diff options
author | Jan Kara <jack@suse.cz> | 2014-08-07 01:03:28 +0200 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-08-07 03:01:12 +0200 |
commit | 5838d4442bd5971687b72221736222637e03140d (patch) | |
tree | e639967a7baf1b1c6a0d1b5e0babc8083c7faad4 /fs | |
parent | fsnotify: rename event handling functions (diff) | |
download | linux-5838d4442bd5971687b72221736222637e03140d.tar.xz 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')
-rw-r--r-- | fs/notify/fanotify/fanotify.c | 9 | ||||
-rw-r--r-- | fs/notify/fanotify/fanotify_user.c | 12 | ||||
-rw-r--r-- | fs/notify/notification.c | 18 |
3 files changed, 37 insertions, 2 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 diff --git a/fs/notify/notification.c b/fs/notify/notification.c index 1d394220acbe..a95d8e037aeb 100644 --- a/fs/notify/notification.c +++ b/fs/notify/notification.c @@ -73,7 +73,8 @@ void fsnotify_destroy_event(struct fsnotify_group *group, /* Overflow events are per-group and we don't want to free them */ if (!event || event->mask == FS_Q_OVERFLOW) return; - + /* If the event is still queued, we have a problem... */ + WARN_ON(!list_empty(&event->list)); group->ops->free_event(event); } @@ -125,6 +126,21 @@ queue: } /* + * Remove @event from group's notification queue. It is the responsibility of + * the caller to destroy the event. + */ +void fsnotify_remove_event(struct fsnotify_group *group, + struct fsnotify_event *event) +{ + mutex_lock(&group->notification_mutex); + if (!list_empty(&event->list)) { + list_del_init(&event->list); + group->q_len--; + } + mutex_unlock(&group->notification_mutex); +} + +/* * Remove and return the first event from the notification list. It is the * responsibility of the caller to destroy the obtained event */ |