[PATCH 7.1 080/271] net/sched: sch_cake: drop WARN_ON(1) for malformed packets in ACK filter

Greg Kroah-Hartman <[email protected]>
Newsgroups dev.linux.lists.patches,org.kernel.vger.stable
Message-ID <[email protected]>
7.1-stable review patch.  If anyone has any objections, please let me know.

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

From: Toke Høiland-Jørgensen <[email protected]>

[ Upstream commit 2a33516f9ef59ad11844d4fc152f889449b5daf3 ]

The sch_cake ACK filter parses packets to find the TCP header and filter
duplicated ACKs if the flow is backlogged. The parsing code contains a
WARN_ON(1) which can be triggered by a malformed IP header in certain
cases. Depending on the system configuration, this leads either to
either spamming dmesg with warnings, or a panic if panic_on_warn is set.

The code already correctly skips the offending packet in the branch that
triggers the warning, so the WARN_ON itself doesn't really serve any
purpose. So just drop it altogether to avoid the inconvenient side
effects.

Fixes: 8b7138814f29 ("sch_cake: Add optional ACK filter")
Reported-by: Zhiling Zou <[email protected]>
Reported-by: Ren Wei <[email protected]>
Signed-off-by: Toke Høiland-Jørgensen <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
---
 net/sched/sch_cake.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/net/sched/sch_cake.c b/net/sched/sch_cake.c
index 8965fe252471c..755c42c32bcf3 100644
--- a/net/sched/sch_cake.c
+++ b/net/sched/sch_cake.c
@@ -1287,7 +1287,6 @@ static struct sk_buff *cake_ack_filter(struct cake_sched_data *q,
 
 			seglen = ipv6_payload_len(skb, ipv6h_check);
 		} else {
-			WARN_ON(1);  /* shouldn't happen */
 			continue;
 		}
 
-- 
2.53.0
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