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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 17:54:56 +0100
commit7761daa6a1599fa5479b8da367470f632a1927e0 (patch)
treef1ed23c310e76b1a78447268f9d16c153bb32721 /fs/notify
parent9cf90cef362d44b2f3fcdb7d0694849a6308b620 (diff)
downloadlinux-7761daa6a1599fa5479b8da367470f632a1927e0.tar.bz2
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 'fs/notify')
-rw-r--r--fs/notify/group.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/fs/notify/group.c b/fs/notify/group.c
index 32357534de18..b7a4b6a69efa 100644
--- a/fs/notify/group.c
+++ b/fs/notify/group.c
@@ -107,7 +107,7 @@ void fsnotify_destroy_group(struct fsnotify_group *group)
*/
void fsnotify_get_group(struct fsnotify_group *group)
{
- atomic_inc(&group->refcnt);
+ refcount_inc(&group->refcnt);
}
/*
@@ -115,7 +115,7 @@ void fsnotify_get_group(struct fsnotify_group *group)
*/
void fsnotify_put_group(struct fsnotify_group *group)
{
- if (atomic_dec_and_test(&group->refcnt))
+ if (refcount_dec_and_test(&group->refcnt))
fsnotify_final_destroy_group(group);
}
@@ -131,7 +131,7 @@ struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
return ERR_PTR(-ENOMEM);
/* set to 0 when there a no external references to this group */
- atomic_set(&group->refcnt, 1);
+ refcount_set(&group->refcnt, 1);
atomic_set(&group->num_marks, 0);
atomic_set(&group->user_waits, 0);