netdev - [PATCH v2 net] net: hsr: Fix potential use-after-free

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Date:   Fri, 25 Nov 2022 15:57:24 +0800
From:   YueHaibing <yuehaibing@...wei.com>
To:     <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
        <pabeni@...hat.com>, <arvid.brodin@...en.se>
CC:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        YueHaibing <yuehaibing@...wei.com>
Subject: [PATCH v2 net] net: hsr: Fix potential use-after-free

The skb is delivered to netif_rx() which may free it, after calling this,
dereferencing skb may trigger use-after-free.

Fixes: f421436a591d ("net/hsr: Add support for the High-availability Seamless Redundancy protocol (HSRv0)")
Signed-off-by: YueHaibing <yuehaibing@...wei.com>
---
v2: correct Fixes tag
---
 net/hsr/hsr_forward.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/hsr/hsr_forward.c b/net/hsr/hsr_forward.c
index a50429a62f74..56bb27d67a2e 100644
--- a/net/hsr/hsr_forward.c
+++ b/net/hsr/hsr_forward.c
@@ -351,17 +351,18 @@ static void hsr_deliver_master(struct sk_buff *skb, struct net_device *dev,
 			       struct hsr_node *node_src)
 {
 	bool was_multicast_frame;
-	int res;
+	int res, recv_len;
 
 	was_multicast_frame = (skb->pkt_type == PACKET_MULTICAST);
 	hsr_addr_subst_source(node_src, skb);
 	skb_pull(skb, ETH_HLEN);
+	recv_len = skb->len;
 	res = netif_rx(skb);
 	if (res == NET_RX_DROP) {
 		dev->stats.rx_dropped++;
 	} else {
 		dev->stats.rx_packets++;
-		dev->stats.rx_bytes += skb->len;
+		dev->stats.rx_bytes += recv_len;
 		if (was_multicast_frame)
 			dev->stats.multicast++;
 	}
-- 
2.17.1