From 0896cade1224f167296c786043e9bdc0ca63d392 Mon Sep 17 00:00:00 2001 From: Elena Reshetova Date: Fri, 20 Oct 2017 12:53:35 +0300 Subject: fs, nfs: convert nfs_cache_defer_req.count 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 nfs_cache_defer_req.count is used as pure reference counter. Convert it to refcount_t and fix up the operations. Suggested-by: Kees Cook Reviewed-by: David Windsor Reviewed-by: Hans Liljestrand Signed-off-by: Elena Reshetova Signed-off-by: Anna Schumaker --- fs/nfs/cache_lib.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/nfs/cache_lib.h') diff --git a/fs/nfs/cache_lib.h b/fs/nfs/cache_lib.h index 4116d2c3f52f..02b378c2eeef 100644 --- a/fs/nfs/cache_lib.h +++ b/fs/nfs/cache_lib.h @@ -15,7 +15,7 @@ struct nfs_cache_defer_req { struct cache_req req; struct cache_deferred_req deferred_req; struct completion completion; - atomic_t count; + refcount_t count; }; extern int nfs_cache_upcall(struct cache_detail *cd, char *entry_name); -- cgit v1.2.3