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authorElena Reshetova <elena.reshetova@intel.com>2017-10-20 13:26:01 +0300
committerJan Kara <jack@suse.cz>2017-10-31 19:54:56 +0300
commit7761daa6a1599fa5479b8da367470f632a1927e0 (patch)
treef1ed23c310e76b1a78447268f9d16c153bb32721 /include/linux/fsnotify_backend.h
parent9cf90cef362d44b2f3fcdb7d0694849a6308b620 (diff)
downloadlinux-7761daa6a1599fa5479b8da367470f632a1927e0.tar.xz
fsnotify: convert fsnotify_group.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_group.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 'include/linux/fsnotify_backend.h')
-rw-r--r--include/linux/fsnotify_backend.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index c6c69318752b..20a57bac38f2 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -17,6 +17,7 @@
#include <linux/types.h>
#include <linux/atomic.h>
#include <linux/user_namespace.h>
+#include <linux/refcount.h>
/*
* IN_* from inotfy.h lines up EXACTLY with FS_*, this is so we can easily
@@ -135,7 +136,7 @@ struct fsnotify_group {
* inotify_init() and the refcnt will hit 0 only when that fd has been
* closed.
*/
- atomic_t refcnt; /* things with interest in this group */
+ refcount_t refcnt; /* things with interest in this group */
const struct fsnotify_ops *ops; /* how this group handles things */