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	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

 /*
  * POSIX message queues filesystem for Linux.
  *
  * Copyright (C) 2003,2004  Krzysztof Benedyczak    (golbi@mat.uni.torun.pl)
  *                          Michal Wronski          (michal.wronski@gmail.com)
  *
  * Spinlocks:               Mohamed Abbas           (abbas.mohamed@intel.com)
  * Lockless receive & send, fd based notify:
  *              Manfred Spraul      (manfred@colorfullife.com)
  *
  * Audit:                   George Wilson           (ltcgcw@us.ibm.com)
  *
  * This file is released under the GPL.
  */
 
 #include <linux/capability.h>
 #include <linux/init.h>
 #include <linux/pagemap.h>
 #include <linux/file.h>
 #include <linux/mount.h>
 #include <linux/fs_context.h>
 #include <linux/namei.h>
 #include <linux/sysctl.h>
 #include <linux/poll.h>
 #include <linux/mqueue.h>
 #include <linux/msg.h>
 #include <linux/skbuff.h>
 #include <linux/vmalloc.h>
 #include <linux/netlink.h>
 #include <linux/syscalls.h>
 #include <linux/audit.h>
 #include <linux/signal.h>
 #include <linux/mutex.h>
 #include <linux/nsproxy.h>
 #include <linux/pid.h>
 #include <linux/ipc_namespace.h>
 #include <linux/user_namespace.h>
 #include <linux/slab.h>
 #include <linux/sched/wake_q.h>
 #include <linux/sched/signal.h>
 #include <linux/sched/user.h>
 
 #include <net/sock.h>
 #include "util.h"
 
 struct mqueue_fs_context {
     struct ipc_namespace    *ipc_ns;
     bool             newns; /* Set if newly created ipc namespace */
 };
 
 #define MQUEUE_MAGIC    0x19800202
 #define DIRENT_SIZE 20
 #define FILENT_SIZE 80
 
 #define SEND        0
 #define RECV        1
 
 #define STATE_NONE  0
 #define STATE_READY 1
 
 struct posix_msg_tree_node {
     struct rb_node      rb_node;
     struct list_head    msg_list;
     int         priority;
 };
 
 /*
  * Locking:
  *
  * Accesses to a message queue are synchronized by acquiring info->lock.
  *
  * There are two notable exceptions:
  * - The actual wakeup of a sleeping task is performed using the wake_q
  *   framework. info->lock is already released when wake_up_q is called.
  * - The exit codepaths after sleeping check ext_wait_queue->state without
  *   any locks. If it is STATE_READY, then the syscall is completed without
  *   acquiring info->lock.
  *
  * MQ_BARRIER:
  * To achieve proper release/acquire memory barrier pairing, the state is set to
  * STATE_READY with smp_store_release(), and it is read with READ_ONCE followed
  * by smp_acquire__after_ctrl_dep(). In addition, wake_q_add_safe() is used.
  *
  * This prevents the following races:
  *
  * 1) With the simple wake_q_add(), the task could be gone already before
  *    the increase of the reference happens
  * Thread A
  *              Thread B
  * WRITE_ONCE(wait.state, STATE_NONE);
  * schedule_hrtimeout()
  *              wake_q_add(A)
  *              if (cmpxchg()) // success
  *                 ->state = STATE_READY (reordered)
  * <timeout returns>
  * if (wait.state == STATE_READY) return;
  * sysret to user space
  * sys_exit()
  *              get_task_struct() // UaF
  *
  * Solution: Use wake_q_add_safe() and perform the get_task_struct() before
  * the smp_store_release() that does ->state = STATE_READY.
  *
  * 2) Without proper _release/_acquire barriers, the woken up task
  *    could read stale data
  *
  * Thread A
  *              Thread B
  * do_mq_timedreceive
  * WRITE_ONCE(wait.state, STATE_NONE);
  * schedule_hrtimeout()
  *              state = STATE_READY;
  * <timeout returns>
  * if (wait.state == STATE_READY) return;
  * msg_ptr = wait.msg;      // Access to stale data!
  *              receiver->msg = message; (reordered)
  *
  * Solution: use _release and _acquire barriers.
  *
  * 3) There is intentionally no barrier when setting current->state
  *    to TASK_INTERRUPTIBLE: spin_unlock(&info->lock) provides the
  *    release memory barrier, and the wakeup is triggered when holding
  *    info->lock, i.e. spin_lock(&info->lock) provided a pairing
  *    acquire memory barrier.
  */
 
 struct ext_wait_queue {     /* queue of sleeping tasks */
     struct task_struct *task;
     struct list_head list;
     struct msg_msg *msg;    /* ptr of loaded message */
     int state;      /* one of STATE_* values */
 };
 
 struct mqueue_inode_info {
     spinlock_t lock;
     struct inode vfs_inode;
     wait_queue_head_t wait_q;
 
     struct rb_root msg_tree;
     struct rb_node *msg_tree_rightmost;
     struct posix_msg_tree_node *node_cache;
     struct mq_attr attr;
 
     struct sigevent notify;
     struct pid *notify_owner;
     u32 notify_self_exec_id;
     struct user_namespace *notify_user_ns;
     struct ucounts *ucounts;    /* user who created, for accounting */
     struct sock *notify_sock;
     struct sk_buff *notify_cookie;
 
     /* for tasks waiting for free space and messages, respectively */
     struct ext_wait_queue e_wait_q[2];
 
     unsigned long qsize; /* size of queue in memory (sum of all msgs) */
 };
 
 static struct file_system_type mqueue_fs_type;
 static const struct inode_operations mqueue_dir_inode_operations;
 static const struct file_operations mqueue_file_operations;
 static const struct super_operations mqueue_super_ops;
 static const struct fs_context_operations mqueue_fs_context_ops;
 static void remove_notification(struct mqueue_inode_info *info);
 
 static struct kmem_cache *mqueue_inode_cachep;
 
 static inline struct mqueue_inode_info *MQUEUE_I(struct inode *inode)
 {
     return container_of(inode, struct mqueue_inode_info, vfs_inode);
 }
 
 /*
  * This routine should be called with the mq_lock held.
  */
 static inline struct ipc_namespace *__get_ns_from_inode(struct inode *inode)
 {
     return get_ipc_ns(inode->i_sb->s_fs_info);
 }
 
 static struct ipc_namespace *get_ns_from_inode(struct inode *inode)
 {
     struct ipc_namespace *ns;
 
     spin_lock(&mq_lock);
     ns = __get_ns_from_inode(inode);
     spin_unlock(&mq_lock);
     return ns;
 }
 
 /* Auxiliary functions to manipulate messages' list */
 static int msg_insert(struct msg_msg *msg, struct mqueue_inode_info *info)
 {
     struct rb_node **p, *parent = NULL;
     struct posix_msg_tree_node *leaf;
     bool rightmost = true;
 
     p = &info->msg_tree.rb_node;
     while (*p) {
         parent = *p;
         leaf = rb_entry(parent, struct posix_msg_tree_node, rb_node);
 
         if (likely(leaf->priority == msg->m_type))
             goto insert_msg;
         else if (msg->m_type < leaf->priority) {
             p = &(*p)->rb_left;
             rightmost = false;
         } else
             p = &(*p)->rb_right;
     }
     if (info->node_cache) {
         leaf = info->node_cache;
         info->node_cache = NULL;
     } else {
         leaf = kmalloc(sizeof(*leaf), GFP_ATOMIC);
         if (!leaf)
             return -ENOMEM;
         INIT_LIST_HEAD(&leaf->msg_list);
     }
     leaf->priority = msg->m_type;
 
     if (rightmost)
         info->msg_tree_rightmost = &leaf->rb_node;
 
     rb_link_node(&leaf->rb_node, parent, p);
     rb_insert_color(&leaf->rb_node, &info->msg_tree);
 insert_msg:
     info->attr.mq_curmsgs++;
     info->qsize += msg->m_ts;
     list_add_tail(&msg->m_list, &leaf->msg_list);
     return 0;
 }
 
 static inline void msg_tree_erase(struct posix_msg_tree_node *leaf,
                   struct mqueue_inode_info *info)
 {
     struct rb_node *node = &leaf->rb_node;
 
     if (info->msg_tree_rightmost == node)
         info->msg_tree_rightmost = rb_prev(node);
 
     rb_erase(node, &info->msg_tree);
     if (info->node_cache)
         kfree(leaf);
     else
         info->node_cache = leaf;
 }
 
 static inline struct msg_msg *msg_get(struct mqueue_inode_info *info)
 {
     struct rb_node *parent = NULL;
     struct posix_msg_tree_node *leaf;
     struct msg_msg *msg;
 
 try_again:
     /*
      * During insert, low priorities go to the left and high to the
      * right.  On receive, we want the highest priorities first, so
      * walk all the way to the right.
      */
     parent = info->msg_tree_rightmost;
     if (!parent) {
         if (info->attr.mq_curmsgs) {
             pr_warn_once("Inconsistency in POSIX message queue, "
                      "no tree element, but supposedly messages "
                      "should exist!\n");
             info->attr.mq_curmsgs = 0;
         }
         return NULL;
     }
     leaf = rb_entry(parent, struct posix_msg_tree_node, rb_node);
     if (unlikely(list_empty(&leaf->msg_list))) {
         pr_warn_once("Inconsistency in POSIX message queue, "
                  "empty leaf node but we haven't implemented "
                  "lazy leaf delete!\n");
         msg_tree_erase(leaf, info);
         goto try_again;
     } else {
         msg = list_first_entry(&leaf->msg_list,
                        struct msg_msg, m_list);
         list_del(&msg->m_list);
         if (list_empty(&leaf->msg_list)) {
             msg_tree_erase(leaf, info);
         }
     }
     info->attr.mq_curmsgs--;
     info->qsize -= msg->m_ts;
     return msg;
 }
 
 static struct inode *mqueue_get_inode(struct super_block *sb,
         struct ipc_namespace *ipc_ns, umode_t mode,
         struct mq_attr *attr)
 {
     struct inode *inode;
     int ret = -ENOMEM;
 
     inode = new_inode(sb);
     if (!inode)
         goto err;
 
     inode->i_ino = get_next_ino();
     inode->i_mode = mode;
     inode->i_uid = current_fsuid();
     inode->i_gid = current_fsgid();
     inode->i_mtime = inode->i_ctime = inode->i_atime = current_time(inode);
 
     if (S_ISREG(mode)) {
         struct mqueue_inode_info *info;
         unsigned long mq_bytes, mq_treesize;
 
         inode->i_fop = &mqueue_file_operations;
         inode->i_size = FILENT_SIZE;
         /* mqueue specific info */
         info = MQUEUE_I(inode);
         spin_lock_init(&info->lock);
         init_waitqueue_head(&info->wait_q);
         INIT_LIST_HEAD(&info->e_wait_q[0].list);
         INIT_LIST_HEAD(&info->e_wait_q[1].list);
         info->notify_owner = NULL;
         info->notify_user_ns = NULL;
         info->qsize = 0;
         info->ucounts = NULL;   /* set when all is ok */
         info->msg_tree = RB_ROOT;
         info->msg_tree_rightmost = NULL;
         info->node_cache = NULL;
         memset(&info->attr, 0, sizeof(info->attr));
         info->attr.mq_maxmsg = min(ipc_ns->mq_msg_max,
                        ipc_ns->mq_msg_default);
         info->attr.mq_msgsize = min(ipc_ns->mq_msgsize_max,
                         ipc_ns->mq_msgsize_default);
         if (attr) {
             info->attr.mq_maxmsg = attr->mq_maxmsg;
             info->attr.mq_msgsize = attr->mq_msgsize;
         }
         /*
          * We used to allocate a static array of pointers and account
          * the size of that array as well as one msg_msg struct per
          * possible message into the queue size. That's no longer
          * accurate as the queue is now an rbtree and will grow and
          * shrink depending on usage patterns.  We can, however, still
          * account one msg_msg struct per message, but the nodes are
          * allocated depending on priority usage, and most programs
          * only use one, or a handful, of priorities.  However, since
          * this is pinned memory, we need to assume worst case, so
          * that means the min(mq_maxmsg, max_priorities) * struct
          * posix_msg_tree_node.
          */
 
         ret = -EINVAL;
         if (info->attr.mq_maxmsg <= 0 || info->attr.mq_msgsize <= 0)
             goto out_inode;
         if (capable(CAP_SYS_RESOURCE)) {
             if (info->attr.mq_maxmsg > HARD_MSGMAX ||
                 info->attr.mq_msgsize > HARD_MSGSIZEMAX)
                 goto out_inode;
         } else {
             if (info->attr.mq_maxmsg > ipc_ns->mq_msg_max ||
                     info->attr.mq_msgsize > ipc_ns->mq_msgsize_max)
                 goto out_inode;
         }
         ret = -EOVERFLOW;
         /* check for overflow */
         if (info->attr.mq_msgsize > ULONG_MAX/info->attr.mq_maxmsg)
             goto out_inode;
         mq_treesize = info->attr.mq_maxmsg * sizeof(struct msg_msg) +
             min_t(unsigned int, info->attr.mq_maxmsg, MQ_PRIO_MAX) *
             sizeof(struct posix_msg_tree_node);
         mq_bytes = info->attr.mq_maxmsg * info->attr.mq_msgsize;
         if (mq_bytes + mq_treesize < mq_bytes)
             goto out_inode;
         mq_bytes += mq_treesize;
         info->ucounts = get_ucounts(current_ucounts());
         if (info->ucounts) {
             long msgqueue;
 
             spin_lock(&mq_lock);
             msgqueue = inc_rlimit_ucounts(info->ucounts, UCOUNT_RLIMIT_MSGQUEUE, mq_bytes);
             if (msgqueue == LONG_MAX || msgqueue > rlimit(RLIMIT_MSGQUEUE)) {
                 dec_rlimit_ucounts(info->ucounts, UCOUNT_RLIMIT_MSGQUEUE, mq_bytes);
                 spin_unlock(&mq_lock);
                 put_ucounts(info->ucounts);
                 info->ucounts = NULL;
                 /* mqueue_evict_inode() releases info->messages */
                 ret = -EMFILE;
                 goto out_inode;
             }
             spin_unlock(&mq_lock);
         }
     } else if (S_ISDIR(mode)) {
         inc_nlink(inode);
         /* Some things misbehave if size == 0 on a directory */
         inode->i_size = 2 * DIRENT_SIZE;
         inode->i_op = &mqueue_dir_inode_operations;
         inode->i_fop = &simple_dir_operations;
     }
 
     return inode;
 out_inode:
     iput(inode);
 err:
     return ERR_PTR(ret);
 }
 
 static int mqueue_fill_super(struct super_block *sb, struct fs_context *fc)
 {
     struct inode *inode;
     struct ipc_namespace *ns = sb->s_fs_info;
 
     sb->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;
     sb->s_blocksize = PAGE_SIZE;
     sb->s_blocksize_bits = PAGE_SHIFT;
     sb->s_magic = MQUEUE_MAGIC;
     sb->s_op = &mqueue_super_ops;
 
     inode = mqueue_get_inode(sb, ns, S_IFDIR | S_ISVTX | S_IRWXUGO, NULL);
     if (IS_ERR(inode))
         return PTR_ERR(inode);
 
     sb->s_root = d_make_root(inode);
     if (!sb->s_root)
         return -ENOMEM;
     return 0;
 }
 
 static int mqueue_get_tree(struct fs_context *fc)
 {
     struct mqueue_fs_context *ctx = fc->fs_private;
 
     /*
      * With a newly created ipc namespace, we don't need to do a search
      * for an ipc namespace match, but we still need to set s_fs_info.
      */
     if (ctx->newns) {
         fc->s_fs_info = ctx->ipc_ns;
         return get_tree_nodev(fc, mqueue_fill_super);
     }
     return get_tree_keyed(fc, mqueue_fill_super, ctx->ipc_ns);
 }
 
 static void mqueue_fs_context_free(struct fs_context *fc)
 {
     struct mqueue_fs_context *ctx = fc->fs_private;
 
     put_ipc_ns(ctx->ipc_ns);
     kfree(ctx);
 }
 
 static int mqueue_init_fs_context(struct fs_context *fc)
 {
     struct mqueue_fs_context *ctx;
 
     ctx = kzalloc(sizeof(struct mqueue_fs_context), GFP_KERNEL);
     if (!ctx)
         return -ENOMEM;
 
     ctx->ipc_ns = get_ipc_ns(current->nsproxy->ipc_ns);
     put_user_ns(fc->user_ns);
     fc->user_ns = get_user_ns(ctx->ipc_ns->user_ns);
     fc->fs_private = ctx;
     fc->ops = &mqueue_fs_context_ops;
     return 0;
 }
 
 /*
  * mq_init_ns() is currently the only caller of mq_create_mount().
  * So the ns parameter is always a newly created ipc namespace.
  */
 static struct vfsmount *mq_create_mount(struct ipc_namespace *ns)
 {
     struct mqueue_fs_context *ctx;
     struct fs_context *fc;
     struct vfsmount *mnt;
 
     fc = fs_context_for_mount(&mqueue_fs_type, SB_KERNMOUNT);
     if (IS_ERR(fc))
         return ERR_CAST(fc);
 
     ctx = fc->fs_private;
     ctx->newns = true;
     put_ipc_ns(ctx->ipc_ns);
     ctx->ipc_ns = get_ipc_ns(ns);
     put_user_ns(fc->user_ns);
     fc->user_ns = get_user_ns(ctx->ipc_ns->user_ns);
 
     mnt = fc_mount(fc);
     put_fs_context(fc);
     return mnt;
 }
 
 static void init_once(void *foo)
 {
     struct mqueue_inode_info *p = foo;
 
     inode_init_once(&p->vfs_inode);
 }
 
 static struct inode *mqueue_alloc_inode(struct super_block *sb)
 {
     struct mqueue_inode_info *ei;
 
     ei = alloc_inode_sb(sb, mqueue_inode_cachep, GFP_KERNEL);
     if (!ei)
         return NULL;
     return &ei->vfs_inode;
 }
 
 static void mqueue_free_inode(struct inode *inode)
 {
     kmem_cache_free(mqueue_inode_cachep, MQUEUE_I(inode));
 }
 
 static void mqueue_evict_inode(struct inode *inode)
 {
     struct mqueue_inode_info *info;
     struct ipc_namespace *ipc_ns;
     struct msg_msg *msg, *nmsg;
     LIST_HEAD(tmp_msg);
 
     clear_inode(inode);
 
     if (S_ISDIR(inode->i_mode))
         return;
 
     ipc_ns = get_ns_from_inode(inode);
     info = MQUEUE_I(inode);
     spin_lock(&info->lock);
     while ((msg = msg_get(info)) != NULL)
         list_add_tail(&msg->m_list, &tmp_msg);
     kfree(info->node_cache);
     spin_unlock(&info->lock);
 
     list_for_each_entry_safe(msg, nmsg, &tmp_msg, m_list) {
         list_del(&msg->m_list);
         free_msg(msg);
     }
 
     if (info->ucounts) {
         unsigned long mq_bytes, mq_treesize;
 
         /* Total amount of bytes accounted for the mqueue */
         mq_treesize = info->attr.mq_maxmsg * sizeof(struct msg_msg) +
             min_t(unsigned int, info->attr.mq_maxmsg, MQ_PRIO_MAX) *
             sizeof(struct posix_msg_tree_node);
 
         mq_bytes = mq_treesize + (info->attr.mq_maxmsg *
                       info->attr.mq_msgsize);
 
         spin_lock(&mq_lock);
         dec_rlimit_ucounts(info->ucounts, UCOUNT_RLIMIT_MSGQUEUE, mq_bytes);
         /*
          * get_ns_from_inode() ensures that the
          * (ipc_ns = sb->s_fs_info) is either a valid ipc_ns
          * to which we now hold a reference, or it is NULL.
          * We can't put it here under mq_lock, though.
          */
         if (ipc_ns)
             ipc_ns->mq_queues_count--;
         spin_unlock(&mq_lock);
         put_ucounts(info->ucounts);
         info->ucounts = NULL;
     }
     if (ipc_ns)
         put_ipc_ns(ipc_ns);
 }
 
 static int mqueue_create_attr(struct dentry *dentry, umode_t mode, void *arg)
 {
     struct inode *dir = dentry->d_parent->d_inode;
     struct inode *inode;
     struct mq_attr *attr = arg;
     int error;
     struct ipc_namespace *ipc_ns;
 
     spin_lock(&mq_lock);
     ipc_ns = __get_ns_from_inode(dir);
     if (!ipc_ns) {
         error = -EACCES;
         goto out_unlock;
     }
 
     if (ipc_ns->mq_queues_count >= ipc_ns->mq_queues_max &&
         !capable(CAP_SYS_RESOURCE)) {
         error = -ENOSPC;
         goto out_unlock;
     }
     ipc_ns->mq_queues_count++;
     spin_unlock(&mq_lock);
 
     inode = mqueue_get_inode(dir->i_sb, ipc_ns, mode, attr);
     if (IS_ERR(inode)) {
         error = PTR_ERR(inode);
         spin_lock(&mq_lock);
         ipc_ns->mq_queues_count--;
         goto out_unlock;
     }
 
     put_ipc_ns(ipc_ns);
     dir->i_size += DIRENT_SIZE;
     dir->i_ctime = dir->i_mtime = dir->i_atime = current_time(dir);
 
     d_instantiate(dentry, inode);
     dget(dentry);
     return 0;
 out_unlock:
     spin_unlock(&mq_lock);
     if (ipc_ns)
         put_ipc_ns(ipc_ns);
     return error;
 }
 
 static int mqueue_create(struct user_namespace *mnt_userns, struct inode *dir,
              struct dentry *dentry, umode_t mode, bool excl)
 {
     return mqueue_create_attr(dentry, mode, NULL);
 }
 
 static int mqueue_unlink(struct inode *dir, struct dentry *dentry)
 {
     struct inode *inode = d_inode(dentry);
 
     dir->i_ctime = dir->i_mtime = dir->i_atime = current_time(dir);
     dir->i_size -= DIRENT_SIZE;
     drop_nlink(inode);
     dput(dentry);
     return 0;
 }
 
 /*
 *   This is routine for system read from queue file.
 *   To avoid mess with doing here some sort of mq_receive we allow
 *   to read only queue size & notification info (the only values
 *   that are interesting from user point of view and aren't accessible
 *   through std routines)
 */
 static ssize_t mqueue_read_file(struct file *filp, char __user *u_data,
                 size_t count, loff_t *off)
 {
     struct mqueue_inode_info *info = MQUEUE_I(file_inode(filp));
     char buffer[FILENT_SIZE];
     ssize_t ret;
 
     spin_lock(&info->lock);
     snprintf(buffer, sizeof(buffer),
             "QSIZE:%-10lu NOTIFY:%-5d SIGNO:%-5d NOTIFY_PID:%-6d\n",
             info->qsize,
             info->notify_owner ? info->notify.sigev_notify : 0,
             (info->notify_owner &&
              info->notify.sigev_notify == SIGEV_SIGNAL) ?
                 info->notify.sigev_signo : 0,
             pid_vnr(info->notify_owner));
     spin_unlock(&info->lock);
     buffer[sizeof(buffer)-1] = '\0';
 
     ret = simple_read_from_buffer(u_data, count, off, buffer,
                 strlen(buffer));
     if (ret <= 0)
         return ret;
 
     file_inode(filp)->i_atime = file_inode(filp)->i_ctime = current_time(file_inode(filp));
     return ret;
 }
 
 static int mqueue_flush_file(struct file *filp, fl_owner_t id)
 {
     struct mqueue_inode_info *info = MQUEUE_I(file_inode(filp));
 
     spin_lock(&info->lock);
     if (task_tgid(current) == info->notify_owner)
         remove_notification(info);
 
     spin_unlock(&info->lock);
     return 0;
 }
 
 static __poll_t mqueue_poll_file(struct file *filp, struct poll_table_struct *poll_tab)
 {
     struct mqueue_inode_info *info = MQUEUE_I(file_inode(filp));
     __poll_t retval = 0;
 
     poll_wait(filp, &info->wait_q, poll_tab);
 
     spin_lock(&info->lock);
     if (info->attr.mq_curmsgs)
         retval = EPOLLIN | EPOLLRDNORM;
 
     if (info->attr.mq_curmsgs < info->attr.mq_maxmsg)
         retval |= EPOLLOUT | EPOLLWRNORM;
     spin_unlock(&info->lock);
 
     return retval;
 }
 
 /* Adds current to info->e_wait_q[sr] before element with smaller prio */
 static void wq_add(struct mqueue_inode_info *info, int sr,
             struct ext_wait_queue *ewp)
 {
     struct ext_wait_queue *walk;
 
     list_for_each_entry(walk, &info->e_wait_q[sr].list, list) {
         if (walk->task->prio <= current->prio) {
             list_add_tail(&ewp->list, &walk->list);
             return;
         }
     }
     list_add_tail(&ewp->list, &info->e_wait_q[sr].list);
 }
 
 /*
  * Puts current task to sleep. Caller must hold queue lock. After return
  * lock isn't held.
  * sr: SEND or RECV
  */
 static int wq_sleep(struct mqueue_inode_info *info, int sr,
             ktime_t *timeout, struct ext_wait_queue *ewp)
     __releases(&info->lock)
 {
     int retval;
     signed long time;
 
     wq_add(info, sr, ewp);
 
     for (;;) {
         /* memory barrier not required, we hold info->lock */
         __set_current_state(TASK_INTERRUPTIBLE);
 
         spin_unlock(&info->lock);
         time = schedule_hrtimeout_range_clock(timeout, 0,
             HRTIMER_MODE_ABS, CLOCK_REALTIME);
 
         if (READ_ONCE(ewp->state) == STATE_READY) {
             /* see MQ_BARRIER for purpose/pairing */
             smp_acquire__after_ctrl_dep();
             retval = 0;
             goto out;
         }
         spin_lock(&info->lock);
 
         /* we hold info->lock, so no memory barrier required */
         if (READ_ONCE(ewp->state) == STATE_READY) {
             retval = 0;
             goto out_unlock;
         }
         if (signal_pending(current)) {
             retval = -ERESTARTSYS;
             break;
         }
         if (time == 0) {
             retval = -ETIMEDOUT;
             break;
         }
     }
     list_del(&ewp->list);
 out_unlock:
     spin_unlock(&info->lock);
 out:
     return retval;
 }
 
 /*
  * Returns waiting task that should be serviced first or NULL if none exists
  */
 static struct ext_wait_queue *wq_get_first_waiter(
         struct mqueue_inode_info *info, int sr)
 {
     struct list_head *ptr;
 
     ptr = info->e_wait_q[sr].list.prev;
     if (ptr == &info->e_wait_q[sr].list)
         return NULL;
     return list_entry(ptr, struct ext_wait_queue, list);
 }
 
 
 static inline void set_cookie(struct sk_buff *skb, char code)
 {
     ((char *)skb->data)[NOTIFY_COOKIE_LEN-1] = code;
 }
 
 /*
  * The next function is only to split too long sys_mq_timedsend
  */
 static void __do_notify(struct mqueue_inode_info *info)
 {
     /* notification
      * invoked when there is registered process and there isn't process
      * waiting synchronously for message AND state of queue changed from
      * empty to not empty. Here we are sure that no one is waiting
      * synchronously. */
     if (info->notify_owner &&
         info->attr.mq_curmsgs == 1) {
         switch (info->notify.sigev_notify) {
         case SIGEV_NONE:
             break;
         case SIGEV_SIGNAL: {
             struct kernel_siginfo sig_i;
             struct task_struct *task;
 
             /* do_mq_notify() accepts sigev_signo == 0, why?? */
             if (!info->notify.sigev_signo)
                 break;
 
             clear_siginfo(&sig_i);
             sig_i.si_signo = info->notify.sigev_signo;
             sig_i.si_errno = 0;
             sig_i.si_code = SI_MESGQ;
             sig_i.si_value = info->notify.sigev_value;
             rcu_read_lock();
             /* map current pid/uid into info->owner's namespaces */
             sig_i.si_pid = task_tgid_nr_ns(current,
                         ns_of_pid(info->notify_owner));
             sig_i.si_uid = from_kuid_munged(info->notify_user_ns,
                         current_uid());
             /*
              * We can't use kill_pid_info(), this signal should
              * bypass check_kill_permission(). It is from kernel
              * but si_fromuser() can't know this.
              * We do check the self_exec_id, to avoid sending
              * signals to programs that don't expect them.
              */
             task = pid_task(info->notify_owner, PIDTYPE_TGID);
             if (task && task->self_exec_id ==
                         info->notify_self_exec_id) {
                 do_send_sig_info(info->notify.sigev_signo,
                         &sig_i, task, PIDTYPE_TGID);
             }
             rcu_read_unlock();
             break;
         }
         case SIGEV_THREAD:
             set_cookie(info->notify_cookie, NOTIFY_WOKENUP);
             netlink_sendskb(info->notify_sock, info->notify_cookie);
             break;
         }
         /* after notification unregisters process */
         put_pid(info->notify_owner);
         put_user_ns(info->notify_user_ns);
         info->notify_owner = NULL;
         info->notify_user_ns = NULL;
     }
     wake_up(&info->wait_q);
 }
 
 static int prepare_timeout(const struct __kernel_timespec __user *u_abs_timeout,
                struct timespec64 *ts)
 {
     if (get_timespec64(ts, u_abs_timeout))
         return -EFAULT;
     if (!timespec64_valid(ts))
         return -EINVAL;
     return 0;
 }
 
 static void remove_notification(struct mqueue_inode_info *info)
 {
     if (info->notify_owner != NULL &&
         info->notify.sigev_notify == SIGEV_THREAD) {
         set_cookie(info->notify_cookie, NOTIFY_REMOVED);
         netlink_sendskb(info->notify_sock, info->notify_cookie);
     }
     put_pid(info->notify_owner);
     put_user_ns(info->notify_user_ns);
     info->notify_owner = NULL;
     info->notify_user_ns = NULL;
 }
 
 static int prepare_open(struct dentry *dentry, int oflag, int ro,
             umode_t mode, struct filename *name,
             struct mq_attr *attr)
 {
     static const int oflag2acc[O_ACCMODE] = { MAY_READ, MAY_WRITE,
                           MAY_READ | MAY_WRITE };
     int acc;
 
     if (d_really_is_negative(dentry)) {
         if (!(oflag & O_CREAT))
             return -ENOENT;
         if (ro)
             return ro;
         audit_inode_parent_hidden(name, dentry->d_parent);
         return vfs_mkobj(dentry, mode & ~current_umask(),
                   mqueue_create_attr, attr);
     }
     /* it already existed */
     audit_inode(name, dentry, 0);
     if ((oflag & (O_CREAT|O_EXCL)) == (O_CREAT|O_EXCL))
         return -EEXIST;
     if ((oflag & O_ACCMODE) == (O_RDWR | O_WRONLY))
         return -EINVAL;
     acc = oflag2acc[oflag & O_ACCMODE];
     return inode_permission(&init_user_ns, d_inode(dentry), acc);
 }
 
 static int do_mq_open(const char __user *u_name, int oflag, umode_t mode,
               struct mq_attr *attr)
 {
     struct vfsmount *mnt = current->nsproxy->ipc_ns->mq_mnt;
     struct dentry *root = mnt->mnt_root;
     struct filename *name;
     struct path path;
     int fd, error;
     int ro;
 
     audit_mq_open(oflag, mode, attr);
 
     if (IS_ERR(name = getname(u_name)))
         return PTR_ERR(name);
 
     fd = get_unused_fd_flags(O_CLOEXEC);
     if (fd < 0)
         goto out_putname;
 
     ro = mnt_want_write(mnt);   /* we'll drop it in any case */
     inode_lock(d_inode(root));
     path.dentry = lookup_one_len(name->name, root, strlen(name->name));
     if (IS_ERR(path.dentry)) {
         error = PTR_ERR(path.dentry);
         goto out_putfd;
     }
     path.mnt = mntget(mnt);
     error = prepare_open(path.dentry, oflag, ro, mode, name, attr);
     if (!error) {
         struct file *file = dentry_open(&path, oflag, current_cred());
         if (!IS_ERR(file))
             fd_install(fd, file);
         else
             error = PTR_ERR(file);
     }
     path_put(&path);
 out_putfd:
     if (error) {
         put_unused_fd(fd);
         fd = error;
     }
     inode_unlock(d_inode(root));
     if (!ro)
         mnt_drop_write(mnt);
 out_putname:
     putname(name);
     return fd;
 }
 
 SYSCALL_DEFINE4(mq_open, const char __user *, u_name, int, oflag, umode_t, mode,
         struct mq_attr __user *, u_attr)
 {
     struct mq_attr attr;
     if (u_attr && copy_from_user(&attr, u_attr, sizeof(struct mq_attr)))
         return -EFAULT;
 
     return do_mq_open(u_name, oflag, mode, u_attr ? &attr : NULL);
 }
 
 SYSCALL_DEFINE1(mq_unlink, const char __user *, u_name)
 {
     int err;
     struct filename *name;
     struct dentry *dentry;
     struct inode *inode = NULL;
     struct ipc_namespace *ipc_ns = current->nsproxy->ipc_ns;
     struct vfsmount *mnt = ipc_ns->mq_mnt;
 
     name = getname(u_name);
     if (IS_ERR(name))
         return PTR_ERR(name);
 
     audit_inode_parent_hidden(name, mnt->mnt_root);
     err = mnt_want_write(mnt);
     if (err)
         goto out_name;
     inode_lock_nested(d_inode(mnt->mnt_root), I_MUTEX_PARENT);
     dentry = lookup_one_len(name->name, mnt->mnt_root,
                 strlen(name->name));
     if (IS_ERR(dentry)) {
         err = PTR_ERR(dentry);
         goto out_unlock;
     }
 
     inode = d_inode(dentry);
     if (!inode) {
         err = -ENOENT;
     } else {
         ihold(inode);
         err = vfs_unlink(&init_user_ns, d_inode(dentry->d_parent),
                  dentry, NULL);
     }
     dput(dentry);
 
 out_unlock:
     inode_unlock(d_inode(mnt->mnt_root));
     if (inode)
         iput(inode);
     mnt_drop_write(mnt);
 out_name:
     putname(name);
 
     return err;
 }
 
 /* Pipelined send and receive functions.
  *
  * If a receiver finds no waiting message, then it registers itself in the
  * list of waiting receivers. A sender checks that list before adding the new
  * message into the message array. If there is a waiting receiver, then it
  * bypasses the message array and directly hands the message over to the
  * receiver. The receiver accepts the message and returns without grabbing the
  * queue spinlock:
  *
  * - Set pointer to message.
  * - Queue the receiver task for later wakeup (without the info->lock).
  * - Update its state to STATE_READY. Now the receiver can continue.
  * - Wake up the process after the lock is dropped. Should the process wake up
  *   before this wakeup (due to a timeout or a signal) it will either see
  *   STATE_READY and continue or acquire the lock to check the state again.
  *
  * The same algorithm is used for senders.
  */
 
 static inline void __pipelined_op(struct wake_q_head *wake_q,
                   struct mqueue_inode_info *info,
                   struct ext_wait_queue *this)
 {
     struct task_struct *task;
 
     list_del(&this->list);
     task = get_task_struct(this->task);
 
     /* see MQ_BARRIER for purpose/pairing */
     smp_store_release(&this->state, STATE_READY);
     wake_q_add_safe(wake_q, task);
 }
 
 /* pipelined_send() - send a message directly to the task waiting in
  * sys_mq_timedreceive() (without inserting message into a queue).
  */
 static inline void pipelined_send(struct wake_q_head *wake_q,
                   struct mqueue_inode_info *info,
                   struct msg_msg *message,
                   struct ext_wait_queue *receiver)
 {
     receiver->msg = message;
     __pipelined_op(wake_q, info, receiver);
 }
 
 /* pipelined_receive() - if there is task waiting in sys_mq_timedsend()
  * gets its message and put to the queue (we have one free place for sure). */
 static inline void pipelined_receive(struct wake_q_head *wake_q,
                      struct mqueue_inode_info *info)
 {
     struct ext_wait_queue *sender = wq_get_first_waiter(info, SEND);
 
     if (!sender) {
         /* for poll */
         wake_up_interruptible(&info->wait_q);
         return;
     }
     if (msg_insert(sender->msg, info))
         return;
 
     __pipelined_op(wake_q, info, sender);
 }
 
 static int do_mq_timedsend(mqd_t mqdes, const char __user *u_msg_ptr,
         size_t msg_len, unsigned int msg_prio,
         struct timespec64 *ts)
 {
     struct fd f;
     struct inode *inode;
     struct ext_wait_queue wait;
     struct ext_wait_queue *receiver;
     struct msg_msg *msg_ptr;
     struct mqueue_inode_info *info;
     ktime_t expires, *timeout = NULL;
     struct posix_msg_tree_node *new_leaf = NULL;
     int ret = 0;
     DEFINE_WAKE_Q(wake_q);
 
     if (unlikely(msg_prio >= (unsigned long) MQ_PRIO_MAX))
         return -EINVAL;
 
     if (ts) {
         expires = timespec64_to_ktime(*ts);
         timeout = &expires;
     }
 
     audit_mq_sendrecv(mqdes, msg_len, msg_prio, ts);
 
     f = fdget(mqdes);
     if (unlikely(!f.file)) {
         ret = -EBADF;
         goto out;
     }
 
     inode = file_inode(f.file);
     if (unlikely(f.file->f_op != &mqueue_file_operations)) {
         ret = -EBADF;
         goto out_fput;
     }
     info = MQUEUE_I(inode);
     audit_file(f.file);
 
     if (unlikely(!(f.file->f_mode & FMODE_WRITE))) {
         ret = -EBADF;
         goto out_fput;
     }
 
     if (unlikely(msg_len > info->attr.mq_msgsize)) {
         ret = -EMSGSIZE;
         goto out_fput;
     }
 
     /* First try to allocate memory, before doing anything with
      * existing queues. */
     msg_ptr = load_msg(u_msg_ptr, msg_len);
     if (IS_ERR(msg_ptr)) {
         ret = PTR_ERR(msg_ptr);
         goto out_fput;
     }
     msg_ptr->m_ts = msg_len;
     msg_ptr->m_type = msg_prio;
 
     /*
      * msg_insert really wants us to have a valid, spare node struct so
      * it doesn't have to kmalloc a GFP_ATOMIC allocation, but it will
      * fall back to that if necessary.
      */
     if (!info->node_cache)
         new_leaf = kmalloc(sizeof(*new_leaf), GFP_KERNEL);
 
     spin_lock(&info->lock);
 
     if (!info->node_cache && new_leaf) {
         /* Save our speculative allocation into the cache */
         INIT_LIST_HEAD(&new_leaf->msg_list);
         info->node_cache = new_leaf;
         new_leaf = NULL;
     } else {
         kfree(new_leaf);
     }
 
     if (info->attr.mq_curmsgs == info->attr.mq_maxmsg) {
         if (f.file->f_flags & O_NONBLOCK) {
             ret = -EAGAIN;
         } else {
             wait.task = current;
             wait.msg = (void *) msg_ptr;
 
             /* memory barrier not required, we hold info->lock */
             WRITE_ONCE(wait.state, STATE_NONE);
             ret = wq_sleep(info, SEND, timeout, &wait);
             /*
              * wq_sleep must be called with info->lock held, and
              * returns with the lock released
              */
             goto out_free;
         }
     } else {
         receiver = wq_get_first_waiter(info, RECV);
         if (receiver) {
             pipelined_send(&wake_q, info, msg_ptr, receiver);
         } else {
             /* adds message to the queue */
             ret = msg_insert(msg_ptr, info);
             if (ret)
                 goto out_unlock;
             __do_notify(info);
         }
         inode->i_atime = inode->i_mtime = inode->i_ctime =
                 current_time(inode);
     }
 out_unlock:
     spin_unlock(&info->lock);
     wake_up_q(&wake_q);
 out_free:
     if (ret)
         free_msg(msg_ptr);
 out_fput:
     fdput(f);
 out:
     return ret;
 }
 
 static int do_mq_timedreceive(mqd_t mqdes, char __user *u_msg_ptr,
         size_t msg_len, unsigned int __user *u_msg_prio,
         struct timespec64 *ts)
 {
     ssize_t ret;
     struct msg_msg *msg_ptr;
     struct fd f;
     struct inode *inode;
     struct mqueue_inode_info *info;
     struct ext_wait_queue wait;
     ktime_t expires, *timeout = NULL;
     struct posix_msg_tree_node *new_leaf = NULL;
 
     if (ts) {
         expires = timespec64_to_ktime(*ts);
         timeout = &expires;
     }
 
     audit_mq_sendrecv(mqdes, msg_len, 0, ts);
 
     f = fdget(mqdes);
     if (unlikely(!f.file)) {
         ret = -EBADF;
         goto out;
     }
 
     inode = file_inode(f.file);
     if (unlikely(f.file->f_op != &mqueue_file_operations)) {
         ret = -EBADF;
         goto out_fput;
     }
     info = MQUEUE_I(inode);
     audit_file(f.file);
 
     if (unlikely(!(f.file->f_mode & FMODE_READ))) {
         ret = -EBADF;
         goto out_fput;
     }
 
     /* checks if buffer is big enough */
     if (unlikely(msg_len < info->attr.mq_msgsize)) {
         ret = -EMSGSIZE;
         goto out_fput;
     }
 
     /*
      * msg_insert really wants us to have a valid, spare node struct so
      * it doesn't have to kmalloc a GFP_ATOMIC allocation, but it will
      * fall back to that if necessary.
      */
     if (!info->node_cache)
         new_leaf = kmalloc(sizeof(*new_leaf), GFP_KERNEL);
 
     spin_lock(&info->lock);
 
     if (!info->node_cache && new_leaf) {
         /* Save our speculative allocation into the cache */
         INIT_LIST_HEAD(&new_leaf->msg_list);
         info->node_cache = new_leaf;
     } else {
         kfree(new_leaf);
     }
 
     if (info->attr.mq_curmsgs == 0) {
         if (f.file->f_flags & O_NONBLOCK) {
             spin_unlock(&info->lock);
             ret = -EAGAIN;
         } else {
             wait.task = current;
 
             /* memory barrier not required, we hold info->lock */
             WRITE_ONCE(wait.state, STATE_NONE);
             ret = wq_sleep(info, RECV, timeout, &wait);
             msg_ptr = wait.msg;
         }
     } else {
         DEFINE_WAKE_Q(wake_q);
 
         msg_ptr = msg_get(info);
 
         inode->i_atime = inode->i_mtime = inode->i_ctime =
                 current_time(inode);
 
         /* There is now free space in queue. */
         pipelined_receive(&wake_q, info);
         spin_unlock(&info->lock);
         wake_up_q(&wake_q);
         ret = 0;
     }
     if (ret == 0) {
         ret = msg_ptr->m_ts;
 
         if ((u_msg_prio && put_user(msg_ptr->m_type, u_msg_prio)) ||
             store_msg(u_msg_ptr, msg_ptr, msg_ptr->m_ts)) {
             ret = -EFAULT;
         }
         free_msg(msg_ptr);
     }
 out_fput:
     fdput(f);
 out:
     return ret;
 }
 
 SYSCALL_DEFINE5(mq_timedsend, mqd_t, mqdes, const char __user *, u_msg_ptr,
         size_t, msg_len, unsigned int, msg_prio,
         const struct __kernel_timespec __user *, u_abs_timeout)
 {
     struct timespec64 ts, *p = NULL;
     if (u_abs_timeout) {
         int res = prepare_timeout(u_abs_timeout, &ts);
         if (res)
             return res;
         p = &ts;
     }
     return do_mq_timedsend(mqdes, u_msg_ptr, msg_len, msg_prio, p);
 }
 
 SYSCALL_DEFINE5(mq_timedreceive, mqd_t, mqdes, char __user *, u_msg_ptr,
         size_t, msg_len, unsigned int __user *, u_msg_prio,
         const struct __kernel_timespec __user *, u_abs_timeout)
 {
     struct timespec64 ts, *p = NULL;
     if (u_abs_timeout) {
         int res = prepare_timeout(u_abs_timeout, &ts);
         if (res)
             return res;
         p = &ts;
     }
     return do_mq_timedreceive(mqdes, u_msg_ptr, msg_len, u_msg_prio, p);
 }
 
 /*
  * Notes: the case when user wants us to deregister (with NULL as pointer)
  * and he isn't currently owner of notification, will be silently discarded.
  * It isn't explicitly defined in the POSIX.
  */
 static int do_mq_notify(mqd_t mqdes, const struct sigevent *notification)
 {
     int ret;
     struct fd f;
     struct sock *sock;
     struct inode *inode;
     struct mqueue_inode_info *info;
     struct sk_buff *nc;
 
     audit_mq_notify(mqdes, notification);
 
     nc = NULL;
     sock = NULL;
     if (notification != NULL) {
         if (unlikely(notification->sigev_notify != SIGEV_NONE &&
                  notification->sigev_notify != SIGEV_SIGNAL &&
                  notification->sigev_notify != SIGEV_THREAD))
             return -EINVAL;
         if (notification->sigev_notify == SIGEV_SIGNAL &&
             !valid_signal(notification->sigev_signo)) {
             return -EINVAL;
         }
         if (notification->sigev_notify == SIGEV_THREAD) {
             long timeo;
 
             /* create the notify skb */
             nc = alloc_skb(NOTIFY_COOKIE_LEN, GFP_KERNEL);
             if (!nc)
                 return -ENOMEM;
 
             if (copy_from_user(nc->data,
                     notification->sigev_value.sival_ptr,
                     NOTIFY_COOKIE_LEN)) {
                 ret = -EFAULT;
                 goto free_skb;
             }
 
             /* TODO: add a header? */
             skb_put(nc, NOTIFY_COOKIE_LEN);
             /* and attach it to the socket */
 retry:
             f = fdget(notification->sigev_signo);
             if (!f.file) {
                 ret = -EBADF;
                 goto out;
             }
             sock = netlink_getsockbyfilp(f.file);
             fdput(f);
             if (IS_ERR(sock)) {
                 ret = PTR_ERR(sock);
                 goto free_skb;
             }
 
             timeo = MAX_SCHEDULE_TIMEOUT;
             ret = netlink_attachskb(sock, nc, &timeo, NULL);
             if (ret == 1) {
                 sock = NULL;
                 goto retry;
             }
             if (ret)
                 return ret;
         }
     }
 
     f = fdget(mqdes);
     if (!f.file) {
         ret = -EBADF;
         goto out;
     }
 
     inode = file_inode(f.file);
     if (unlikely(f.file->f_op != &mqueue_file_operations)) {
         ret = -EBADF;
         goto out_fput;
     }
     info = MQUEUE_I(inode);
 
     ret = 0;
     spin_lock(&info->lock);
     if (notification == NULL) {
         if (info->notify_owner == task_tgid(current)) {
             remove_notification(info);
             inode->i_atime = inode->i_ctime = current_time(inode);
         }
     } else if (info->notify_owner != NULL) {
         ret = -EBUSY;
     } else {
         switch (notification->sigev_notify) {
         case SIGEV_NONE:
             info->notify.sigev_notify = SIGEV_NONE;
             break;
         case SIGEV_THREAD:
             info->notify_sock = sock;
             info->notify_cookie = nc;
             sock = NULL;
             nc = NULL;
             info->notify.sigev_notify = SIGEV_THREAD;
             break;
         case SIGEV_SIGNAL:
             info->notify.sigev_signo = notification->sigev_signo;
             info->notify.sigev_value = notification->sigev_value;
             info->notify.sigev_notify = SIGEV_SIGNAL;
             info->notify_self_exec_id = current->self_exec_id;
             break;
         }
 
         info->notify_owner = get_pid(task_tgid(current));
         info->notify_user_ns = get_user_ns(current_user_ns());
         inode->i_atime = inode->i_ctime = current_time(inode);
     }
     spin_unlock(&info->lock);
 out_fput:
     fdput(f);
 out:
     if (sock)
         netlink_detachskb(sock, nc);
     else
 free_skb:
         dev_kfree_skb(nc);
 
     return ret;
 }
 
 SYSCALL_DEFINE2(mq_notify, mqd_t, mqdes,
         const struct sigevent __user *, u_notification)
 {
     struct sigevent n, *p = NULL;
     if (u_notification) {
         if (copy_from_user(&n, u_notification, sizeof(struct sigevent)))
             return -EFAULT;
         p = &n;
     }
     return do_mq_notify(mqdes, p);
 }
 
 static int do_mq_getsetattr(int mqdes, struct mq_attr *new, struct mq_attr *old)
 {
     struct fd f;
     struct inode *inode;
     struct mqueue_inode_info *info;
 
     if (new && (new->mq_flags & (~O_NONBLOCK)))
         return -EINVAL;
 
     f = fdget(mqdes);
     if (!f.file)
         return -EBADF;
 
     if (unlikely(f.file->f_op != &mqueue_file_operations)) {
         fdput(f);
         return -EBADF;
     }
 
     inode = file_inode(f.file);
     info = MQUEUE_I(inode);
 
     spin_lock(&info->lock);
 
     if (old) {
         *old = info->attr;
         old->mq_flags = f.file->f_flags & O_NONBLOCK;
     }
     if (new) {
         audit_mq_getsetattr(mqdes, new);
         spin_lock(&f.file->f_lock);
         if (new->mq_flags & O_NONBLOCK)
             f.file->f_flags |= O_NONBLOCK;
         else
             f.file->f_flags &= ~O_NONBLOCK;
         spin_unlock(&f.file->f_lock);
 
         inode->i_atime = inode->i_ctime = current_time(inode);
     }
 
     spin_unlock(&info->lock);
     fdput(f);
     return 0;
 }
 
 SYSCALL_DEFINE3(mq_getsetattr, mqd_t, mqdes,
         const struct mq_attr __user *, u_mqstat,
         struct mq_attr __user *, u_omqstat)
 {
     int ret;
     struct mq_attr mqstat, omqstat;
     struct mq_attr *new = NULL, *old = NULL;
 
     if (u_mqstat) {
         new = &mqstat;
         if (copy_from_user(new, u_mqstat, sizeof(struct mq_attr)))
             return -EFAULT;
     }
     if (u_omqstat)
         old = &omqstat;
 
     ret = do_mq_getsetattr(mqdes, new, old);
     if (ret || !old)
         return ret;
 
     if (copy_to_user(u_omqstat, old, sizeof(struct mq_attr)))
         return -EFAULT;
     return 0;
 }
 
 #ifdef CONFIG_COMPAT
 
 struct compat_mq_attr {
     compat_long_t mq_flags;      /* message queue flags          */
     compat_long_t mq_maxmsg;     /* maximum number of messages       */
     compat_long_t mq_msgsize;    /* maximum message size             */
     compat_long_t mq_curmsgs;    /* number of messages currently queued  */
     compat_long_t __reserved[4]; /* ignored for input, zeroed for output */
 };
 
 static inline int get_compat_mq_attr(struct mq_attr *attr,
             const struct compat_mq_attr __user *uattr)
 {
     struct compat_mq_attr v;
 
     if (copy_from_user(&v, uattr, sizeof(*uattr)))
         return -EFAULT;
 
     memset(attr, 0, sizeof(*attr));
     attr->mq_flags = v.mq_flags;
     attr->mq_maxmsg = v.mq_maxmsg;
     attr->mq_msgsize = v.mq_msgsize;
     attr->mq_curmsgs = v.mq_curmsgs;
     return 0;
 }
 
 static inline int put_compat_mq_attr(const struct mq_attr *attr,
             struct compat_mq_attr __user *uattr)
 {
     struct compat_mq_attr v;
 
     memset(&v, 0, sizeof(v));
     v.mq_flags = attr->mq_flags;
     v.mq_maxmsg = attr->mq_maxmsg;
     v.mq_msgsize = attr->mq_msgsize;
     v.mq_curmsgs = attr->mq_curmsgs;
     if (copy_to_user(uattr, &v, sizeof(*uattr)))
         return -EFAULT;
     return 0;
 }
 
 COMPAT_SYSCALL_DEFINE4(mq_open, const char __user *, u_name,
                int, oflag, compat_mode_t, mode,
                struct compat_mq_attr __user *, u_attr)
 {
     struct mq_attr attr, *p = NULL;
     if (u_attr && oflag & O_CREAT) {
         p = &attr;
         if (get_compat_mq_attr(&attr, u_attr))
             return -EFAULT;
     }
     return do_mq_open(u_name, oflag, mode, p);
 }
 
 COMPAT_SYSCALL_DEFINE2(mq_notify, mqd_t, mqdes,
                const struct compat_sigevent __user *, u_notification)
 {
     struct sigevent n, *p = NULL;
     if (u_notification) {
         if (get_compat_sigevent(&n, u_notification))
             return -EFAULT;
         if (n.sigev_notify == SIGEV_THREAD)
             n.sigev_value.sival_ptr = compat_ptr(n.sigev_value.sival_int);
         p = &n;
     }
     return do_mq_notify(mqdes, p);
 }
 
 COMPAT_SYSCALL_DEFINE3(mq_getsetattr, mqd_t, mqdes,
                const struct compat_mq_attr __user *, u_mqstat,
                struct compat_mq_attr __user *, u_omqstat)
 {
     int ret;
     struct mq_attr mqstat, omqstat;
     struct mq_attr *new = NULL, *old = NULL;
 
     if (u_mqstat) {
         new = &mqstat;
         if (get_compat_mq_attr(new, u_mqstat))
             return -EFAULT;
     }
     if (u_omqstat)
         old = &omqstat;
 
     ret = do_mq_getsetattr(mqdes, new, old);
     if (ret || !old)
         return ret;
 
     if (put_compat_mq_attr(old, u_omqstat))
         return -EFAULT;
     return 0;
 }
 #endif
 
 #ifdef CONFIG_COMPAT_32BIT_TIME
 static int compat_prepare_timeout(const struct old_timespec32 __user *p,
                    struct timespec64 *ts)
 {
     if (get_old_timespec32(ts, p))
         return -EFAULT;
     if (!timespec64_valid(ts))
         return -EINVAL;
     return 0;
 }
 
 SYSCALL_DEFINE5(mq_timedsend_time32, mqd_t, mqdes,
         const char __user *, u_msg_ptr,
         unsigned int, msg_len, unsigned int, msg_prio,
         const struct old_timespec32 __user *, u_abs_timeout)
 {
     struct timespec64 ts, *p = NULL;
     if (u_abs_timeout) {
         int res = compat_prepare_timeout(u_abs_timeout, &ts);
         if (res)
             return res;
         p = &ts;
     }
     return do_mq_timedsend(mqdes, u_msg_ptr, msg_len, msg_prio, p);
 }
 
 SYSCALL_DEFINE5(mq_timedreceive_time32, mqd_t, mqdes,
         char __user *, u_msg_ptr,
         unsigned int, msg_len, unsigned int __user *, u_msg_prio,
         const struct old_timespec32 __user *, u_abs_timeout)
 {
     struct timespec64 ts, *p = NULL;
     if (u_abs_timeout) {
         int res = compat_prepare_timeout(u_abs_timeout, &ts);
         if (res)
             return res;
         p = &ts;
     }
     return do_mq_timedreceive(mqdes, u_msg_ptr, msg_len, u_msg_prio, p);
 }
 #endif
 
 static const struct inode_operations mqueue_dir_inode_operations = {
     .lookup = simple_lookup,
     .create = mqueue_create,
     .unlink = mqueue_unlink,
 };
 
 static const struct file_operations mqueue_file_operations = {
     .flush = mqueue_flush_file,
     .poll = mqueue_poll_file,
     .read = mqueue_read_file,
     .llseek = default_llseek,
 };
 
 static const struct super_operations mqueue_super_ops = {
     .alloc_inode = mqueue_alloc_inode,
     .free_inode = mqueue_free_inode,
     .evict_inode = mqueue_evict_inode,
     .statfs = simple_statfs,
 };
 
 static const struct fs_context_operations mqueue_fs_context_ops = {
     .free       = mqueue_fs_context_free,
     .get_tree   = mqueue_get_tree,
 };
 
 static struct file_system_type mqueue_fs_type = {
     .name           = "mqueue",
     .init_fs_context    = mqueue_init_fs_context,
     .kill_sb        = kill_litter_super,
     .fs_flags       = FS_USERNS_MOUNT,
 };
 
 int mq_init_ns(struct ipc_namespace *ns)
 {
     struct vfsmount *m;
 
     ns->mq_queues_count  = 0;
     ns->mq_queues_max    = DFLT_QUEUESMAX;
     ns->mq_msg_max       = DFLT_MSGMAX;
     ns->mq_msgsize_max   = DFLT_MSGSIZEMAX;
     ns->mq_msg_default   = DFLT_MSG;
     ns->mq_msgsize_default  = DFLT_MSGSIZE;
 
     m = mq_create_mount(ns);
     if (IS_ERR(m))
         return PTR_ERR(m);
     ns->mq_mnt = m;
     return 0;
 }
 
 void mq_clear_sbinfo(struct ipc_namespace *ns)
 {
     ns->mq_mnt->mnt_sb->s_fs_info = NULL;
 }
 
 void mq_put_mnt(struct ipc_namespace *ns)
 {
     kern_unmount(ns->mq_mnt);
 }
 
 static int __init init_mqueue_fs(void)
 {
     int error;
 
     mqueue_inode_cachep = kmem_cache_create("mqueue_inode_cache",
                 sizeof(struct mqueue_inode_info), 0,
                 SLAB_HWCACHE_ALIGN|SLAB_ACCOUNT, init_once);
     if (mqueue_inode_cachep == NULL)
         return -ENOMEM;
 
     if (!setup_mq_sysctls(&init_ipc_ns)) {
         pr_warn("sysctl registration failed\n");
         return -ENOMEM;
     }
 
     error = register_filesystem(&mqueue_fs_type);
     if (error)
         goto out_sysctl;
 
     spin_lock_init(&mq_lock);
 
     error = mq_init_ns(&init_ipc_ns);
     if (error)
         goto out_filesystem;
 
     return 0;
 
 out_filesystem:
     unregister_filesystem(&mqueue_fs_type);
 out_sysctl:
     kmem_cache_destroy(mqueue_inode_cachep);
     return error;
 }
 
 device_initcall(init_mqueue_fs);

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