net/mlx5: fix possible NULL dereference in Rx path

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>
Acked-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>

diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
index fce3381..3757366 100644 (file)
--- 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) {