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 // SPDX-License-Identifier: GPL-2.0
 /*
  * linux/ipc/util.c
  * Copyright (C) 1992 Krishna Balasubramanian
  *
  * Sep 1997 - Call suser() last after "normal" permission checks so we
  *            get BSD style process accounting right.
  *            Occurs in several places in the IPC code.
  *            Chris Evans, <chris@ferret.lmh.ox.ac.uk>
  * Nov 1999 - ipc helper functions, unified SMP locking
  *        Manfred Spraul <manfred@colorfullife.com>
  * Oct 2002 - One lock per IPC id. RCU ipc_free for lock-free grow_ary().
  *            Mingming Cao <cmm@us.ibm.com>
  * Mar 2006 - support for audit of ipc object properties
  *            Dustin Kirkland <dustin.kirkland@us.ibm.com>
  * Jun 2006 - namespaces ssupport
  *            OpenVZ, SWsoft Inc.
  *            Pavel Emelianov <xemul@openvz.org>
  *
  * General sysv ipc locking scheme:
  *  rcu_read_lock()
  *          obtain the ipc object (kern_ipc_perm) by looking up the id in an idr
  *      tree.
  *      - perform initial checks (capabilities, auditing and permission,
  *        etc).
  *      - perform read-only operations, such as INFO command, that
  *        do not demand atomicity
  *        acquire the ipc lock (kern_ipc_perm.lock) through
  *        ipc_lock_object()
  *      - perform read-only operations that demand atomicity,
  *        such as STAT command.
  *      - perform data updates, such as SET, RMID commands and
  *        mechanism-specific operations (semop/semtimedop,
  *        msgsnd/msgrcv, shmat/shmdt).
  *      drop the ipc lock, through ipc_unlock_object().
  *  rcu_read_unlock()
  *
  *  The ids->rwsem must be taken when:
  *  - creating, removing and iterating the existing entries in ipc
  *    identifier sets.
  *  - iterating through files under /proc/sysvipc/
  *
  *  Note that sems have a special fast path that avoids kern_ipc_perm.lock -
  *  see sem_lock().
  */
 
 #include <linux/mm.h>
 #include <linux/shm.h>
 #include <linux/init.h>
 #include <linux/msg.h>
 #include <linux/vmalloc.h>
 #include <linux/slab.h>
 #include <linux/notifier.h>
 #include <linux/capability.h>
 #include <linux/highuid.h>
 #include <linux/security.h>
 #include <linux/rcupdate.h>
 #include <linux/workqueue.h>
 #include <linux/seq_file.h>
 #include <linux/proc_fs.h>
 #include <linux/audit.h>
 #include <linux/nsproxy.h>
 #include <linux/rwsem.h>
 #include <linux/memory.h>
 #include <linux/ipc_namespace.h>
 #include <linux/rhashtable.h>
 #include <linux/log2.h>
 
 #include <asm/unistd.h>
 
 #include "util.h"
 
 struct ipc_proc_iface {
     const char *path;
     const char *header;
     int ids;
     int (*show)(struct seq_file *, void *);
 };
 
 /**
  * ipc_init - initialise ipc subsystem
  *
  * The various sysv ipc resources (semaphores, messages and shared
  * memory) are initialised.
  *
  * A callback routine is registered into the memory hotplug notifier
  * chain: since msgmni scales to lowmem this callback routine will be
  * called upon successful memory add / remove to recompute msmgni.
  */
 static int __init ipc_init(void)
 {
     proc_mkdir("sysvipc", NULL);
     sem_init();
     msg_init();
     shm_init();
 
     return 0;
 }
 device_initcall(ipc_init);
 
 static const struct rhashtable_params ipc_kht_params = {
     .head_offset        = offsetof(struct kern_ipc_perm, khtnode),
     .key_offset     = offsetof(struct kern_ipc_perm, key),
     .key_len        = sizeof_field(struct kern_ipc_perm, key),
     .automatic_shrinking    = true,
 };
 
 /**
  * ipc_init_ids - initialise ipc identifiers
  * @ids: ipc identifier set
  *
  * Set up the sequence range to use for the ipc identifier range (limited
  * below ipc_mni) then initialise the keys hashtable and ids idr.
  */
 void ipc_init_ids(struct ipc_ids *ids)
 {
     ids->in_use = 0;
     ids->seq = 0;
     init_rwsem(&ids->rwsem);
     rhashtable_init(&ids->key_ht, &ipc_kht_params);
     idr_init(&ids->ipcs_idr);
     ids->max_idx = -1;
     ids->last_idx = -1;
 #ifdef CONFIG_CHECKPOINT_RESTORE
     ids->next_id = -1;
 #endif
 }
 
 #ifdef CONFIG_PROC_FS
 static const struct proc_ops sysvipc_proc_ops;
 /**
  * ipc_init_proc_interface -  create a proc interface for sysipc types using a seq_file interface.
  * @path: Path in procfs
  * @header: Banner to be printed at the beginning of the file.
  * @ids: ipc id table to iterate.
  * @show: show routine.
  */
 void __init ipc_init_proc_interface(const char *path, const char *header,
         int ids, int (*show)(struct seq_file *, void *))
 {
     struct proc_dir_entry *pde;
     struct ipc_proc_iface *iface;
 
     iface = kmalloc(sizeof(*iface), GFP_KERNEL);
     if (!iface)
         return;
     iface->path = path;
     iface->header   = header;
     iface->ids  = ids;
     iface->show = show;
 
     pde = proc_create_data(path,
                    S_IRUGO,        /* world readable */
                    NULL,           /* parent dir */
                    &sysvipc_proc_ops,
                    iface);
     if (!pde)
         kfree(iface);
 }
 #endif
 
 /**
  * ipc_findkey  - find a key in an ipc identifier set
  * @ids: ipc identifier set
  * @key: key to find
  *
  * Returns the locked pointer to the ipc structure if found or NULL
  * otherwise. If key is found ipc points to the owning ipc structure
  *
  * Called with writer ipc_ids.rwsem held.
  */
 static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
 {
     struct kern_ipc_perm *ipcp;
 
     ipcp = rhashtable_lookup_fast(&ids->key_ht, &key,
                           ipc_kht_params);
     if (!ipcp)
         return NULL;
 
     rcu_read_lock();
     ipc_lock_object(ipcp);
     return ipcp;
 }
 
 /*
  * Insert new IPC object into idr tree, and set sequence number and id
  * in the correct order.
  * Especially:
  * - the sequence number must be set before inserting the object into the idr,
  *   because the sequence number is accessed without a lock.
  * - the id can/must be set after inserting the object into the idr.
  *   All accesses must be done after getting kern_ipc_perm.lock.
  *
  * The caller must own kern_ipc_perm.lock.of the new object.
  * On error, the function returns a (negative) error code.
  *
  * To conserve sequence number space, especially with extended ipc_mni,
  * the sequence number is incremented only when the returned ID is less than
  * the last one.
  */
 static inline int ipc_idr_alloc(struct ipc_ids *ids, struct kern_ipc_perm *new)
 {
     int idx, next_id = -1;
 
 #ifdef CONFIG_CHECKPOINT_RESTORE
     next_id = ids->next_id;
     ids->next_id = -1;
 #endif
 
     /*
      * As soon as a new object is inserted into the idr,
      * ipc_obtain_object_idr() or ipc_obtain_object_check() can find it,
      * and the lockless preparations for ipc operations can start.
      * This means especially: permission checks, audit calls, allocation
      * of undo structures, ...
      *
      * Thus the object must be fully initialized, and if something fails,
      * then the full tear-down sequence must be followed.
      * (i.e.: set new->deleted, reduce refcount, call_rcu())
      */
 
     if (next_id < 0) { /* !CHECKPOINT_RESTORE or next_id is unset */
         int max_idx;
 
         max_idx = max(ids->in_use*3/2, ipc_min_cycle);
         max_idx = min(max_idx, ipc_mni);
 
         /* allocate the idx, with a NULL struct kern_ipc_perm */
         idx = idr_alloc_cyclic(&ids->ipcs_idr, NULL, 0, max_idx,
                     GFP_NOWAIT);
 
         if (idx >= 0) {
             /*
              * idx got allocated successfully.
              * Now calculate the sequence number and set the
              * pointer for real.
              */
             if (idx <= ids->last_idx) {
                 ids->seq++;
                 if (ids->seq >= ipcid_seq_max())
                     ids->seq = 0;
             }
             ids->last_idx = idx;
 
             new->seq = ids->seq;
             /* no need for smp_wmb(), this is done
              * inside idr_replace, as part of
              * rcu_assign_pointer
              */
             idr_replace(&ids->ipcs_idr, new, idx);
         }
     } else {
         new->seq = ipcid_to_seqx(next_id);
         idx = idr_alloc(&ids->ipcs_idr, new, ipcid_to_idx(next_id),
                 0, GFP_NOWAIT);
     }
     if (idx >= 0)
         new->id = (new->seq << ipcmni_seq_shift()) + idx;
     return idx;
 }
 
 /**
  * ipc_addid - add an ipc identifier
  * @ids: ipc identifier set
  * @new: new ipc permission set
  * @limit: limit for the number of used ids
  *
  * Add an entry 'new' to the ipc ids idr. The permissions object is
  * initialised and the first free entry is set up and the index assigned
  * is returned. The 'new' entry is returned in a locked state on success.
  *
  * On failure the entry is not locked and a negative err-code is returned.
  * The caller must use ipc_rcu_putref() to free the identifier.
  *
  * Called with writer ipc_ids.rwsem held.
  */
 int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int limit)
 {
     kuid_t euid;
     kgid_t egid;
     int idx, err;
 
     /* 1) Initialize the refcount so that ipc_rcu_putref works */
     refcount_set(&new->refcount, 1);
 
     if (limit > ipc_mni)
         limit = ipc_mni;
 
     if (ids->in_use >= limit)
         return -ENOSPC;
 
     idr_preload(GFP_KERNEL);
 
     spin_lock_init(&new->lock);
     rcu_read_lock();
     spin_lock(&new->lock);
 
     current_euid_egid(&euid, &egid);
     new->cuid = new->uid = euid;
     new->gid = new->cgid = egid;
 
     new->deleted = false;
 
     idx = ipc_idr_alloc(ids, new);
     idr_preload_end();
 
     if (idx >= 0 && new->key != IPC_PRIVATE) {
         err = rhashtable_insert_fast(&ids->key_ht, &new->khtnode,
                          ipc_kht_params);
         if (err < 0) {
             idr_remove(&ids->ipcs_idr, idx);
             idx = err;
         }
     }
     if (idx < 0) {
         new->deleted = true;
         spin_unlock(&new->lock);
         rcu_read_unlock();
         return idx;
     }
 
     ids->in_use++;
     if (idx > ids->max_idx)
         ids->max_idx = idx;
     return idx;
 }
 
 /**
  * ipcget_new - create a new ipc object
  * @ns: ipc namespace
  * @ids: ipc identifier set
  * @ops: the actual creation routine to call
  * @params: its parameters
  *
  * This routine is called by sys_msgget, sys_semget() and sys_shmget()
  * when the key is IPC_PRIVATE.
  */
 static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
         const struct ipc_ops *ops, struct ipc_params *params)
 {
     int err;
 
     down_write(&ids->rwsem);
     err = ops->getnew(ns, params);
     up_write(&ids->rwsem);
     return err;
 }
 
 /**
  * ipc_check_perms - check security and permissions for an ipc object
  * @ns: ipc namespace
  * @ipcp: ipc permission set
  * @ops: the actual security routine to call
  * @params: its parameters
  *
  * This routine is called by sys_msgget(), sys_semget() and sys_shmget()
  * when the key is not IPC_PRIVATE and that key already exists in the
  * ds IDR.
  *
  * On success, the ipc id is returned.
  *
  * It is called with ipc_ids.rwsem and ipcp->lock held.
  */
 static int ipc_check_perms(struct ipc_namespace *ns,
                struct kern_ipc_perm *ipcp,
                const struct ipc_ops *ops,
                struct ipc_params *params)
 {
     int err;
 
     if (ipcperms(ns, ipcp, params->flg))
         err = -EACCES;
     else {
         err = ops->associate(ipcp, params->flg);
         if (!err)
             err = ipcp->id;
     }
 
     return err;
 }
 
 /**
  * ipcget_public - get an ipc object or create a new one
  * @ns: ipc namespace
  * @ids: ipc identifier set
  * @ops: the actual creation routine to call
  * @params: its parameters
  *
  * This routine is called by sys_msgget, sys_semget() and sys_shmget()
  * when the key is not IPC_PRIVATE.
  * It adds a new entry if the key is not found and does some permission
  * / security checkings if the key is found.
  *
  * On success, the ipc id is returned.
  */
 static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
         const struct ipc_ops *ops, struct ipc_params *params)
 {
     struct kern_ipc_perm *ipcp;
     int flg = params->flg;
     int err;
 
     /*
      * Take the lock as a writer since we are potentially going to add
      * a new entry + read locks are not "upgradable"
      */
     down_write(&ids->rwsem);
     ipcp = ipc_findkey(ids, params->key);
     if (ipcp == NULL) {
         /* key not used */
         if (!(flg & IPC_CREAT))
             err = -ENOENT;
         else
             err = ops->getnew(ns, params);
     } else {
         /* ipc object has been locked by ipc_findkey() */
 
         if (flg & IPC_CREAT && flg & IPC_EXCL)
             err = -EEXIST;
         else {
             err = 0;
             if (ops->more_checks)
                 err = ops->more_checks(ipcp, params);
             if (!err)
                 /*
                  * ipc_check_perms returns the IPC id on
                  * success
                  */
                 err = ipc_check_perms(ns, ipcp, ops, params);
         }
         ipc_unlock(ipcp);
     }
     up_write(&ids->rwsem);
 
     return err;
 }
 
 /**
  * ipc_kht_remove - remove an ipc from the key hashtable
  * @ids: ipc identifier set
  * @ipcp: ipc perm structure containing the key to remove
  *
  * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
  * before this function is called, and remain locked on the exit.
  */
 static void ipc_kht_remove(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
 {
     if (ipcp->key != IPC_PRIVATE)
         WARN_ON_ONCE(rhashtable_remove_fast(&ids->key_ht, &ipcp->khtnode,
                        ipc_kht_params));
 }
 
 /**
  * ipc_search_maxidx - search for the highest assigned index
  * @ids: ipc identifier set
  * @limit: known upper limit for highest assigned index
  *
  * The function determines the highest assigned index in @ids. It is intended
  * to be called when ids->max_idx needs to be updated.
  * Updating ids->max_idx is necessary when the current highest index ipc
  * object is deleted.
  * If no ipc object is allocated, then -1 is returned.
  *
  * ipc_ids.rwsem needs to be held by the caller.
  */
 static int ipc_search_maxidx(struct ipc_ids *ids, int limit)
 {
     int tmpidx;
     int i;
     int retval;
 
     i = ilog2(limit+1);
 
     retval = 0;
     for (; i >= 0; i--) {
         tmpidx = retval | (1<<i);
         /*
          * "0" is a possible index value, thus search using
          * e.g. 15,7,3,1,0 instead of 16,8,4,2,1.
          */
         tmpidx = tmpidx-1;
         if (idr_get_next(&ids->ipcs_idr, &tmpidx))
             retval |= (1<<i);
     }
     return retval - 1;
 }
 
 /**
  * ipc_rmid - remove an ipc identifier
  * @ids: ipc identifier set
  * @ipcp: ipc perm structure containing the identifier to remove
  *
  * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
  * before this function is called, and remain locked on the exit.
  */
 void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
 {
     int idx = ipcid_to_idx(ipcp->id);
 
     WARN_ON_ONCE(idr_remove(&ids->ipcs_idr, idx) != ipcp);
     ipc_kht_remove(ids, ipcp);
     ids->in_use--;
     ipcp->deleted = true;
 
     if (unlikely(idx == ids->max_idx)) {
         idx = ids->max_idx-1;
         if (idx >= 0)
             idx = ipc_search_maxidx(ids, idx);
         ids->max_idx = idx;
     }
 }
 
 /**
  * ipc_set_key_private - switch the key of an existing ipc to IPC_PRIVATE
  * @ids: ipc identifier set
  * @ipcp: ipc perm structure containing the key to modify
  *
  * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
  * before this function is called, and remain locked on the exit.
  */
 void ipc_set_key_private(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
 {
     ipc_kht_remove(ids, ipcp);
     ipcp->key = IPC_PRIVATE;
 }
 
 bool ipc_rcu_getref(struct kern_ipc_perm *ptr)
 {
     return refcount_inc_not_zero(&ptr->refcount);
 }
 
 void ipc_rcu_putref(struct kern_ipc_perm *ptr,
             void (*func)(struct rcu_head *head))
 {
     if (!refcount_dec_and_test(&ptr->refcount))
         return;
 
     call_rcu(&ptr->rcu, func);
 }
 
 /**
  * ipcperms - check ipc permissions
  * @ns: ipc namespace
  * @ipcp: ipc permission set
  * @flag: desired permission set
  *
  * Check user, group, other permissions for access
  * to ipc resources. return 0 if allowed
  *
  * @flag will most probably be 0 or ``S_...UGO`` from <linux/stat.h>
  */
 int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flag)
 {
     kuid_t euid = current_euid();
     int requested_mode, granted_mode;
 
     audit_ipc_obj(ipcp);
     requested_mode = (flag >> 6) | (flag >> 3) | flag;
     granted_mode = ipcp->mode;
     if (uid_eq(euid, ipcp->cuid) ||
         uid_eq(euid, ipcp->uid))
         granted_mode >>= 6;
     else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
         granted_mode >>= 3;
     /* is there some bit set in requested_mode but not in granted_mode? */
     if ((requested_mode & ~granted_mode & 0007) &&
         !ns_capable(ns->user_ns, CAP_IPC_OWNER))
         return -1;
 
     return security_ipc_permission(ipcp, flag);
 }
 
 /*
  * Functions to convert between the kern_ipc_perm structure and the
  * old/new ipc_perm structures
  */
 
 /**
  * kernel_to_ipc64_perm - convert kernel ipc permissions to user
  * @in: kernel permissions
  * @out: new style ipc permissions
  *
  * Turn the kernel object @in into a set of permissions descriptions
  * for returning to userspace (@out).
  */
 void kernel_to_ipc64_perm(struct kern_ipc_perm *in, struct ipc64_perm *out)
 {
     out->key    = in->key;
     out->uid    = from_kuid_munged(current_user_ns(), in->uid);
     out->gid    = from_kgid_munged(current_user_ns(), in->gid);
     out->cuid   = from_kuid_munged(current_user_ns(), in->cuid);
     out->cgid   = from_kgid_munged(current_user_ns(), in->cgid);
     out->mode   = in->mode;
     out->seq    = in->seq;
 }
 
 /**
  * ipc64_perm_to_ipc_perm - convert new ipc permissions to old
  * @in: new style ipc permissions
  * @out: old style ipc permissions
  *
  * Turn the new style permissions object @in into a compatibility
  * object and store it into the @out pointer.
  */
 void ipc64_perm_to_ipc_perm(struct ipc64_perm *in, struct ipc_perm *out)
 {
     out->key    = in->key;
     SET_UID(out->uid, in->uid);
     SET_GID(out->gid, in->gid);
     SET_UID(out->cuid, in->cuid);
     SET_GID(out->cgid, in->cgid);
     out->mode   = in->mode;
     out->seq    = in->seq;
 }
 
 /**
  * ipc_obtain_object_idr
  * @ids: ipc identifier set
  * @id: ipc id to look for
  *
  * Look for an id in the ipc ids idr and return associated ipc object.
  *
  * Call inside the RCU critical section.
  * The ipc object is *not* locked on exit.
  */
 struct kern_ipc_perm *ipc_obtain_object_idr(struct ipc_ids *ids, int id)
 {
     struct kern_ipc_perm *out;
     int idx = ipcid_to_idx(id);
 
     out = idr_find(&ids->ipcs_idr, idx);
     if (!out)
         return ERR_PTR(-EINVAL);
 
     return out;
 }
 
 /**
  * ipc_obtain_object_check
  * @ids: ipc identifier set
  * @id: ipc id to look for
  *
  * Similar to ipc_obtain_object_idr() but also checks the ipc object
  * sequence number.
  *
  * Call inside the RCU critical section.
  * The ipc object is *not* locked on exit.
  */
 struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id)
 {
     struct kern_ipc_perm *out = ipc_obtain_object_idr(ids, id);
 
     if (IS_ERR(out))
         goto out;
 
     if (ipc_checkid(out, id))
         return ERR_PTR(-EINVAL);
 out:
     return out;
 }
 
 /**
  * ipcget - Common sys_*get() code
  * @ns: namespace
  * @ids: ipc identifier set
  * @ops: operations to be called on ipc object creation, permission checks
  *       and further checks
  * @params: the parameters needed by the previous operations.
  *
  * Common routine called by sys_msgget(), sys_semget() and sys_shmget().
  */
 int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
             const struct ipc_ops *ops, struct ipc_params *params)
 {
     if (params->key == IPC_PRIVATE)
         return ipcget_new(ns, ids, ops, params);
     else
         return ipcget_public(ns, ids, ops, params);
 }
 
 /**
  * ipc_update_perm - update the permissions of an ipc object
  * @in:  the permission given as input.
  * @out: the permission of the ipc to set.
  */
 int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
 {
     kuid_t uid = make_kuid(current_user_ns(), in->uid);
     kgid_t gid = make_kgid(current_user_ns(), in->gid);
     if (!uid_valid(uid) || !gid_valid(gid))
         return -EINVAL;
 
     out->uid = uid;
     out->gid = gid;
     out->mode = (out->mode & ~S_IRWXUGO)
         | (in->mode & S_IRWXUGO);
 
     return 0;
 }
 
 /**
  * ipcctl_obtain_check - retrieve an ipc object and check permissions
  * @ns:  ipc namespace
  * @ids:  the table of ids where to look for the ipc
  * @id:   the id of the ipc to retrieve
  * @cmd:  the cmd to check
  * @perm: the permission to set
  * @extra_perm: one extra permission parameter used by msq
  *
  * This function does some common audit and permissions check for some IPC_XXX
  * cmd and is called from semctl_down, shmctl_down and msgctl_down.
  *
  * It:
  *   - retrieves the ipc object with the given id in the given table.
  *   - performs some audit and permission check, depending on the given cmd
  *   - returns a pointer to the ipc object or otherwise, the corresponding
  *     error.
  *
  * Call holding the both the rwsem and the rcu read lock.
  */
 struct kern_ipc_perm *ipcctl_obtain_check(struct ipc_namespace *ns,
                     struct ipc_ids *ids, int id, int cmd,
                     struct ipc64_perm *perm, int extra_perm)
 {
     kuid_t euid;
     int err = -EPERM;
     struct kern_ipc_perm *ipcp;
 
     ipcp = ipc_obtain_object_check(ids, id);
     if (IS_ERR(ipcp)) {
         err = PTR_ERR(ipcp);
         goto err;
     }
 
     audit_ipc_obj(ipcp);
     if (cmd == IPC_SET)
         audit_ipc_set_perm(extra_perm, perm->uid,
                    perm->gid, perm->mode);
 
     euid = current_euid();
     if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid)  ||
         ns_capable(ns->user_ns, CAP_SYS_ADMIN))
         return ipcp; /* successful lookup */
 err:
     return ERR_PTR(err);
 }
 
 #ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
 
 
 /**
  * ipc_parse_version - ipc call version
  * @cmd: pointer to command
  *
  * Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
  * The @cmd value is turned from an encoding command and version into
  * just the command code.
  */
 int ipc_parse_version(int *cmd)
 {
     if (*cmd & IPC_64) {
         *cmd ^= IPC_64;
         return IPC_64;
     } else {
         return IPC_OLD;
     }
 }
 
 #endif /* CONFIG_ARCH_WANT_IPC_PARSE_VERSION */
 
 #ifdef CONFIG_PROC_FS
 struct ipc_proc_iter {
     struct ipc_namespace *ns;
     struct pid_namespace *pid_ns;
     struct ipc_proc_iface *iface;
 };
 
 struct pid_namespace *ipc_seq_pid_ns(struct seq_file *s)
 {
     struct ipc_proc_iter *iter = s->private;
     return iter->pid_ns;
 }
 
 /*
  * This routine locks the ipc structure found at least at position pos.
  */
 static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
                           loff_t *new_pos)
 {
     struct kern_ipc_perm *ipc = NULL;
     int max_idx = ipc_get_maxidx(ids);
 
     if (max_idx == -1 || pos > max_idx)
         goto out;
 
     for (; pos <= max_idx; pos++) {
         ipc = idr_find(&ids->ipcs_idr, pos);
         if (ipc != NULL) {
             rcu_read_lock();
             ipc_lock_object(ipc);
             break;
         }
     }
 out:
     *new_pos = pos + 1;
     return ipc;
 }
 
 static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
 {
     struct ipc_proc_iter *iter = s->private;
     struct ipc_proc_iface *iface = iter->iface;
     struct kern_ipc_perm *ipc = it;
 
     /* If we had an ipc id locked before, unlock it */
     if (ipc && ipc != SEQ_START_TOKEN)
         ipc_unlock(ipc);
 
     return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
 }
 
 /*
  * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
  * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
  */
 static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
 {
     struct ipc_proc_iter *iter = s->private;
     struct ipc_proc_iface *iface = iter->iface;
     struct ipc_ids *ids;
 
     ids = &iter->ns->ids[iface->ids];
 
     /*
      * Take the lock - this will be released by the corresponding
      * call to stop().
      */
     down_read(&ids->rwsem);
 
     /* pos < 0 is invalid */
     if (*pos < 0)
         return NULL;
 
     /* pos == 0 means header */
     if (*pos == 0)
         return SEQ_START_TOKEN;
 
     /* Find the (pos-1)th ipc */
     return sysvipc_find_ipc(ids, *pos - 1, pos);
 }
 
 static void sysvipc_proc_stop(struct seq_file *s, void *it)
 {
     struct kern_ipc_perm *ipc = it;
     struct ipc_proc_iter *iter = s->private;
     struct ipc_proc_iface *iface = iter->iface;
     struct ipc_ids *ids;
 
     /* If we had a locked structure, release it */
     if (ipc && ipc != SEQ_START_TOKEN)
         ipc_unlock(ipc);
 
     ids = &iter->ns->ids[iface->ids];
     /* Release the lock we took in start() */
     up_read(&ids->rwsem);
 }
 
 static int sysvipc_proc_show(struct seq_file *s, void *it)
 {
     struct ipc_proc_iter *iter = s->private;
     struct ipc_proc_iface *iface = iter->iface;
 
     if (it == SEQ_START_TOKEN) {
         seq_puts(s, iface->header);
         return 0;
     }
 
     return iface->show(s, it);
 }
 
 static const struct seq_operations sysvipc_proc_seqops = {
     .start = sysvipc_proc_start,
     .stop  = sysvipc_proc_stop,
     .next  = sysvipc_proc_next,
     .show  = sysvipc_proc_show,
 };
 
 static int sysvipc_proc_open(struct inode *inode, struct file *file)
 {
     struct ipc_proc_iter *iter;
 
     iter = __seq_open_private(file, &sysvipc_proc_seqops, sizeof(*iter));
     if (!iter)
         return -ENOMEM;
 
     iter->iface = pde_data(inode);
     iter->ns    = get_ipc_ns(current->nsproxy->ipc_ns);
     iter->pid_ns = get_pid_ns(task_active_pid_ns(current));
 
     return 0;
 }
 
 static int sysvipc_proc_release(struct inode *inode, struct file *file)
 {
     struct seq_file *seq = file->private_data;
     struct ipc_proc_iter *iter = seq->private;
     put_ipc_ns(iter->ns);
     put_pid_ns(iter->pid_ns);
     return seq_release_private(inode, file);
 }
 
 static const struct proc_ops sysvipc_proc_ops = {
     .proc_flags = PROC_ENTRY_PERMANENT,
     .proc_open  = sysvipc_proc_open,
     .proc_read  = seq_read,
     .proc_lseek = seq_lseek,
     .proc_release   = sysvipc_proc_release,
 };
 #endif /* CONFIG_PROC_FS */

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