net, xfrm: convert sec_path.refcnt from atomic_t to refcount_t

refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index e1bd1de..c0916ab 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -1030,7 +1030,7 @@
 };
 
 struct sec_path {
-	atomic_t		refcnt;
+	refcount_t		refcnt;
 	int			len;
 	int			olen;
 
@@ -1051,7 +1051,7 @@
 secpath_get(struct sec_path *sp)
 {
 	if (sp)
-		atomic_inc(&sp->refcnt);
+		refcount_inc(&sp->refcnt);
 	return sp;
 }
 
@@ -1060,7 +1060,7 @@
 static inline void
 secpath_put(struct sec_path *sp)
 {
-	if (sp && atomic_dec_and_test(&sp->refcnt))
+	if (sp && refcount_dec_and_test(&sp->refcnt))
 		__secpath_destroy(sp);
 }