ceph: fix bounds check in ceph_decode_need and ceph_encode_need

Given a large n, the bounds check (*p + n > end) can be bypassed due to pointer wraparound. A safer check is (n > end - *p). [[email protected]: inverted test and renamed ceph_has_room()] Signed-off-by: Xi Wang <[email protected]> Reviewed-by: Alex Elder <[email protected]>
pllopis · May 14, 2012 · 76aa542 · 76aa542
1 parent 065a68f
commit 76aa542
Showing 1 changed file with 7 additions and 2 deletions.
diff --git a/include/linux/ceph/decode.h b/include/linux/ceph/decode.h
@@ -45,9 +45,14 @@ static inline void ceph_decode_copy(void **p, void *pv, size_t n)
 /*
  * bounds check input.
  */
+static inline int ceph_has_room(void **p, void *end, size_t n)
+{
+	return end >= *p && n <= end - *p;
+}
+
 #define ceph_decode_need(p, end, n, bad)		\
 	do {						\
-		if (unlikely(*(p) + (n) > (end))) 	\
+		if (!likely(ceph_has_room(p, end, n)))	\
 			goto bad;			\
 	} while (0)
 
@@ -166,7 +171,7 @@ static inline void ceph_encode_string(void **p, void *end,
 
 #define ceph_encode_need(p, end, n, bad)		\
 	do {						\
-		if (unlikely(*(p) + (n) > (end))) 	\
+		if (!likely(ceph_has_room(p, end, n)))	\
 			goto bad;			\
 	} while (0)