[PATCH 6.1 055/131] net: refine debug info in skb_checksum_help()

Greg Kroah-Hartman
2023-10-16T08:56:40Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 26c29961b142444cd99361644c30fa1e9b3da6be ]

syzbot uses panic_on_warn.

This means that the skb_dump() I added in the blamed commit are
not even called.

Rewrite this so that we get the needed skb dump before syzbot crashes.

Fixes: eeee4b77dc52 ("net: add more debug info in skb_checksum_help()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20231006173355.2254983-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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 a2e3c6470ab3f..5374761f5af2c 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3274,15 +3274,19 @@ int skb_checksum_help(struct sk_buff *skb)

offset = skb_checksum_start_offset(skb);
ret = -EINVAL;
- if (WARN_ON_ONCE(offset >= skb_headlen(skb))) {
+ if (unlikely(offset >= skb_headlen(skb))) {
DO_ONCE_LITE(skb_dump, KERN_ERR, skb, false);
+ WARN_ONCE(true, "offset (%d) >= skb_headlen() (%u)\n",
+ offset, skb_headlen(skb));
goto out;
}
csum = skb_checksum(skb, offset, skb->len - offset, 0);

offset += skb->csum_offset;
- if (WARN_ON_ONCE(offset + sizeof(__sum16) > skb_headlen(skb))) {
+ if (unlikely(offset + sizeof(__sum16) > skb_headlen(skb))) {
DO_ONCE_LITE(skb_dump, KERN_ERR, skb, false);
+ WARN_ONCE(true, "offset+2 (%zu) > skb_headlen() (%u)\n",
+ offset + sizeof(__sum16), skb_headlen(skb));
goto out;
}
ret = skb_ensure_writable(skb, offset + sizeof(__sum16));
--
2.40.1