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authorElena Reshetova <elena.reshetova@intel.com>2017-10-20 12:53:37 +0300
committerAnna Schumaker <Anna.Schumaker@Netapp.com>2017-11-17 13:48:01 -0500
commit2f62b5aa4814be2c511553fd6afb4d35b6c2503b (patch)
treecf402bfd8d23ea6dbf02e67a45edd9e49a8822af /include/linux/nfs_fs.h
parent194bc1f48100a3b6fbd50d7a2218b594f0c564b6 (diff)
fs, nfs: convert nfs_lock_context.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_lock_context.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 'include/linux/nfs_fs.h')
-rw-r--r--include/linux/nfs_fs.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 453f491a5fda..e6706913e6c2 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -22,6 +22,7 @@
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/rbtree.h>
+#include <linux/refcount.h>
#include <linux/rwsem.h>
#include <linux/wait.h>
@@ -55,7 +56,7 @@ struct nfs_access_entry {
};
struct nfs_lock_context {
- atomic_t count;
+ refcount_t count;
struct list_head list;
struct nfs_open_context *open_context;
fl_owner_t lockowner;