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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 13:48:00 -0500
commit0896cade1224f167296c786043e9bdc0ca63d392 (patch)
treec216743ad8977e9423909ca6669d8e58ea2764b0 /fs/nfs/cache_lib.h
parent81a090b9975b89ca15e71d0bca945358f6fe7696 (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/nfs/cache_lib.h')
-rw-r--r--fs/nfs/cache_lib.h2
1 files changed, 1 insertions, 1 deletions
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);