From: Jan Kara <jack@suse.cz> To: Andrew Morton <akpm@linux-foundation.org> Cc: linux-fsdevel@vger.kernel.org, Miklos Szeredi <mszeredi@redhat.com>, Lino Sanfilippo <LinoSanfilippo@gmx.de>, Eric Paris <eparis@redhat.com>, Al Viro <viro@ZenIV.linux.org.uk>, Jan Kara <jack@suse.cz> Subject: [PATCH 3/6] fsnotify: Drop notification_mutex before destroying event Date: Tue, 13 Sep 2016 22:15:08 +0200 Message-ID: <1473797711-14111-4-git-send-email-jack@suse.cz> (raw) In-Reply-To: <1473797711-14111-1-git-send-email-jack@suse.cz> fsnotify_flush_notify() and fanotify_release() destroy notification event while holding notification_mutex. Destruction of fanotify event includes a path_put() call which may end up calling into a filesystem to delete an inode if we happen to be the last holders of dentry reference which happens to be the last holder of inode reference. That may violate lock ordering for some filesystems since notification_mutex is also acquired e. g. during write when generating fanotify event. Also this is the only thing that forces notification_mutex to be a sleeping lock. So drop notification_mutex before destroying a notification event. Signed-off-by: Jan Kara <jack@suse.cz> --- fs/notify/fanotify/fanotify_user.c | 6 ++++-- fs/notify/notification.c | 2 ++ 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c index a64313868d3a..46d135c4988f 100644 --- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -390,9 +390,11 @@ static int fanotify_release(struct inode *ignored, struct file *file) mutex_lock(&group->notification_mutex); while (!fsnotify_notify_queue_is_empty(group)) { fsn_event = fsnotify_remove_first_event(group); - if (!(fsn_event->mask & FAN_ALL_PERM_EVENTS)) + if (!(fsn_event->mask & FAN_ALL_PERM_EVENTS)) { + mutex_unlock(&group->notification_mutex); fsnotify_destroy_event(group, fsn_event); - else + mutex_lock(&group->notification_mutex); + } else FANOTIFY_PE(fsn_event)->response = FAN_ALLOW; } mutex_unlock(&group->notification_mutex); diff --git a/fs/notify/notification.c b/fs/notify/notification.c index e455e83ceeeb..7d563dea52a4 100644 --- a/fs/notify/notification.c +++ b/fs/notify/notification.c @@ -178,7 +178,9 @@ void fsnotify_flush_notify(struct fsnotify_group *group) mutex_lock(&group->notification_mutex); while (!fsnotify_notify_queue_is_empty(group)) { event = fsnotify_remove_first_event(group); + mutex_unlock(&group->notification_mutex); fsnotify_destroy_event(group, event); + mutex_lock(&group->notification_mutex); } mutex_unlock(&group->notification_mutex); } -- 2.6.6
next prev parent reply index Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-09-13 20:15 [PATCH 0/6 v2] fsnotify: Fix list corruption for permission events Jan Kara 2016-09-13 20:15 ` [PATCH 1/6] fsnotify: Add a way to stop queueing events on group shutdown Jan Kara 2016-09-13 20:15 ` [PATCH 2/6] fanotify: Fix list corruption in fanotify_get_response() Jan Kara 2016-09-13 20:15 ` Jan Kara [this message] 2016-09-14 17:11 ` [PATCH 3/6] fsnotify: Drop notification_mutex before destroying event Lino Sanfilippo 2016-09-13 20:15 ` [PATCH 4/6] fsnotify: Convert notification_mutex to a spinlock Jan Kara 2016-09-14 17:13 ` Lino Sanfilippo 2016-09-13 20:15 ` [PATCH 5/6] fanotify: Use notification_lock instead of access_lock Jan Kara 2016-09-14 17:14 ` Lino Sanfilippo 2016-09-13 20:15 ` [PATCH 6/6] fanotify: Fix possible false warning when freeing events Jan Kara 2016-09-14 17:14 ` Lino Sanfilippo
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