Commit 073f6552 authored by Jan Kara's avatar Jan Kara Committed by Linus Torvalds
Browse files

fanotify: use notification_lock instead of access_lock 

Fanotify code has its own lock (access_lock) to protect a list of events
waiting for a response from userspace.

However this is somewhat awkward as the same list_head in the event is
protected by notification_lock if it is part of the notification queue
and by access_lock if it is part of the fanotify private queue which
makes it difficult for any reliable checks in the generic code.  So make
fanotify use the same lock - notification_lock - for protecting its
private event list.

Link: http://lkml.kernel.org/r/1473797711-14111-6-git-send-email-jack@suse.cz


Signed-off-by: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarLino Sanfilippo <LinoSanfilippo@gmx.de>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: Eric Paris <eparis@redhat.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c21dbe20

fs/notify/fanotify/fanotify_user.c

+5 −8
Original line number Diff line number Diff line
@@ -148,7 +148,7 @@ static struct fanotify_perm_event_info *dequeue_event( 
{

	struct fanotify_perm_event_info *event, *return_e = NULL;



	spin_lock(&group->fanotify_data.access_lock);

	spin_lock(&group->notification_lock);

	list_for_each_entry(event, &group->fanotify_data.access_list,

			    fae.fse.list) {

		if (event->fd != fd)
@@ -158,7 +158,7 @@ static struct fanotify_perm_event_info *dequeue_event( 
		return_e = event;

		break;

	}

	spin_unlock(&group->fanotify_data.access_lock);

	spin_unlock(&group->notification_lock);



	pr_debug("%s: found return_re=%p\n", __func__, return_e);
@@ -310,10 +310,10 @@ static ssize_t fanotify_read(struct file *file, char __user *buf, 
				wake_up(&group->fanotify_data.access_waitq);

				break;

			}

			spin_lock(&group->fanotify_data.access_lock);

			spin_lock(&group->notification_lock);

			list_add_tail(&kevent->list,

				      &group->fanotify_data.access_list);

			spin_unlock(&group->fanotify_data.access_lock);

			spin_unlock(&group->notification_lock);

#endif

		}

		buf += ret;
@@ -372,7 +372,7 @@ static int fanotify_release(struct inode *ignored, struct file *file) 
	 * Process all permission events on access_list and notification queue

	 * and simulate reply from userspace.

	 */

	spin_lock(&group->fanotify_data.access_lock);

	spin_lock(&group->notification_lock);

	list_for_each_entry_safe(event, next, &group->fanotify_data.access_list,

				 fae.fse.list) {

		pr_debug("%s: found group=%p event=%p\n", __func__, group,
@@ -381,14 +381,12 @@ static int fanotify_release(struct inode *ignored, struct file *file) 
		list_del_init(&event->fae.fse.list);

		event->response = FAN_ALLOW;

	}

	spin_unlock(&group->fanotify_data.access_lock);



	/*

	 * Destroy all non-permission events. For permission events just

	 * dequeue them and set the response. They will be freed once the

	 * response is consumed and fanotify_get_response() returns.

	 */

	spin_lock(&group->notification_lock);

	while (!fsnotify_notify_queue_is_empty(group)) {

		fsn_event = fsnotify_remove_first_event(group);

		if (!(fsn_event->mask & FAN_ALL_PERM_EVENTS)) {
@@ -768,7 +766,6 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags) 
		event_f_flags |= O_LARGEFILE;

	group->fanotify_data.f_flags = event_f_flags;

#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS

	spin_lock_init(&group->fanotify_data.access_lock);

	init_waitqueue_head(&group->fanotify_data.access_waitq);

	INIT_LIST_HEAD(&group->fanotify_data.access_list);

#endif

include/linux/fsnotify_backend.h

+0 −1
Original line number Diff line number Diff line
@@ -177,7 +177,6 @@ struct fsnotify_group { 
		struct fanotify_group_private_data {

#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS

			/* allows a group to block waiting for a userspace response */

			spinlock_t access_lock;

			struct list_head access_list;

			wait_queue_head_t access_waitq;

#endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */

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