[PATCH v1 2/3] net/af_packet: fix receive buffer overflow

[Xavier Guillaume <xavier.guillaume@ovhcloud.com>]

The receive path copies the entire incoming packet into a single
mbuf without verifying the packet fits. If the kernel interface
MTU is raised externally beyond the mbuf data room size, the
memcpy overflows the mbuf buffer.

Add a bounds check against the mbuf tailroom before copying.
Oversized packets are dropped and accounted for in the
rx_dropped_pkts counter, consistent with how the TX path
already drops oversized packets.

Fixes: 364e08f2bb ("af_packet: add PMD for AF_PACKET-based virtual devices")
Cc: stable@dpdk.org

Signed-off-by: Xavier Guillaume <xavier.guillaume@ovhcloud.com>
---
 drivers/net/af_packet/rte_eth_af_packet.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/net/af_packet/rte_eth_af_packet.c b/drivers/net/af_packet/rte_eth_af_packet.c
index bfa68297a6..b04987aaf7 100644
--- a/drivers/net/af_packet/rte_eth_af_packet.c
+++ b/drivers/net/af_packet/rte_eth_af_packet.c
@@ -154,6 +154,16 @@ eth_af_packet_rx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 			break;
 		}
 
+		/* drop packets that won't fit in the mbuf */
+		if (ppd->tp_snaplen > rte_pktmbuf_tailroom(mbuf)) {
+			rte_pktmbuf_free(mbuf);
+			ppd->tp_status = TP_STATUS_KERNEL;
+			if (++framenum >= framecount)
+				framenum = 0;
+			pkt_q->rx_dropped_pkts++;
+			continue;
+		}
+
 		/* packet will fit in the mbuf, go ahead and receive it */
 		rte_pktmbuf_pkt_len(mbuf) = rte_pktmbuf_data_len(mbuf) = ppd->tp_snaplen;
 		pbuf = (uint8_t *) ppd + ppd->tp_mac;
-- 
2.34.1