From: Lino Sanfilippo <LinoSanfilippo@gmx.de>
To: Jan Kara <jack@suse.cz>, Andrew Morton <akpm@linux-foundation.org>
Cc: linux-fsdevel@vger.kernel.org,
Miklos Szeredi <mszeredi@redhat.com>,
Eric Paris <eparis@redhat.com>, Al Viro <viro@ZenIV.linux.org.uk>
Subject: Re: [PATCH 3/6] fsnotify: Drop notification_mutex before destroying event
Date: Wed, 14 Sep 2016 19:11:34 +0200 [thread overview]
Message-ID: <c1f673f1-bdea-f736-9c63-955924cb661d@gmx.de> (raw)
In-Reply-To: <1473797711-14111-4-git-send-email-jack@suse.cz>
On 13.09.2016 22:15, Jan Kara wrote:
> 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);
> }
>
Reviewed-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
next prev parent reply other threads:[~2016-09-14 17:11 UTC|newest]
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 ` [PATCH 3/6] fsnotify: Drop notification_mutex before destroying event Jan Kara
2016-09-14 17:11 ` Lino Sanfilippo [this message]
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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