[PATCH 3.18 28/58] net: avoid skb_warn_bad_offload on IS_ERR

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Willem de Bruijn <willemb@google.com>

commit 8d74e9f88d65af8bb2e095aff506aa6eac755ada upstream.

skb_warn_bad_offload warns when packets enter the GSO stack that
require skb_checksum_help or vice versa. Do not warn on arbitrary
bad packets. Packet sockets can craft many. Syzkaller was able to
demonstrate another one with eth_type games.

In particular, suppress the warning when segmentation returns an
error, which is for reasons other than checksum offload.

See also commit 36c92474498a ("net: WARN if skb_checksum_help() is
called on skb requiring segmentation") for context on this warning.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/core/dev.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2478,7 +2478,7 @@ struct sk_buff *__skb_gso_segment(struct
 
 	segs = skb_mac_gso_segment(skb, features);
 
-	if (unlikely(skb_needs_check(skb, tx_path)))
+	if (unlikely(skb_needs_check(skb, tx_path) && !IS_ERR(segs)))
 		skb_warn_bad_offload(skb);
 
 	return segs;