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authorElena Reshetova <elena.reshetova@intel.com>2017-10-20 12:53:35 +0300
committerAnna Schumaker <Anna.Schumaker@Netapp.com>2017-11-17 21:48:00 +0300
commit0896cade1224f167296c786043e9bdc0ca63d392 (patch)
treec216743ad8977e9423909ca6669d8e58ea2764b0 /fs/nfs/cache_lib.c
parent81a090b9975b89ca15e71d0bca945358f6fe7696 (diff)
downloadlinux-0896cade1224f167296c786043e9bdc0ca63d392.tar.xz
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/nfs/cache_lib.c')
-rw-r--r--fs/nfs/cache_lib.c6
1 files changed, 3 insertions, 3 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;