diff options
author | Elena Reshetova <elena.reshetova@intel.com> | 2017-10-20 12:26:02 +0200 |
---|---|---|
committer | Jan Kara <jack@suse.cz> | 2017-10-31 17:54:56 +0100 |
commit | ab97f87325e28b7ef7717e6cb62e8da14a7176e1 (patch) | |
tree | 7ce8f0a747efaff1907f3774479dcbc2f4762c48 /fs/notify/mark.c | |
parent | fanotify: clean up CONFIG_FANOTIFY_ACCESS_PERMISSIONS ifdefs (diff) | |
download | linux-ab97f87325e28b7ef7717e6cb62e8da14a7176e1.tar.xz linux-ab97f87325e28b7ef7717e6cb62e8da14a7176e1.zip |
fsnotify: convert fsnotify_mark.refcnt from atomic_t to refcount_t
atomic_t variables are currently used to implement reference
counters with the following properties:
- counter is initialized to 1 using atomic_set()
- a resource is freed upon counter reaching zero
- once counter reaches zero, its further
increments aren't allowed
- counter schema uses basic atomic operations
(set, inc, inc_not_zero, dec_and_test, etc.)
Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.
The variable fsnotify_mark.refcnt is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'fs/notify/mark.c')
-rw-r--r-- | fs/notify/mark.c | 14 |
1 files changed, 7 insertions, 7 deletions
diff --git a/fs/notify/mark.c b/fs/notify/mark.c index f3a32ea15b49..e9191b416434 100644 --- a/fs/notify/mark.c +++ b/fs/notify/mark.c @@ -105,8 +105,8 @@ static DECLARE_WORK(connector_reaper_work, fsnotify_connector_destroy_workfn); void fsnotify_get_mark(struct fsnotify_mark *mark) { - WARN_ON_ONCE(!atomic_read(&mark->refcnt)); - atomic_inc(&mark->refcnt); + WARN_ON_ONCE(!refcount_read(&mark->refcnt)); + refcount_inc(&mark->refcnt); } static void __fsnotify_recalc_mask(struct fsnotify_mark_connector *conn) @@ -201,7 +201,7 @@ void fsnotify_put_mark(struct fsnotify_mark *mark) /* Catch marks that were actually never attached to object */ if (!mark->connector) { - if (atomic_dec_and_test(&mark->refcnt)) + if (refcount_dec_and_test(&mark->refcnt)) fsnotify_final_mark_destroy(mark); return; } @@ -210,7 +210,7 @@ void fsnotify_put_mark(struct fsnotify_mark *mark) * We have to be careful so that traversals of obj_list under lock can * safely grab mark reference. */ - if (!atomic_dec_and_lock(&mark->refcnt, &mark->connector->lock)) + if (!refcount_dec_and_lock(&mark->refcnt, &mark->connector->lock)) return; conn = mark->connector; @@ -258,7 +258,7 @@ static bool fsnotify_get_mark_safe(struct fsnotify_mark *mark) if (!mark) return true; - if (atomic_inc_not_zero(&mark->refcnt)) { + if (refcount_inc_not_zero(&mark->refcnt)) { spin_lock(&mark->lock); if (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED) { /* mark is attached, group is still alive then */ @@ -335,7 +335,7 @@ void fsnotify_detach_mark(struct fsnotify_mark *mark) WARN_ON_ONCE(!mutex_is_locked(&group->mark_mutex)); WARN_ON_ONCE(!srcu_read_lock_held(&fsnotify_mark_srcu) && - atomic_read(&mark->refcnt) < 1 + + refcount_read(&mark->refcnt) < 1 + !!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)); spin_lock(&mark->lock); @@ -737,7 +737,7 @@ void fsnotify_init_mark(struct fsnotify_mark *mark, { memset(mark, 0, sizeof(*mark)); spin_lock_init(&mark->lock); - atomic_set(&mark->refcnt, 1); + refcount_set(&mark->refcnt, 1); fsnotify_get_group(group); mark->group = group; } |