[dpdk-stable] [PATCH v3] mbuf: fix out-of-bounds access at dyn field register

[Xiaolong Ye <xiaolong.ye@intel.com>]

We should make sure off + size < sizeof(struct rte_mbuf) to avoid
possible out-of-bounds access of free_space array, there is no issue
currently due to the low bits of free_flags (which is adjacent to
free_space) are always set to 0. But we shouldn't rely on it since it's
fragile and layout of struct mbuf_dyn_shm may be changed in the future.
This patch adds boundary check explicitly to avoid potential risk of
out-of-bounds access.

Fixes: 4958ca3a443a ("mbuf: support dynamic fields and flags")
Cc: stable@dpdk.org

Signed-off-by: Xiaolong Ye <xiaolong.ye@intel.com>
---

V3: update subject as Olivier suggested

 lib/librte_mbuf/rte_mbuf_dyn.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/librte_mbuf/rte_mbuf_dyn.c b/lib/librte_mbuf/rte_mbuf_dyn.c
index d6931f847..9d6388cff 100644
--- a/lib/librte_mbuf/rte_mbuf_dyn.c
+++ b/lib/librte_mbuf/rte_mbuf_dyn.c
@@ -71,7 +71,8 @@ process_score(void)
 
 	for (off = 0; off < sizeof(struct rte_mbuf); off++) {
 		/* get the size of the free zone */
-		for (size = 0; shm->free_space[off + size]; size++)
+		for (size = 0; (off + size) < sizeof(struct rte_mbuf) &&
+			     shm->free_space[off + size]; size++)
 			;
 		if (size == 0)
 			continue;
-- 
2.17.1