[PATCH 5.15.y] net: mana: Validate the packet length reported by the NIC

[Sasha Levin <sashal@kernel.org>]

From: Dexuan Cui <decui@microsoft.com>

[ Upstream commit 2e2a83b4998af4384e677d3b2ac08565274279bf ]

Validate the packet length reported in the RX CQE before passing it
to skb processing. The CQE is supplied by the NIC device and should
not be blindly trusted.

Cc: stable@vger.kernel.org
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Fixes: ca9c54d2d6a5 ("net: mana: Add a driver for Microsoft Azure Network Adapter (MANA)")
Link: https://patch.msgid.link/20260702041237.617719-2-decui@microsoft.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/ethernet/microsoft/mana/mana_en.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index 6a8ed54f6040ab..27c93d6b9de464 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
@@ -1021,6 +1021,19 @@ static void mana_process_rx_cqe(struct mana_rxq *rxq, struct mana_cq *cq,
 	rxbuf_oob = &rxq->rx_oobs[curr];
 	WARN_ON_ONCE(rxbuf_oob->wqe_inf.wqe_size_in_bu != 1);
 
+	if (unlikely(pktlen > rxq->datasize)) {
+		/* Increase it even if mana_rx_skb() isn't called. */
+		rxq->rx_cq.work_done++;
+
+		++ndev->stats.rx_dropped;
+		netdev_warn_once(ndev,
+				 "Dropped oversized RX packet: len=%u, datasize=%u\n",
+				 pktlen, rxq->datasize);
+
+		/* Reuse the RX buffer since rxbuf_oob is unchanged. */
+		goto drop;
+	}
+
 	new_page = alloc_page(GFP_ATOMIC);
 
 	if (new_page) {
-- 
2.53.0