linux-kernel - [PATCH net] net: atm: fix use after free in lec

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Message-ID: <c751531d-4af4-42fe-affe-6104b34b791d@stanley.mountain>
Date: Fri, 14 Mar 2025 13:10:57 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Simon Horman <horms@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH net] net: atm: fix use after free in lec_send()

The ->send() operation frees skb so save the length before calling
->send() to avoid a use after free.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
 net/atm/lec.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/atm/lec.c b/net/atm/lec.c
index ffef658862db..a948dd47c3f3 100644
--- a/net/atm/lec.c
+++ b/net/atm/lec.c
@@ -181,6 +181,7 @@ static void
 lec_send(struct atm_vcc *vcc, struct sk_buff *skb)
 {
 	struct net_device *dev = skb->dev;
+	unsigned int len = skb->len;
 
 	ATM_SKB(skb)->vcc = vcc;
 	atm_account_tx(vcc, skb);
@@ -191,7 +192,7 @@ lec_send(struct atm_vcc *vcc, struct sk_buff *skb)
 	}
 
 	dev->stats.tx_packets++;
-	dev->stats.tx_bytes += skb->len;
+	dev->stats.tx_bytes += len;
 }
 
 static void lec_tx_timeout(struct net_device *dev, unsigned int txqueue)
-- 
2.47.2