addr->sa_family))
         return -EINVAL;
 
     if (addr->sa_family == AF_UNSPEC) {
         sk->sk_state    = NETLINK_UNCONNECTED;
         nlk->dst_portid = 0;
         nlk->dst_group  = 0;
         return 0;
     }
     if (addr->sa_family != AF_NETLINK)
         return -EINVAL;
 
     if (alen < sizeof(struct sockaddr_nl))
         return -EINVAL;
 
     if ((nladdr->nl_groups || nladdr->nl_pid) &&
         !netlink_allowed(sock, NL_CFG_F_NONROOT_SEND))
         return -EPERM;
 
     /* No need for barriers here as we return to user-space without
      * using any of the bound attributes.
      * Paired with WRITE_ONCE() in netlink_insert().
      */
     if (!READ_ONCE(nlk->bound))
         err = netlink_autobind(sock);
 
     if (err == 0) {
         sk->sk_state    = NETLINK_CONNECTED;
         nlk->dst_portid = nladdr->nl_pid;
         nlk->dst_group  = ffs(nladdr->nl_groups);
     }
 
     return err;
 }
 
 static int netlink_getname(struct socket *sock, struct sockaddr *addr,
                int peer)
 {
     struct sock *sk = sock->sk;
     struct netlink_sock *nlk = nlk_sk(sk);
     DECLARE_SOCKADDR(struct sockaddr_nl *, nladdr, addr);
 
     nladdr->nl_family = AF_NETLINK;
     nladdr->nl_pad = 0;
 
     if (peer) {
         nladdr->nl_pid = nlk->dst_portid;
         nladdr->nl_groups = netlink_group_mask(nlk->dst_group);
     } else {
         nladdr->nl_pid = nlk->portid;
         netlink_lock_table();
         nladdr->nl_groups = nlk->groups ? nlk->groups[0] : 0;
         netlink_unlock_table();
     }
     return sizeof(*nladdr);
 }
 
 static int netlink_ioctl(struct socket *sock, unsigned int cmd,
              unsigned long arg)
 {
     /* try to hand this ioctl down to the NIC drivers.
      */
     return -ENOIOCTLCMD;
 }
 
 static struct sock *netlink_getsockbyportid(struct sock *ssk, u32 portid)
 {
     struct sock *sock;
     struct netlink_sock *nlk;
 
     sock = netlink_lookup(sock_net(ssk), ssk->sk_protocol, portid);
     if (!sock)
         return ERR_PTR(-ECONNREFUSED);
 
     /* Don't bother queuing skb if kernel socket has no input function */
     nlk = nlk_sk(sock);
     if (sock->sk_state == NETLINK_CONNECTED &&
         nlk->dst_portid != nlk_sk(ssk)->portid) {
         sock_put(sock);
         return ERR_PTR(-ECONNREFUSED);
     }
     return sock;
 }
 
 struct sock *netlink_getsockbyfilp(struct file *filp)
 {
     struct inode *inode = file_inode(filp);
     struct sock *sock;
 
     if (!S_ISSOCK(inode->i_mode))
         return ERR_PTR(-ENOTSOCK);
 
     sock = SOCKET_I(inode)->sk;
     if (sock->sk_family != AF_NETLINK)
         return ERR_PTR(-EINVAL);
 
     sock_hold(sock);
     return sock;
 }
 
 static struct sk_buff *netlink_alloc_large_skb(unsigned int size,
                            int broadcast)
 {
     struct sk_buff *skb;
     void *data;
 
     if (size <= NLMSG_GOODSIZE || broadcast)
         return alloc_skb(size, GFP_KERNEL);
 
     size = SKB_DATA_ALIGN(size) +
            SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
 
     data = vmalloc(size);
     if (data == NULL)
         return NULL;
 
     skb = __build_skb(data, size);
     if (skb == NULL)
         vfree(data);
     else
         skb->destructor = netlink_skb_destructor;
 
     return skb;
 }
 
 /*
  * Attach a skb to a netlink socket.
  * The caller must hold a reference to the destination socket. On error, the
  * reference is dropped. The skb is not send to the destination, just all
  * all error checks are performed and memory in the queue is reserved.
  * Return values:
  * < 0: error. skb freed, reference to sock dropped.
  * 0: continue
  * 1: repeat lookup - reference dropped while waiting for socket memory.
  */
 int netlink_attachskb(struct sock *sk, struct sk_buff *skb,
               long *timeo, struct sock *ssk)
 {
     struct netlink_sock *nlk;
 
     nlk = nlk_sk(sk);
 
     if ((atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
          test_bit(NETLINK_S_CONGESTED, &nlk->state))) {
         DECLARE_WAITQUEUE(wait, current);
         if (!*timeo) {
             if (!ssk || netlink_is_kernel(ssk))
                 netlink_overrun(sk);
             sock_put(sk);
             kfree_skb(skb);
             return -EAGAIN;
         }
 
         __set_current_state(TASK_INTERRUPTIBLE);
         add_wait_queue(&nlk->wait, &wait);
 
         if ((atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
              test_bit(NETLINK_S_CONGESTED, &nlk->state)) &&
             !sock_flag(sk, SOCK_DEAD))
             *timeo = schedule_timeout(*timeo);
 
         __set_current_state(TASK_RUNNING);
         remove_wait_queue(&nlk->wait, &wait);
         sock_put(sk);
 
         if (signal_pending(current)) {
             kfree_skb(skb);
             return sock_intr_errno(*timeo);
         }
         return 1;
     }
     netlink_skb_set_owner_r(skb, sk);
     return 0;
 }
 
 static int __netlink_sendskb(struct sock *sk, struct sk_buff *skb)
 {
     int len = skb->len;
 
     netlink_deliver_tap(sock_net(sk), skb);
 
     skb_queue_tail(&sk->sk_receive_queue, skb);
     sk->sk_data_ready(sk);
     return len;
 }
 
 int netlink_sendskb(struct sock *sk, struct sk_buff *skb)
 {
     int len = __netlink_sendskb(sk, skb);
 
     sock_put(sk);
     return len;
 }
 
 void netlink_detachskb(struct sock *sk, struct sk_buff *skb)
 {
     kfree_skb(skb);
     sock_put(sk);
 }
 
 static struct sk_buff *netlink_trim(struct sk_buff *skb, gfp_t allocation)
 {
     int delta;
 
     WARN_ON(skb->sk != NULL);
     delta = skb->end - skb->tail;
     if (is_vmalloc_addr(skb->head) || delta * 2 < skb->truesize)
         return skb;
 
     if (skb_shared(skb)) {
         struct sk_buff *nskb = skb_clone(skb, allocation);
         if (!nskb)
             return skb;
         consume_skb(skb);
         skb = nskb;
     }
 
     pskb_expand_head(skb, 0, -delta,
              (allocation & ~__GFP_DIRECT_RECLAIM) |
              __GFP_NOWARN | __GFP_NORETRY);
     return skb;
 }
 
 static int netlink_unicast_kernel(struct sock *sk, struct sk_buff *skb,
                   struct sock *ssk)
 {
     int ret;
     struct netlink_sock *nlk = nlk_sk(sk);
 
     ret = -ECONNREFUSED;
     if (nlk->netlink_rcv != NULL) {
         ret = skb->len;
         netlink_skb_set_owner_r(skb, sk);
         NETLINK_CB(skb).sk = ssk;
         netlink_deliver_tap_kernel(sk, ssk, skb);
         nlk->netlink_rcv(skb);
         consume_skb(skb);
     } else {
         kfree_skb(skb);
     }
     sock_put(sk);
     return ret;
 }
 
 int netlink_unicast(struct sock *ssk, struct sk_buff *skb,
             u32 portid, int nonblock)
 {
     struct sock *sk;
     int err;
     long timeo;
 
     skb = netlink_trim(skb, gfp_any());
 
     timeo = sock_sndtimeo(ssk, nonblock);
 retry:
     sk = netlink_getsockbyportid(ssk, portid);
     if (IS_ERR(sk)) {
         kfree_skb(skb);
         return PTR_ERR(sk);
     }
     if (netlink_is_kernel(sk))
         return netlink_unicast_kernel(sk, skb, ssk);
 
     if (sk_filter(sk, skb)) {
         err = skb->len;
         kfree_skb(skb);
         sock_put(sk);
         return err;
     }
 
     err = netlink_attachskb(sk, skb, &timeo, ssk);
     if (err == 1)
         goto retry;
     if (err)
         return err;
 
     return netlink_sendskb(sk, skb);
 }
 EXPORT_SYMBOL(netlink_unicast);
 
 int netlink_has_listeners(struct sock *sk, unsigned int group)
 {
     int res = 0;
     struct listeners *listeners;
 
     BUG_ON(!netlink_is_kernel(sk));
 
     rcu_read_lock();
     listeners = rcu_dereference(nl_table[sk->sk_protocol].listeners);
 
     if (listeners && group - 1 < nl_table[sk->sk_protocol].groups)
         res = test_bit(group - 1, listeners->masks);
 
     rcu_read_unlock();
 
     return res;
 }
 EXPORT_SYMBOL_GPL(netlink_has_listeners);
 
 bool netlink_strict_get_check(struct sk_buff *skb)
 {
     const struct netlink_sock *nlk = nlk_sk(NETLINK_CB(skb).sk);
 
     return nlk->flags & NETLINK_F_STRICT_CHK;
 }
 EXPORT_SYMBOL_GPL(netlink_strict_get_check);
 
 static int netlink_broadcast_deliver(struct sock *sk, struct sk_buff *skb)
 {
     struct netlink_sock *nlk = nlk_sk(sk);
 
     if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf &&
         !test_bit(NETLINK_S_CONGESTED, &nlk->state)) {
         netlink_skb_set_owner_r(skb, sk);
         __netlink_sendskb(sk, skb);
         return atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1);
     }
     return -1;
 }
 
 struct netlink_broadcast_data {
     struct sock *exclude_sk;
     struct net *net;
     u32 portid;
     u32 group;
     int failure;
     int delivery_failure;
     int congested;
     int delivered;
     gfp_t allocation;
     struct sk_buff *skb, *skb2;
 };
 
 static void do_one_broadcast(struct sock *sk,
                     struct netlink_broadcast_data *p)
 {
     struct netlink_sock *nlk = nlk_sk(sk);
     int val;
 
     if (p->exclude_sk == sk)
         return;
 
     if (nlk->portid == p->portid || p->group - 1 >= nlk->ngroups ||
         !test_bit(p->group - 1, nlk->groups))
         return;
 
     if (!net_eq(sock_net(sk), p->net)) {
         if (!(nlk->flags & NETLINK_F_LISTEN_ALL_NSID))
             return;
 
         if (!peernet_has_id(sock_net(sk), p->net))
             return;
 
         if (!file_ns_capable(sk->sk_socket->file, p->net->user_ns,
                      CAP_NET_BROADCAST))
             return;
     }
 
     if (p->failure) {
         netlink_overrun(sk);
         return;
     }
 
     sock_hold(sk);
     if (p->skb2 == NULL) {
         if (skb_shared(p->skb)) {
             p->skb2 = skb_clone(p->skb, p->allocation);
         } else {
             p->skb2 = skb_get(p->skb);
             /*
              * skb ownership may have been set when
              * delivered to a previous socket.
              */
             skb_orphan(p->skb2);
         }
     }
     if (p->skb2 == NULL) {
         netlink_overrun(sk);
         /* Clone failed. Notify ALL listeners. */
         p->failure = 1;
         if (nlk->flags & NETLINK_F_BROADCAST_SEND_ERROR)
             p->delivery_failure = 1;
         goto out;
     }
     if (sk_filter(sk, p->skb2)) {
         kfree_skb(p->skb2);
         p->skb2 = NULL;
         goto out;
     }
     NETLINK_CB(p->skb2).nsid = peernet2id(sock_net(sk), p->net);
     if (NETLINK_CB(p->skb2).nsid != NETNSA_NSID_NOT_ASSIGNED)
         NETLINK_CB(p->skb2).nsid_is_set = true;
     val = netlink_broadcast_deliver(sk, p->skb2);
     if (val < 0) {
         netlink_overrun(sk);
         if (nlk->flags & NETLINK_F_BROADCAST_SEND_ERROR)
             p->delivery_failure = 1;
     } else {
         p->congested |= val;
         p->delivered = 1;
         p->skb2 = NULL;
     }
 out:
     sock_put(sk);
 }
 
 int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, u32 portid,
               u32 group, gfp_t allocation)
 {
     struct net *net = sock_net(ssk);
     struct netlink_broadcast_data info;
     struct sock *sk;
 
     skb = netlink_trim(skb, allocation);
 
     info.exclude_sk = ssk;
     info.net = net;
     info.portid = portid;
     info.group = group;
     info.failure = 0;
     info.delivery_failure = 0;
     info.congested = 0;
     info.delivered = 0;
     info.allocation = allocation;
     info.skb = skb;
     info.skb2 = NULL;
 
     /* While we sleep in clone, do not allow to change socket list */
 
     netlink_lock_table();
 
     sk_for_each_bound(sk, &nl_table[ssk->sk_protocol].mc_list)
         do_one_broadcast(sk, &info);
 
     consume_skb(skb);
 
     netlink_unlock_table();
 
     if (info.delivery_failure) {
         kfree_skb(info.skb2);
         return -ENOBUFS;
     }
     consume_skb(info.skb2);
 
     if (info.delivered) {
         if (info.congested && gfpflags_allow_blocking(allocation))
             yield();
         return 0;
     }
     return -ESRCH;
 }
 EXPORT_SYMBOL(netlink_broadcast);
 
 struct netlink_set_err_data {
     struct sock *exclude_sk;
     u32 portid;
     u32 group;
     int code;
 };
 
 static int do_one_set_err(struct sock *sk, struct netlink_set_err_data *p)
 {
     struct netlink_sock *nlk = nlk_sk(sk);
     int ret = 0;
 
     if (sk == p->exclude_sk)
         goto out;
 
     if (!net_eq(sock_net(sk), sock_net(p->exclude_sk)))
         goto out;
 
     if (nlk->portid == p->portid || p->group - 1 >= nlk->ngroups ||
         !test_bit(p->group - 1, nlk->groups))
         goto out;
 
     if (p->code == ENOBUFS && nlk->flags & NETLINK_F_RECV_NO_ENOBUFS) {
         ret = 1;
         goto out;
     }
 
     sk->sk_err = p->code;
     sk_error_report(sk);
 out:
     return ret;
 }
 
 /**
  * netlink_set_err - report error to broadcast listeners
  * @ssk: the kernel netlink socket, as returned by netlink_kernel_create()
  * @portid: the PORTID of a process that we want to skip (if any)
  * @group: the broadcast group that will notice the error
  * @code: error code, must be negative (as usual in kernelspace)
  *
  * This function returns the number of broadcast listeners that have set the
  * NETLINK_NO_ENOBUFS socket option.
  */
 int netlink_set_err(struct sock *ssk, u32 portid, u32 group, int code)
 {
     struct netlink_set_err_data info;
     struct sock *sk;
     int ret = 0;
 
     info.exclude_sk = ssk;
     info.portid = portid;
     info.group = group;
     /* sk->sk_err wants a positive error value */
     info.code = -code;
 
     read_lock(&nl_table_lock);
 
     sk_for_each_bound(sk, &nl_table[ssk->sk_protocol].mc_list)
         ret += do_one_set_err(sk, &info);
 
     read_unlock(&nl_table_lock);
     return ret;
 }
 EXPORT_SYMBOL(netlink_set_err);
 
 /* must be called with netlink table grabbed */
 static void netlink_update_socket_mc(struct netlink_sock *nlk,
                      unsigned int group,
                      int is_new)
 {
     int old, new = !!is_new, subscriptions;
 
     old = test_bit(group - 1, nlk->groups);
     subscriptions = nlk->subscriptions - old + new;
     if (new)
         __set_bit(group - 1, nlk->groups);
     else
         __clear_bit(group - 1, nlk->groups);
     netlink_update_subscriptions(&nlk->sk, subscriptions);
     netlink_update_listeners(&nlk->sk);
 }
 
 static int netlink_setsockopt(struct socket *sock, int level, int optname,
                   sockptr_t optval, unsigned int optlen)
 {
     struct sock *sk = sock->sk;
     struct netlink_sock *nlk = nlk_sk(sk);
     unsigned int val = 0;
     int err;
 
     if (level != SOL_NETLINK)
         return -ENOPROTOOPT;
 
     if (optlen >= sizeof(int) &&
         copy_from_sockptr(&val, optval, sizeof(val)))
         return -EFAULT;
 
     switch (optname) {
     case NETLINK_PKTINFO:
         if (val)
             nlk->flags |= NETLINK_F_RECV_PKTINFO;
         else
             nlk->flags &= ~NETLINK_F_RECV_PKTINFO;
         err = 0;
         break;
     case NETLINK_ADD_MEMBERSHIP:
     case NETLINK_DROP_MEMBERSHIP: {
         if (!netlink_allowed(sock, NL_CFG_F_NONROOT_RECV))
             return -EPERM;
         err = netlink_realloc_groups(sk);
         if (err)
             return err;
         if (!val || val - 1 >= nlk->ngroups)
             return -EINVAL;
         if (optname == NETLINK_ADD_MEMBERSHIP && nlk->netlink_bind) {
             err = nlk->netlink_bind(sock_net(sk), val);
             if (err)
                 return err;
         }
         netlink_table_grab();
         netlink_update_socket_mc(nlk, val,
                      optname == NETLINK_ADD_MEMBERSHIP);
         netlink_table_ungrab();
         if (optname == NETLINK_DROP_MEMBERSHIP && nlk->netlink_unbind)
             nlk->netlink_unbind(sock_net(sk), val);
 
         err = 0;
         break;
     }
     case NETLINK_BROADCAST_ERROR:
         if (val)
             nlk->flags |= NETLINK_F_BROADCAST_SEND_ERROR;
         else
             nlk->flags &= ~NETLINK_F_BROADCAST_SEND_ERROR;
         err = 0;
         break;
     case NETLINK_NO_ENOBUFS:
         if (val) {
             nlk->flags |= NETLINK_F_RECV_NO_ENOBUFS;
             clear_bit(NETLINK_S_CONGESTED, &nlk->state);
             wake_up_interruptible(&nlk->wait);
         } else {
             nlk->flags &= ~NETLINK_F_RECV_NO_ENOBUFS;
         }
         err = 0;
         break;
     case NETLINK_LISTEN_ALL_NSID:
         if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_BROADCAST))
             return -EPERM;
 
         if (val)
             nlk->flags |= NETLINK_F_LISTEN_ALL_NSID;
         else
             nlk->flags &= ~NETLINK_F_LISTEN_ALL_NSID;
         err = 0;
         break;
     case NETLINK_CAP_ACK:
         if (val)
             nlk->flags |= NETLINK_F_CAP_ACK;
         else
             nlk->flags &= ~NETLINK_F_CAP_ACK;
         err = 0;
         break;
     case NETLINK_EXT_ACK:
         if (val)
             nlk->flags |= NETLINK_F_EXT_ACK;
         else
             nlk->flags &= ~NETLINK_F_EXT_ACK;
         err = 0;
         break;
     case NETLINK_GET_STRICT_CHK:
         if (val)
             nlk->flags |= NETLINK_F_STRICT_CHK;
         else
             nlk->flags &= ~NETLINK_F_STRICT_CHK;
         err = 0;
         break;
     default:
         err = -ENOPROTOOPT;
     }
     return err;
 }
 
 static int netlink_getsockopt(struct socket *sock, int level, int optname,
                   char __user *optval, int __user *optlen)
 {
     struct sock *sk = sock->sk;
     struct netlink_sock *nlk = nlk_sk(sk);
     int len, val, err;
 
     if (level != SOL_NETLINK)
         return -ENOPROTOOPT;
 
     if (get_user(len, optlen))
         return -EFAULT;
     if (len < 0)
         return -EINVAL;
 
     switch (optname) {
     case NETLINK_PKTINFO:
         if (len < sizeof(int))
             return -EINVAL;
         len = sizeof(int);
         val = nlk->flags & NETLINK_F_RECV_PKTINFO ? 1 : 0;
         if (put_user(len, optlen) ||
             put_user(val, optval))
             return -EFAULT;
         err = 0;
         break;
     case NETLINK_BROADCAST_ERROR:
         if (len < sizeof(int))
             return -EINVAL;
         len = sizeof(int);
         val = nlk->flags & NETLINK_F_BROADCAST_SEND_ERROR ? 1 : 0;
         if (put_user(len, optlen) ||
             put_user(val, optval))
             return -EFAULT;
         err = 0;
         break;
     case NETLINK_NO_ENOBUFS:
         if (len < sizeof(int))
             return -EINVAL;
         len = sizeof(int);
         val = nlk->flags & NETLINK_F_RECV_NO_ENOBUFS ? 1 : 0;
         if (put_user(len, optlen) ||
             put_user(val, optval))
             return -EFAULT;
         err = 0;
         break;
     case NETLINK_LIST_MEMBERSHIPS: {
         int pos, idx, shift;
 
         err = 0;
         netlink_lock_table();
         for (pos = 0; pos * 8 < nlk->ngroups; pos += sizeof(u32)) {
             if (len - pos < sizeof(u32))
                 break;
 
             idx = pos / sizeof(unsigned long);
             shift = (pos % sizeof(unsigned long)) * 8;
             if (put_user((u32)(nlk->groups[idx] >> shift),
                      (u32 __user *)(optval + pos))) {
                 err = -EFAULT;
                 break;
             }
         }
         if (put_user(ALIGN(nlk->ngroups / 8, sizeof(u32)), optlen))
             err = -EFAULT;
         netlink_unlock_table();
         break;
     }
     case NETLINK_CAP_ACK:
         if (len < sizeof(int))
             return -EINVAL;
         len = sizeof(int);
         val = nlk->flags & NETLINK_F_CAP_ACK ? 1 : 0;
         if (put_user(len, optlen) ||
             put_user(val, optval))
             return -EFAULT;
         err = 0;
         break;
     case NETLINK_EXT_ACK:
         if (len < sizeof(int))
             return -EINVAL;
         len = sizeof(int);
         val = nlk->flags & NETLINK_F_EXT_ACK ? 1 : 0;
         if (put_user(len, optlen) || put_user(val, optval))
             return -EFAULT;
         err = 0;
         break;
     case NETLINK_GET_STRICT_CHK:
         if (len < sizeof(int))
             return -EINVAL;
         len = sizeof(int);
         val = nlk->flags & NETLINK_F_STRICT_CHK ? 1 : 0;
         if (put_user(len, optlen) || put_user(val, optval))
             return -EFAULT;
         err = 0;
         break;
     default:
         err = -ENOPROTOOPT;
     }
     return err;
 }
 
 static void netlink_cmsg_recv_pktinfo(struct msghdr *msg, struct sk_buff *skb)
 {
     struct nl_pktinfo info;
 
     info.group = NETLINK_CB(skb).dst_group;
     put_cmsg(msg, SOL_NETLINK, NETLINK_PKTINFO, sizeof(info), &info);
 }
 
 static void netlink_cmsg_listen_all_nsid(struct sock *sk, struct msghdr *msg,
                      struct sk_buff *skb)
 {
     if (!NETLINK_CB(skb).nsid_is_set)
         return;
 
     put_cmsg(msg, SOL_NETLINK, NETLINK_LISTEN_ALL_NSID, sizeof(int),
          &NETLINK_CB(skb).nsid);
 }
 
 static int netlink_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
 {
     struct sock *sk = sock->sk;
     struct netlink_sock *nlk = nlk_sk(sk);
     DECLARE_SOCKADDR(struct sockaddr_nl *, addr, msg->msg_name);
     u32 dst_portid;
     u32 dst_group;
     struct sk_buff *skb;
     int err;
     struct scm_cookie scm;
     u32 netlink_skb_flags = 0;
 
     if (msg->msg_flags & MSG_OOB)
         return -EOPNOTSUPP;
 
     if (len == 0) {
         pr_warn_once("Zero length message leads to an empty skb\n");
         return -ENODATA;
     }
 
     err = scm_send(sock, msg, &scm, true);
     if (err < 0)
         return err;
 
     if (msg->msg_namelen) {
         err = -EINVAL;
         if (msg->msg_namelen < sizeof(struct sockaddr_nl))
             goto out;
         if (addr->nl_family != AF_NETLINK)
             goto out;
         dst_portid = addr->nl_pid;
         dst_group = ffs(addr->nl_groups);
         err =  -EPERM;
         if ((dst_group || dst_portid) &&
             !netlink_allowed(sock, NL_CFG_F_NONROOT_SEND))
             goto out;
         netlink_skb_flags |= NETLINK_SKB_DST;
     } else {
         dst_portid = nlk->dst_portid;
         dst_group = nlk->dst_group;
     }
 
     /* Paired with WRITE_ONCE() in netlink_insert() */
     if (!READ_ONCE(nlk->bound)) {
         err = netlink_autobind(sock);
         if (err)
             goto out;
     } else {
         /* Ensure nlk is hashed and visible. */
         smp_rmb();
     }
 
     err = -EMSGSIZE;
     if (len > sk->sk_sndbuf - 32)
         goto out;
     err = -ENOBUFS;
     skb = netlink_alloc_large_skb(len, dst_group);
     if (skb == NULL)
         goto out;
 
     NETLINK_CB(skb).portid  = nlk->portid;
     NETLINK_CB(skb).dst_group = dst_group;
     NETLINK_CB(skb).creds   = scm.creds;
     NETLINK_CB(skb).flags   = netlink_skb_flags;
 
     err = -EFAULT;
     if (memcpy_from_msg(skb_put(skb, len), msg, len)) {
         kfree_skb(skb);
         goto out;
     }
 
     err = security_netlink_send(sk, skb);
     if (err) {
         kfree_skb(skb);
         goto out;
     }
 
     if (dst_group) {
         refcount_inc(&skb->users);
         netlink_broadcast(sk, skb, dst_portid, dst_group, GFP_KERNEL);
     }
     err = netlink_unicast(sk, skb, dst_portid, msg->msg_flags & MSG_DONTWAIT);
 
 out:
     scm_destroy(&scm);
     return err;
 }
 
 static int netlink_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
                int flags)
 {
     struct scm_cookie scm;
     struct sock *sk = sock->sk;
     struct netlink_sock *nlk = nlk_sk(sk);
     size_t copied;
     struct sk_buff *skb, *data_skb;
     int err, ret;
 
     if (flags & MSG_OOB)
         return -EOPNOTSUPP;
 
     copied = 0;
 
     skb = skb_recv_datagram(sk, flags, &err);
     if (skb == NULL)
         goto out;
 
     data_skb = skb;
 
 #ifdef CONFIG_COMPAT_NETLINK_MESSAGES
     if (unlikely(skb_shinfo(skb)->frag_list)) {
         /*
          * If this skb has a frag_list, then here that means that we
          * will have to use the frag_list skb's data for compat tasks
          * and the regular skb's data for normal (non-compat) tasks.
          *
          * If we need to send the compat skb, assign it to the
          * 'data_skb' variable so that it will be used below for data
          * copying. We keep 'skb' for everything else, including
          * freeing both later.
          */
         if (flags & MSG_CMSG_COMPAT)
             data_skb = skb_shinfo(skb)->frag_list;
     }
 #endif
 
     /* Record the max length of recvmsg() calls for future allocations */
     nlk->max_recvmsg_len = max(nlk->max_recvmsg_len, len);
     nlk->max_recvmsg_len = min_t(size_t, nlk->max_recvmsg_len,
                      SKB_WITH_OVERHEAD(32768));
 
     copied = data_skb->len;
     if (len < copied) {
         msg->msg_flags |= MSG_TRUNC;
         copied = len;
     }
 
     err = skb_copy_datagram_msg(data_skb, 0, msg, copied);
 
     if (msg->msg_name) {
         DECLARE_SOCKADDR(struct sockaddr_nl *, addr, msg->msg_name);
         addr->nl_family = AF_NETLINK;
         addr->nl_pad    = 0;
         addr->nl_pid    = NETLINK_CB(skb).portid;
         addr->nl_groups = netlink_group_mask(NETLINK_CB(skb).dst_group);
         msg->msg_namelen = sizeof(*addr);
     }
 
     if (nlk->flags & NETLINK_F_RECV_PKTINFO)
         netlink_cmsg_recv_pktinfo(msg, skb);
     if (nlk->flags & NETLINK_F_LISTEN_ALL_NSID)
         netlink_cmsg_listen_all_nsid(sk, msg, skb);
 
     memset(&scm, 0, sizeof(scm));
     scm.creds = *NETLINK_CREDS(skb);
     if (flags & MSG_TRUNC)
         copied = data_skb->len;
 
     skb_free_datagram(sk, skb);
 
     if (nlk->cb_running &&
         atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf / 2) {
         ret = netlink_dump(sk);
         if (ret) {
             sk->sk_err = -ret;
             sk_error_report(sk);
         }
     }
 
     scm_recv(sock, msg, &scm, flags);
 out:
     netlink_rcv_wake(sk);
     return err ? : copied;
 }
 
 static void netlink_data_ready(struct sock *sk)
 {
     BUG();
 }
 
 /*
  *  We export these functions to other modules. They provide a
  *  complete set of kernel non-blocking support for message
  *  queueing.
  */
 
 struct sock *
 __netlink_kernel_create(struct net *net, int unit, struct module *module,
             struct netlink_kernel_cfg *cfg)
 {
     struct socket *sock;
     struct sock *sk;
     struct netlink_sock *nlk;
     struct listeners *listeners = NULL;
     struct mutex *cb_mutex = cfg ? cfg->cb_mutex : NULL;
     unsigned int groups;
 
     BUG_ON(!nl_table);
 
     if (unit < 0 || unit >= MAX_LINKS)
         return NULL;
 
     if (sock_create_lite(PF_NETLINK, SOCK_DGRAM, unit, &sock))
         return NULL;
 
     if (__netlink_create(net, sock, cb_mutex, unit, 1) < 0)
         goto out_sock_release_nosk;
 
     sk = sock->sk;
 
     if (!cfg || cfg->groups < 32)
         groups = 32;
     else
         groups = cfg->groups;
 
     listeners = kzalloc(sizeof(*listeners) + NLGRPSZ(groups), GFP_KERNEL);
     if (!listeners)
         goto out_sock_release;
 
     sk->sk_data_ready = netlink_data_ready;
     if (cfg && cfg->input)
         nlk_sk(sk)->netlink_rcv = cfg->input;
 
     if (netlink_insert(sk, 0))
         goto out_sock_release;
 
     nlk = nlk_sk(sk);
     nlk->flags |= NETLINK_F_KERNEL_SOCKET;
 
     netlink_table_grab();
     if (!nl_table[unit].registered) {
         nl_table[unit].groups = groups;
         rcu_assign_pointer(nl_table[unit].listeners, listeners);
         nl_table[unit].cb_mutex = cb_mutex;
         nl_table[unit].module = module;
         if (cfg) {
             nl_table[unit].bind = cfg->bind;
             nl_table[unit].unbind = cfg->unbind;
             nl_table[unit].flags = cfg->flags;
             if (cfg->compare)
                 nl_table[unit].compare = cfg->compare;
         }
         nl_table[unit].registered = 1;
     } else {
         kfree(listeners);
         nl_table[unit].registered++;
     }
     netlink_table_ungrab();
     return sk;
 
 out_sock_release:
     kfree(listeners);
     netlink_kernel_release(sk);
     return NULL;
 
 out_sock_release_nosk:
     sock_release(sock);
     return NULL;
 }
 EXPORT_SYMBOL(__netlink_kernel_create);
 
 void
 netlink_kernel_release(struct sock *sk)
 {
     if (sk == NULL || sk->sk_socket == NULL)
         return;
 
     sock_release(sk->sk_socket);
 }
 EXPORT_SYMBOL(netlink_kernel_release);
 
 int __netlink_change_ngroups(struct sock *sk, unsigned int groups)
 {
     struct listeners *new, *old;
     struct netlink_table *tbl = &nl_table[sk->sk_protocol];
 
     if (groups < 32)
         groups = 32;
 
     if (NLGRPSZ(tbl->groups) < NLGRPSZ(groups)) {
         new = kzalloc(sizeof(*new) + NLGRPSZ(groups), GFP_ATOMIC);
         if (!new)
             return -ENOMEM;
         old = nl_deref_protected(tbl->listeners);
         memcpy(new->masks, old->masks, NLGRPSZ(tbl->groups));
         rcu_assign_pointer(tbl->listeners, new);
 
         kfree_rcu(old, rcu);
     }
     tbl->groups = groups;
 
     return 0;
 }
 
 /**
  * netlink_change_ngroups - change number of multicast groups
  *
  * This changes the number of multicast groups that are available
  * on a certain netlink family. Note that it is not possible to
  * change the number of groups to below 32. Also note that it does
  * not implicitly call netlink_clear_multicast_users() when the
  * number of groups is reduced.
  *
  * @sk: The kernel netlink socket, as returned by netlink_kernel_create().
  * @groups: The new number of groups.
  */
 int netlink_change_ngroups(struct sock *sk, unsigned int groups)
 {
     int err;
 
     netlink_table_grab();
     err = __netlink_change_ngroups(sk, groups);
     netlink_table_ungrab();
 
     return err;
 }
 
 void __netlink_clear_multicast_users(struct sock *ksk, unsigned int group)
 {
     struct sock *sk;
     struct netlink_table *tbl = &nl_table[ksk->sk_protocol];
 
     sk_for_each_bound(sk, &tbl->mc_list)
         netlink_update_socket_mc(nlk_sk(sk), group, 0);
 }
 
 struct nlmsghdr *
 __nlmsg_put(struct sk_buff *skb, u32 portid, u32 seq, int type, int len, int flags)
 {
     struct nlmsghdr *nlh;
     int size = nlmsg_msg_size(len);
 
     nlh = skb_put(skb, NLMSG_ALIGN(size));
     nlh->nlmsg_type = type;
     nlh->nlmsg_len = size;
     nlh->nlmsg_flags = flags;
     nlh->nlmsg_pid = portid;
     nlh->nlmsg_seq = seq;
     if (!__builtin_constant_p(size) || NLMSG_ALIGN(size) - size != 0)
         memset(nlmsg_data(nlh) + len, 0, NLMSG_ALIGN(size) - size);
     return nlh;
 }
 EXPORT_SYMBOL(__nlmsg_put);
 
 /*
  * It looks a bit ugly.
  * It would be better to create kernel thread.
  */
 
 static int netlink_dump_done(struct netlink_sock *nlk, struct sk_buff *skb,
                  struct netlink_callback *cb,
                  struct netlink_ext_ack *extack)
 {
     struct nlmsghdr *nlh;
 
     nlh = nlmsg_put_answer(skb, cb, NLMSG_DONE, sizeof(nlk->dump_done_errno),
                    NLM_F_MULTI | cb->answer_flags);
     if (WARN_ON(!nlh))
         return -ENOBUFS;
 
     nl_dump_check_consistent(cb, nlh);
     memcpy(nlmsg_data(nlh), &nlk->dump_done_errno, sizeof(nlk->dump_done_errno));
 
     if (extack->_msg && nlk->flags & NETLINK_F_EXT_ACK) {
         nlh->nlmsg_flags |= NLM_F_ACK_TLVS;
         if (!nla_put_string(skb, NLMSGERR_ATTR_MSG, extack->_msg))
             nlmsg_end(skb, nlh);
     }
 
     return 0;
 }
 
 static int netlink_dump(struct sock *sk)
 {
     struct netlink_sock *nlk = nlk_sk(sk);
     struct netlink_ext_ack extack = {};
     struct netlink_callback *cb;
     struct sk_buff *skb = NULL;
     struct module *module;
     int err = -ENOBUFS;
     int alloc_min_size;
     int alloc_size;
 
     mutex_lock(nlk->cb_mutex);
     if (!nlk->cb_running) {
         err = -EINVAL;
         goto errout_skb;
     }
 
     if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
         goto errout_skb;
 
     /* NLMSG_GOODSIZE is small to avoid high order allocations being
      * required, but it makes sense to _attempt_ a 16K bytes allocation
      * to reduce number of system calls on dump operations, if user
      * ever provided a big enough buffer.
      */
     cb = &nlk->cb;
     alloc_min_size = max_t(int, cb->min_dump_alloc, NLMSG_GOODSIZE);
 
     if (alloc_min_size < nlk->max_recvmsg_len) {
         alloc_size = nlk->max_recvmsg_len;
         skb = alloc_skb(alloc_size,
                 (GFP_KERNEL & ~__GFP_DIRECT_RECLAIM) |
                 __GFP_NOWARN | __GFP_NORETRY);
     }
     if (!skb) {
         alloc_size = alloc_min_size;
         skb = alloc_skb(alloc_size, GFP_KERNEL);
     }
     if (!skb)
         goto errout_skb;
 
     /* Trim skb to allocated size. User is expected to provide buffer as
      * large as max(min_dump_alloc, 16KiB (mac_recvmsg_len capped at
      * netlink_recvmsg())). dump will pack as many smaller messages as
      * could fit within the allocated skb. skb is typically allocated
      * with larger space than required (could be as much as near 2x the
      * requested size with align to next power of 2 approach). Allowing
      * dump to use the excess space makes it difficult for a user to have a
      * reasonable static buffer based on the expected largest dump of a
      * single netdev. The outcome is MSG_TRUNC error.
      */
     skb_reserve(skb, skb_tailroom(skb) - alloc_size);
 
     /* Make sure malicious BPF programs can not read unitialized memory
      * from skb->head -> skb->data
      */
     skb_reset_network_header(skb);
     skb_reset_mac_header(skb);
 
     netlink_skb_set_owner_r(skb, sk);
 
     if (nlk->dump_done_errno > 0) {
         cb->extack = &extack;
         nlk->dump_done_errno = cb->dump(skb, cb);
         cb->extack = NULL;
     }
 
     if (nlk->dump_done_errno > 0 ||
         skb_tailroom(skb) < nlmsg_total_size(sizeof(nlk->dump_done_errno))) {
         mutex_unlock(nlk->cb_mutex);
 
         if (sk_filter(sk, skb))
             kfree_skb(skb);
         else
             __netlink_sendskb(sk, skb);
         return 0;
     }
 
     if (netlink_dump_done(nlk, skb, cb, &extack))
         goto errout_skb;
 
 #ifdef CONFIG_COMPAT_NETLINK_MESSAGES
     /* frag_list skb's data is used for compat tasks
      * and the regular skb's data for normal (non-compat) tasks.
      * See netlink_recvmsg().
      */
     if (unlikely(skb_shinfo(skb)->frag_list)) {
         if (netlink_dump_done(nlk, skb_shinfo(skb)->frag_list, cb, &extack))
             goto errout_skb;
     }
 #endif
 
     if (sk_filter(sk, skb))
         kfree_skb(skb);
     else
         __netlink_sendskb(sk, skb);
 
     if (cb->done)
         cb->done(cb);
 
     nlk->cb_running = false;
     module = cb->module;
     skb = cb->skb;
     mutex_unlock(nlk->cb_mutex);
     module_put(module);
     consume_skb(skb);
     return 0;
 
 errout_skb:
     mutex_unlock(nlk->cb_mutex);
     kfree_skb(skb);
     return err;
 }
 
 int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
              const struct nlmsghdr *nlh,
              struct netlink_dump_control *control)
 {
     struct netlink_sock *nlk, *nlk2;
     struct netlink_callback *cb;
     struct sock *sk;
     int ret;
 
     refcount_inc(&skb->users);
 
     sk = netlink_lookup(sock_net(ssk), ssk->sk_protocol, NETLINK_CB(skb).portid);
     if (sk == NULL) {
         ret = -ECONNREFUSED;
         goto error_free;
     }
 
     nlk = nlk_sk(sk);
     mutex_lock(nlk->cb_mutex);
     /* A dump is in progress... */
     if (nlk->cb_running) {
         ret = -EBUSY;
         goto error_unlock;
     }
     /* add reference of module which cb->dump belongs to */
     if (!try_module_get(control->module)) {
         ret = -EPROTONOSUPPORT;
         goto error_unlock;
     }
 
     cb = &nlk->cb;
     memset(cb, 0, sizeof(*cb));
     cb->dump = control->dump;
     cb->done = control->done;
     cb->nlh = nlh;
     cb->data = control->data;
     cb->module = control->module;
     cb->min_dump_alloc = control->min_dump_alloc;
     cb->skb = skb;
 
     nlk2 = nlk_sk(NETLINK_CB(skb).sk);
     cb->strict_check = !!(nlk2->flags & NETLINK_F_STRICT_CHK);
 
     if (control->start) {
         ret = control->start(cb);
         if (ret)
             goto error_put;
     }
 
     nlk->cb_running = true;
     nlk->dump_done_errno = INT_MAX;
 
     mutex_unlock(nlk->cb_mutex);
 
     ret = netlink_dump(sk);
 
     sock_put(sk);
 
     if (ret)
         return ret;
 
     /* We successfully started a dump, by returning -EINTR we
      * signal not to send ACK even if it was requested.
      */
     return -EINTR;
 
 error_put:
     module_put(control->module);
 error_unlock:
     sock_put(sk);
     mutex_unlock(nlk->cb_mutex);
 error_free:
     kfree_skb(skb);
     return ret;
 }
 EXPORT_SYMBOL(__netlink_dump_start);
 
 void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
          const struct netlink_ext_ack *extack)
 {
     struct sk_buff *skb;
     struct nlmsghdr *rep;
     struct nlmsgerr *errmsg;
     size_t payload = sizeof(*errmsg);
     size_t tlvlen = 0;
     struct netlink_sock *nlk = nlk_sk(NETLINK_CB(in_skb).sk);
     unsigned int flags = 0;
     bool nlk_has_extack = nlk->flags & NETLINK_F_EXT_ACK;
 
     /* Error messages get the original request appened, unless the user
      * requests to cap the error message, and get extra error data if
      * requested.
      */
     if (nlk_has_extack && extack && extack->_msg)
         tlvlen += nla_total_size(strlen(extack->_msg) + 1);
 
     if (err && !(nlk->flags & NETLINK_F_CAP_ACK))
         payload += nlmsg_len(nlh);
     else
         flags |= NLM_F_CAPPED;
     if (err && nlk_has_extack && extack && extack->bad_attr)
         tlvlen += nla_total_size(sizeof(u32));
     if (nlk_has_extack && extack && extack->cookie_len)
         tlvlen += nla_total_size(extack->cookie_len);
     if (err && nlk_has_extack && extack && extack->policy)
         tlvlen += netlink_policy_dump_attr_size_estimate(extack->policy);
 
     if (tlvlen)
         flags |= NLM_F_ACK_TLVS;
 
     skb = nlmsg_new(payload + tlvlen, GFP_KERNEL);
     if (!skb) {
         NETLINK_CB(in_skb).sk->sk_err = ENOBUFS;
         sk_error_report(NETLINK_CB(in_skb).sk);
         return;
     }
 
     rep = __nlmsg_put(skb, NETLINK_CB(in_skb).portid, nlh->nlmsg_seq,
               NLMSG_ERROR, payload, flags);
     errmsg = nlmsg_data(rep);
     errmsg->error = err;
     memcpy(&errmsg->msg, nlh, payload > sizeof(*errmsg) ? nlh->nlmsg_len : sizeof(*nlh));
 
     if (nlk_has_extack && extack) {
         if (extack->_msg) {
             WARN_ON(nla_put_string(skb, NLMSGERR_ATTR_MSG,
                            extack->_msg));
         }
         if (err && extack->bad_attr &&
             !WARN_ON((u8 *)extack->bad_attr < in_skb->data ||
                  (u8 *)extack->bad_attr >= in_skb->data +
                                in_skb->len))
             WARN_ON(nla_put_u32(skb, NLMSGERR_ATTR_OFFS,
                         (u8 *)extack->bad_attr -
                         (u8 *)nlh));
         if (extack->cookie_len)
             WARN_ON(nla_put(skb, NLMSGERR_ATTR_COOKIE,
                     extack->cookie_len, extack->cookie));
         if (extack->policy)
             netlink_policy_dump_write_attr(skb, extack->policy,
                                NLMSGERR_ATTR_POLICY);
     }
 
     nlmsg_end(skb, rep);
 
     nlmsg_unicast(in_skb->sk, skb, NETLINK_CB(in_skb).portid);
 }
 EXPORT_SYMBOL(netlink_ack);
 
 int netlink_rcv_skb(struct sk_buff *skb, int (*cb)(struct sk_buff *,
                            struct nlmsghdr *,
                            struct netlink_ext_ack *))
 {
     struct netlink_ext_ack extack;
     struct nlmsghdr *nlh;
     int err;
 
     while (skb->len >= nlmsg_total_size(0)) {
         int msglen;
 
         memset(&extack, 0, sizeof(extack));
         nlh = nlmsg_hdr(skb);
         err = 0;
 
         if (nlh->nlmsg_len < NLMSG_HDRLEN || skb->len < nlh->nlmsg_len)
             return 0;
 
         /* Only requests are handled by the kernel */
         if (!(nlh->nlmsg_flags & NLM_F_REQUEST))
             goto ack;
 
         /* Skip control messages */
         if (nlh->nlmsg_type < NLMSG_MIN_TYPE)
             goto ack;
 
         err = cb(skb, nlh, &extack);
         if (err == -EINTR)
             goto skip;
 
 ack:
         if (nlh->nlmsg_flags & NLM_F_ACK || err)
             netlink_ack(skb, nlh, err, &extack);
 
 skip:
         msglen = NLMSG_ALIGN(nlh->nlmsg_len);
         if (msglen > skb->len)
             msglen = skb->len;
         skb_pull(skb, msglen);
     }
 
     return 0;
 }
 EXPORT_SYMBOL(netlink_rcv_skb);
 
 /**
  * nlmsg_notify - send a notification netlink message
  * @sk: netlink socket to use
  * @skb: notification message
  * @portid: destination netlink portid for reports or 0
  * @group: destination multicast group or 0
  * @report: 1 to report back, 0 to disable
  * @flags: allocation flags
  */
 int nlmsg_notify(struct sock *sk, struct sk_buff *skb, u32 portid,
          unsigned int group, int report, gfp_t flags)
 {
     int err = 0;
 
     if (group) {
         int exclude_portid = 0;
 
         if (report) {
             refcount_inc(&skb->users);
             exclude_portid = portid;
         }
 
         /* errors reported via destination sk->sk_err, but propagate
          * delivery errors if NETLINK_BROADCAST_ERROR flag is set */
         err = nlmsg_multicast(sk, skb, exclude_portid, group, flags);
         if (err == -ESRCH)
             err = 0;
     }
 
     if (report) {
         int err2;
 
         err2 = nlmsg_unicast(sk, skb, portid);
         if (!err)
             err = err2;
     }
 
     return err;
 }
 EXPORT_SYMBOL(nlmsg_notify);
 
 #ifdef CONFIG_PROC_FS
 struct nl_seq_iter {
     struct seq_net_private p;
     struct rhashtable_iter hti;
     int link;
 };
 
 static void netlink_walk_start(struct nl_seq_iter *iter)
 {
     rhashtable_walk_enter(&nl_table[iter->link].hash, &iter->hti);
     rhashtable_walk_start(&iter->hti);
 }
 
 static void netlink_walk_stop(struct nl_seq_iter *iter)
 {
     rhashtable_walk_stop(&iter->hti);
     rhashtable_walk_exit(&iter->hti);
 }
 
 static void *__netlink_seq_next(struct seq_file *seq)
 {
     struct nl_seq_iter *iter = seq->private;
     struct netlink_sock *nlk;
 
     do {
         for (;;) {
             nlk = rhashtable_walk_next(&iter->hti);
 
             if (IS_ERR(nlk)) {
                 if (PTR_ERR(nlk) == -EAGAIN)
                     continue;
 
                 return nlk;
             }
 
             if (nlk)
                 break;
 
             netlink_walk_stop(iter);
             if (++iter->link >= MAX_LINKS)
                 return NULL;
 
             netlink_walk_start(iter);
         }
     } while (sock_net(&nlk->sk) != seq_file_net(seq));
 
     return nlk;
 }
 
 static void *netlink_seq_start(struct seq_file *seq, loff_t *posp)
     __acquires(RCU)
 {
     struct nl_seq_iter *iter = seq->private;
     void *obj = SEQ_START_TOKEN;
     loff_t pos;
 
     iter->link = 0;
 
     netlink_walk_start(iter);
 
     for (pos = *posp; pos && obj && !IS_ERR(obj); pos--)
         obj = __netlink_seq_next(seq);
 
     return obj;
 }
 
 static void *netlink_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 {
     ++*pos;
     return __netlink_seq_next(seq);
 }
 
 static void netlink_native_seq_stop(struct seq_file *seq, void *v)
 {
     struct nl_seq_iter *iter = seq->private;
 
     if (iter->link >= MAX_LINKS)
         return;
 
     netlink_walk_stop(iter);
 }
 
 
 static int netlink_native_seq_show(struct seq_file *seq, void *v)
 {
     if (v == SEQ_START_TOKEN) {
         seq_puts(seq,
              "sk               Eth Pid        Groups   "
              "Rmem     Wmem     Dump  Locks    Drops    Inode\n");
     } else {
         struct sock *s = v;
         struct netlink_sock *nlk = nlk_sk(s);
 
         seq_printf(seq, "%pK %-3d %-10u %08x %-8d %-8d %-5d %-8d %-8u %-8lu\n",
                s,
                s->sk_protocol,
                nlk->portid,
                nlk->groups ? (u32)nlk->groups[0] : 0,
                sk_rmem_alloc_get(s),
                sk_wmem_alloc_get(s),
                nlk->cb_running,
                refcount_read(&s->sk_refcnt),
                atomic_read(&s->sk_drops),
                sock_i_ino(s)
             );
 
     }
     return 0;
 }
 
 #ifdef CONFIG_BPF_SYSCALL
 struct bpf_iter__netlink {
     __bpf_md_ptr(struct bpf_iter_meta *, meta);
     __bpf_md_ptr(struct netlink_sock *, sk);
 };
 
 DEFINE_BPF_ITER_FUNC(netlink, struct bpf_iter_meta *meta, struct netlink_sock *sk)
 
 static int netlink_prog_seq_show(struct bpf_prog *prog,
                   struct bpf_iter_meta *meta,
                   void *v)
 {
     struct bpf_iter__netlink ctx;
 
     meta->seq_num--;  /* skip SEQ_START_TOKEN */
     ctx.meta = meta;
     ctx.sk = nlk_sk((struct sock *)v);
     return bpf_iter_run_prog(prog, &ctx);
 }
 
 static int netlink_seq_show(struct seq_file *seq, void *v)
 {
     struct bpf_iter_meta meta;
     struct bpf_prog *prog;
 
     meta.seq = seq;
     prog = bpf_iter_get_info(&meta, false);
     if (!prog)
         return netlink_native_seq_show(seq, v);
 
     if (v != SEQ_START_TOKEN)
         return netlink_prog_seq_show(prog, &meta, v);
 
     return 0;
 }
 
 static void netlink_seq_stop(struct seq_file *seq, void *v)
 {
     struct bpf_iter_meta meta;
     struct bpf_prog *prog;
 
     if (!v) {
         meta.seq = seq;
         prog = bpf_iter_get_info(&meta, true);
         if (prog)
             (void)netlink_prog_seq_show(prog, &meta, v);
     }
 
     netlink_native_seq_stop(seq, v);
 }
 #else
 static int netlink_seq_show(struct seq_file *seq, void *v)
 {
     return netlink_native_seq_show(seq, v);
 }
 
 static void netlink_seq_stop(struct seq_file *seq, void *v)
 {
     netlink_native_seq_stop(seq, v);
 }
 #endif
 
 static const struct seq_operations netlink_seq_ops = {
     .start  = netlink_seq_start,
     .next   = netlink_seq_next,
     .stop   = netlink_seq_stop,
     .show   = netlink_seq_show,
 };
 #endif
 
 int netlink_register_notifier(struct notifier_block *nb)
 {
     return blocking_notifier_chain_register(&netlink_chain, nb);
 }
 EXPORT_SYMBOL(netlink_register_notifier);
 
 int netlink_unregister_notifier(struct notifier_block *nb)
 {
     return blocking_notifier_chain_unregister(&netlink_chain, nb);
 }
 EXPORT_SYMBOL(netlink_unregister_notifier);
 
 static const struct proto_ops netlink_ops = {
     .family =   PF_NETLINK,
     .owner =    THIS_MODULE,
     .release =  netlink_release,
     .bind =     netlink_bind,
     .connect =  netlink_connect,
     .socketpair =   sock_no_socketpair,
     .accept =   sock_no_accept,
     .getname =  netlink_getname,
     .poll =     datagram_poll,
     .ioctl =    netlink_ioctl,
     .listen =   sock_no_listen,
     .shutdown = sock_no_shutdown,
     .setsockopt =   netlink_setsockopt,
     .getsockopt =   netlink_getsockopt,
     .sendmsg =  netlink_sendmsg,
     .recvmsg =  netlink_recvmsg,
     .mmap =     sock_no_mmap,
     .sendpage = sock_no_sendpage,
 };
 
 static const struct net_proto_family netlink_family_ops = {
     .family = PF_NETLINK,
     .create = netlink_create,
     .owner  = THIS_MODULE,  /* for consistency 8) */
 };
 
 static int __net_init netlink_net_init(struct net *net)
 {
 #ifdef CONFIG_PROC_FS
     if (!proc_create_net("netlink", 0, net->proc_net, &netlink_seq_ops,
             sizeof(struct nl_seq_iter)))
         return -ENOMEM;
 #endif
     return 0;
 }
 
 static void __net_exit netlink_net_exit(struct net *net)
 {
 #ifdef CONFIG_PROC_FS
     remove_proc_entry("netlink", net->proc_net);
 #endif
 }
 
 static void __init netlink_add_usersock_entry(void)
 {
     struct listeners *listeners;
     int groups = 32;
 
     listeners = kzalloc(sizeof(*listeners) + NLGRPSZ(groups), GFP_KERNEL);
     if (!listeners)
         panic("netlink_add_usersock_entry: Cannot allocate listeners\n");
 
     netlink_table_grab();
 
     nl_table[NETLINK_USERSOCK].groups = groups;
     rcu_assign_pointer(nl_table[NETLINK_USERSOCK].listeners, listeners);
     nl_table[NETLINK_USERSOCK].module = THIS_MODULE;
     nl_table[NETLINK_USERSOCK].registered = 1;
     nl_table[NETLINK_USERSOCK].flags = NL_CFG_F_NONROOT_SEND;
 
     netlink_table_ungrab();
 }
 
 static struct pernet_operations __net_initdata netlink_net_ops = {
     .init = netlink_net_init,
     .exit = netlink_net_exit,
 };
 
 static inline u32 netlink_hash(const void *data, u32 len, u32 seed)
 {
     const struct netlink_sock *nlk = data;
     struct netlink_compare_arg arg;
 
     netlink_compare_arg_init(&arg, sock_net(&nlk->sk), nlk->portid);
     return jhash2((u32 *)&arg, netlink_compare_arg_len / sizeof(u32), seed);
 }
 
 static const struct rhashtable_params netlink_rhashtable_params = {
     .head_offset = offsetof(struct netlink_sock, node),
     .key_len = netlink_compare_arg_len,
     .obj_hashfn = netlink_hash,
     .obj_cmpfn = netlink_compare,
     .automatic_shrinking = true,
 };
 
 #if defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_PROC_FS)
 BTF_ID_LIST(btf_netlink_sock_id)
 BTF_ID(struct, netlink_sock)
 
 static const struct bpf_iter_seq_info netlink_seq_info = {
     .seq_ops        = &netlink_seq_ops,
     .init_seq_private   = bpf_iter_init_seq_net,
     .fini_seq_private   = bpf_iter_fini_seq_net,
     .seq_priv_size      = sizeof(struct nl_seq_iter),
 };
 
 static struct bpf_iter_reg netlink_reg_info = {
     .target         = "netlink",
     .ctx_arg_info_size  = 1,
     .ctx_arg_info       = {
         { offsetof(struct bpf_iter__netlink, sk),
           PTR_TO_BTF_ID_OR_NULL },
     },
     .seq_info       = &netlink_seq_info,
 };
 
 static int __init bpf_iter_register(void)
 {
     netlink_reg_info.ctx_arg_info[0].btf_id = *btf_netlink_sock_id;
     return bpf_iter_reg_target(&netlink_reg_info);
 }
 #endif
 
 static int __init netlink_proto_init(void)
 {
     int i;
     int err = proto_register(&netlink_proto, 0);
 
     if (err != 0)
         goto out;
 
 #if defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_PROC_FS)
     err = bpf_iter_register();
     if (err)
         goto out;
 #endif
 
     BUILD_BUG_ON(sizeof(struct netlink_skb_parms) > sizeof_field(struct sk_buff, cb));
 
     nl_table = kcalloc(MAX_LINKS, sizeof(*nl_table), GFP_KERNEL);
     if (!nl_table)
         goto panic;
 
     for (i = 0; i < MAX_LINKS; i++) {
         if (rhashtable_init(&nl_table[i].hash,
                     &netlink_rhashtable_params) < 0) {
             while (--i > 0)
                 rhashtable_destroy(&nl_table[i].hash);
             kfree(nl_table);
             goto panic;
         }
     }
 
     netlink_add_usersock_entry();
 
     sock_register(&netlink_family_ops);
     register_pernet_subsys(&netlink_net_ops);
     register_pernet_subsys(&netlink_tap_net_ops);
     /* The netlink device handler may be needed early. */
     rtnetlink_init();
 out:
     return err;
 panic:
     panic("netlink_init: Cannot allocate nl_table\n");
 }
 
 core_initcall(netlink_proto_init);