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| author | Jan Kara <jack@suse.cz> | 2014-08-06 16:03:28 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-08-06 18:01:12 -0700 |
| commit | 5838d4442bd5971687b72221736222637e03140d (patch) | |
| tree | e639967a7baf1b1c6a0d1b5e0babc8083c7faad4 /fs/notify/fanotify | |
| parent | 8ba8fa917093510cdcb4ec8ff8b9603e1b525658 (diff) | |
| download | linux-5838d4442bd5971687b72221736222637e03140d.tar.gz linux-5838d4442bd5971687b72221736222637e03140d.tar.bz2 linux-5838d4442bd5971687b72221736222637e03140d.zip | |
fanotify: fix double free of pending permission events
Commit 85816794240b ("fanotify: Fix use after free for permission
events") introduced a double free issue for permission events which are
pending in group's notification queue while group is being destroyed.
These events are freed from fanotify_handle_event() but they are not
removed from groups notification queue and thus they get freed again
from fsnotify_flush_notify().
Fix the problem by removing permission events from notification queue
before freeing them if we skip processing access response. Also expand
comments in fanotify_release() to explain group shutdown in detail.
Fixes: 85816794240b9659e66e4d9b0df7c6e814e5f603
Signed-off-by: Jan Kara <jack@suse.cz>
Reported-by: Douglas Leeder <douglas.leeder@sophos.com>
Tested-by: Douglas Leeder <douglas.leeder@sophos.com>
Reported-by: Heinrich Schuchard <xypron.glpk@gmx.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/notify/fanotify')
| -rw-r--r-- | fs/notify/fanotify/fanotify.c | 9 | ||||
| -rw-r--r-- | fs/notify/fanotify/fanotify_user.c | 12 |
2 files changed, 20 insertions, 1 deletions
diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c index fdeb36b70c65..30d3addfad75 100644 --- a/fs/notify/fanotify/fanotify.c +++ b/fs/notify/fanotify/fanotify.c @@ -70,8 +70,15 @@ static int fanotify_get_response(struct fsnotify_group *group, wait_event(group->fanotify_data.access_waitq, event->response || atomic_read(&group->fanotify_data.bypass_perm)); - if (!event->response) /* bypass_perm set */ + if (!event->response) { /* bypass_perm set */ + /* + * Event was canceled because group is being destroyed. Remove + * it from group's event list because we are responsible for + * freeing the permission event. + */ + fsnotify_remove_event(group, &event->fae.fse); return 0; + } /* userspace responded, convert to something usable */ switch (event->response) { diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c index fbf2210823ab..b13992a41bd9 100644 --- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -359,6 +359,11 @@ static int fanotify_release(struct inode *ignored, struct file *file) #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS struct fanotify_perm_event_info *event, *next; + /* + * There may be still new events arriving in the notification queue + * but since userspace cannot use fanotify fd anymore, no event can + * enter or leave access_list by now. + */ spin_lock(&group->fanotify_data.access_lock); atomic_inc(&group->fanotify_data.bypass_perm); @@ -373,6 +378,13 @@ static int fanotify_release(struct inode *ignored, struct file *file) } spin_unlock(&group->fanotify_data.access_lock); + /* + * Since bypass_perm is set, newly queued events will not wait for + * access response. Wake up the already sleeping ones now. + * synchronize_srcu() in fsnotify_destroy_group() will wait for all + * processes sleeping in fanotify_handle_event() waiting for access + * response and thus also for all permission events to be freed. + */ wake_up(&group->fanotify_data.access_waitq); #endif |