[dpdk-dev] [PATCH v2] net/mlx5: Fix possible NULL deref in RX path

[Sagi Grimberg <sagi@grimberg.me>]

The user is allowed to call ->rx_pkt_burst() even without free
mbufs in the pool. In this scenario we'll fail allocating a rep mbuf
on the first iteration (where pkt is still NULL). This would cause us
to deref a NULL pkt (reset refcount and free).

Fix this by checking the pkt before freeing it.

Fixes: a1bdb71a32da ("net/mlx5: fix crash in Rx")
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
---
Changes from v1:
- check pkt only once in case we failed to allocate a buffer

 drivers/net/mlx5/mlx5_rxtx.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
index fce3381ae87a..37573668e43e 100644
--- a/drivers/net/mlx5/mlx5_rxtx.c
+++ b/drivers/net/mlx5/mlx5_rxtx.c
@@ -1572,6 +1572,14 @@ mlx5_rx_burst(void *dpdk_rxq, struct rte_mbuf **pkts, uint16_t pkts_n)
 		rte_prefetch0(wqe);
 		rep = rte_mbuf_raw_alloc(rxq->mp);
 		if (unlikely(rep == NULL)) {
+			++rxq->stats.rx_nombuf;
+			if (!pkt) {
+				/*
+				 * no buffers before we even started,
+				 * bail out silently.
+				 */
+				break;
+			}
 			while (pkt != seg) {
 				assert(pkt != (*rxq->elts)[idx]);
 				seg = NEXT(pkt);
@@ -1579,7 +1587,6 @@ mlx5_rx_burst(void *dpdk_rxq, struct rte_mbuf **pkts, uint16_t pkts_n)
 				__rte_mbuf_raw_free(pkt);
 				pkt = seg;
 			}
-			++rxq->stats.rx_nombuf;
 			break;
 		}
 		if (!pkt) {
-- 
1.9.1