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authorElena Reshetova <elena.reshetova@intel.com>2017-10-20 12:53:28 +0300
committerJ. Bruce Fields <bfields@redhat.com>2017-11-08 00:43:58 +0300
commita15dfcd529ab43265e70ec32d3b9d2286872d412 (patch)
tree798c5bbb1198cc1135fed233bc315806918cc85d /fs/nfsd/state.h
parentdc3033e16c59a2c4e62b31341258a5786cbcee56 (diff)
downloadlinux-a15dfcd529ab43265e70ec32d3b9d2286872d412.tar.xz
fs, nfsd: convert nfs4_stid.sc_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 nfs4_stid.sc_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: J. Bruce Fields <bfields@redhat.com>
Diffstat (limited to 'fs/nfsd/state.h')
-rw-r--r--fs/nfsd/state.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index 86aa92d200e1..c259271c35a4 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -36,6 +36,7 @@
#define _NFSD4_STATE_H
#include <linux/idr.h>
+#include <linux/refcount.h>
#include <linux/sunrpc/svc_xprt.h>
#include "nfsfh.h"
@@ -83,7 +84,7 @@ struct nfsd4_callback_ops {
* fields that are of general use to any stateid.
*/
struct nfs4_stid {
- atomic_t sc_count;
+ refcount_t sc_count;
#define NFS4_OPEN_STID 1
#define NFS4_LOCK_STID 2
#define NFS4_DELEG_STID 4