diff options
| author | Elena Reshetova <elena.reshetova@intel.com> | 2017-10-20 13:26:02 +0300 |
|---|---|---|
| committer | Jan Kara <jack@suse.cz> | 2017-10-31 17:54:56 +0100 |
| commit | ab97f87325e28b7ef7717e6cb62e8da14a7176e1 (patch) | |
| tree | 7ce8f0a747efaff1907f3774479dcbc2f4762c48 /fs/notify/inotify | |
| parent | 6685df31255493c3f0e9e0b8bf885e4c9762fc5d (diff) | |
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/inotify')
| -rw-r--r-- | fs/notify/inotify/inotify_user.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c index 7cc7d3fb1862..d3c20e0bb046 100644 --- a/fs/notify/inotify/inotify_user.c +++ b/fs/notify/inotify/inotify_user.c @@ -376,7 +376,7 @@ static struct inotify_inode_mark *inotify_idr_find_locked(struct fsnotify_group fsnotify_get_mark(fsn_mark); /* One ref for being in the idr, one ref we just took */ - BUG_ON(atomic_read(&fsn_mark->refcnt) < 2); + BUG_ON(refcount_read(&fsn_mark->refcnt) < 2); } return i_mark; @@ -446,7 +446,7 @@ static void inotify_remove_from_idr(struct fsnotify_group *group, * One ref for being in the idr * one ref grabbed by inotify_idr_find */ - if (unlikely(atomic_read(&i_mark->fsn_mark.refcnt) < 2)) { + if (unlikely(refcount_read(&i_mark->fsn_mark.refcnt) < 2)) { printk(KERN_ERR "%s: i_mark=%p i_mark->wd=%d i_mark->group=%p\n", __func__, i_mark, i_mark->wd, i_mark->fsn_mark.group); /* we can't really recover with bad ref cnting.. */ |