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

Sasha Levin
2022-05-30T14:44:47Z

From: Eric Dumazet <edumazet@google.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@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.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