diff options
author | Elena Reshetova | 2017-10-20 12:53:35 +0300 |
---|---|---|
committer | Anna Schumaker | 2017-11-17 13:48:00 -0500 |
commit | 0896cade1224f167296c786043e9bdc0ca63d392 (patch) | |
tree | c216743ad8977e9423909ca6669d8e58ea2764b0 /fs | |
parent | 81a090b9975b89ca15e71d0bca945358f6fe7696 (diff) |
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 <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: Anna Schumaker <Anna.Schumaker@Netapp.com>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/nfs/cache_lib.c | 6 | ||||
-rw-r--r-- | fs/nfs/cache_lib.h | 2 |
2 files changed, 4 insertions, 4 deletions
diff --git a/fs/nfs/cache_lib.c b/fs/nfs/cache_lib.c index 2ae676f93e6b..6167f13025d7 100644 --- a/fs/nfs/cache_lib.c +++ b/fs/nfs/cache_lib.c @@ -66,7 +66,7 @@ out: */ void nfs_cache_defer_req_put(struct nfs_cache_defer_req *dreq) { - if (atomic_dec_and_test(&dreq->count)) + if (refcount_dec_and_test(&dreq->count)) kfree(dreq); } @@ -86,7 +86,7 @@ static struct cache_deferred_req *nfs_dns_cache_defer(struct cache_req *req) dreq = container_of(req, struct nfs_cache_defer_req, req); dreq->deferred_req.revisit = nfs_dns_cache_revisit; - atomic_inc(&dreq->count); + refcount_inc(&dreq->count); return &dreq->deferred_req; } @@ -98,7 +98,7 @@ struct nfs_cache_defer_req *nfs_cache_defer_req_alloc(void) dreq = kzalloc(sizeof(*dreq), GFP_KERNEL); if (dreq) { init_completion(&dreq->completion); - atomic_set(&dreq->count, 1); + refcount_set(&dreq->count, 1); dreq->req.defer = nfs_dns_cache_defer; } return dreq; 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); |