net_sched: sch_sfq: fix a potential crash on gso_skb handling
[ Upstream commit 82ffbe7776d0ac084031f114167712269bf3d832 ] SFQ has an assumption of always being able to queue at least one packet. However, after the blamed commit, sch->q.len can be inflated by packets in sch->gso_skb, and an enqueue() on an empty SFQ qdisc can be followed by an immediate drop. Fix sfq_drop() to properly clear q->tail in this situation. Tested: ip netns add lb ip link add dev to-lb type veth peer name in-lb netns lb ethtool -K to-lb tso off # force qdisc to requeue gso_skb ip netns exec lb ethtool -K in-lb gro on # enable NAPI ip link set dev to-lb up ip -netns lb link set dev in-lb up ip addr add dev to-lb 192.168.20.1/24 ip -netns lb addr add dev in-lb 192.168.20.2/24 tc qdisc replace dev to-lb root sfq limit 100 ip netns exec lb netserver netperf -H 192.168.20.2 -l 100 & netperf -H 192.168.20.2 -l 100 & netperf -H 192.168.20.2 -l 100 & netperf -H 192.168.20.2 -l 100 & Fixes: a53851e2 ("net: sched: explicit locking in gso_cpu fallback") Reported-by:Marcus Wichelmann <marcus.wichelmann@hetzner-cloud.de> Closes: https://lore.kernel.org/netdev/9da42688-bfaa-4364-8797-e9271f3bdaef@hetzner-cloud.de/ Signed-off-by:
Eric Dumazet <edumazet@google.com> Reviewed-by:
Toke Høiland-Jørgensen <toke@redhat.com> Link: https://patch.msgid.link/20250606165127.3629486-1-edumazet@google.com Signed-off-by:
Jakub Kicinski <kuba@kernel.org> Signed-off-by:
Sasha Levin <sashal@kernel.org>
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