netdev - [PATCH AUTOSEL 5.4 34/55] net: remove two BUG() from skb_checksum

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Message-Id: <20220530134701.1935933-34-sashal@kernel.org>
Date:   Mon, 30 May 2022 09:46:40 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Eric Dumazet <edumazet@...gle.com>,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>, kuba@...nel.org,
        pabeni@...hat.com, bigeasy@...utronix.de, imagedong@...cent.com,
        petrm@...dia.com, memxor@...il.com, arnd@...db.de,
        netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 34/55] net: remove two BUG() from skb_checksum_help()

From: Eric Dumazet <edumazet@...gle.com>

[ Upstream commit d7ea0d9df2a6265b2b180d17ebc64b38105968fc ]

I have a syzbot report that managed to get a crash in skb_checksum_help()

If syzbot can trigger these BUG(), it makes sense to replace
them with more friendly WARN_ON_ONCE() since skb_checksum_help()
can instead return an error code.

Note that syzbot will still crash there, until real bug is fixed.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/core/dev.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index a03036456221..8fd0a0591e89 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2857,11 +2857,15 @@ int skb_checksum_help(struct sk_buff *skb)
 	}
 
 	offset = skb_checksum_start_offset(skb);
-	BUG_ON(offset >= skb_headlen(skb));
+	ret = -EINVAL;
+	if (WARN_ON_ONCE(offset >= skb_headlen(skb)))
+		goto out;
+
 	csum = skb_checksum(skb, offset, skb->len - offset, 0);
 
 	offset += skb->csum_offset;
-	BUG_ON(offset + sizeof(__sum16) > skb_headlen(skb));
+	if (WARN_ON_ONCE(offset + sizeof(__sum16) > skb_headlen(skb)))
+		goto out;
 
 	if (skb_cloned(skb) &&
 	    !skb_clone_writable(skb, offset + sizeof(__sum16))) {
-- 
2.35.1