5.4-stable review patch. If anyone has any objections, please let me know.
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From: Cong Wang xiyou.wangcong@gmail.com
[ Upstream commit ce8fe975fd99b49c29c42e50f2441ba53112b2e8 ]
In the current implementation, skbprio enqueue/dequeue contains an assertion that fails under certain conditions when SKBPRIO is used as a child qdisc under TBF with specific parameters. The failure occurs because TBF sometimes peeks at packets in the child qdisc without actually dequeuing them when tokens are unavailable.
This peek operation creates a discrepancy between the parent and child qdisc queue length counters. When TBF later receives a high-priority packet, SKBPRIO's queue length may show a different value than what's reflected in its internal priority queue tracking, triggering the assertion.
The fix removes this overly strict assertions in SKBPRIO, they are not necessary at all.
Reported-by: syzbot+a3422a19b05ea96bee18@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=a3422a19b05ea96bee18 Fixes: aea5f654e6b7 ("net/sched: add skbprio scheduler") Cc: Nishanth Devarajan ndev2021@gmail.com Signed-off-by: Cong Wang xiyou.wangcong@gmail.com Acked-by: Paolo Abeni pabeni@redhat.com Link: https://patch.msgid.link/20250329222536.696204-2-xiyou.wangcong@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/sched/sch_skbprio.c | 3 --- 1 file changed, 3 deletions(-)
diff --git a/net/sched/sch_skbprio.c b/net/sched/sch_skbprio.c index 7a5e4c4547156..7dca66026ca4d 100644 --- a/net/sched/sch_skbprio.c +++ b/net/sched/sch_skbprio.c @@ -121,8 +121,6 @@ static int skbprio_enqueue(struct sk_buff *skb, struct Qdisc *sch, /* Check to update highest and lowest priorities. */ if (skb_queue_empty(lp_qdisc)) { if (q->lowest_prio == q->highest_prio) { - /* The incoming packet is the only packet in queue. */ - BUG_ON(sch->q.qlen != 1); q->lowest_prio = prio; q->highest_prio = prio; } else { @@ -154,7 +152,6 @@ static struct sk_buff *skbprio_dequeue(struct Qdisc *sch) /* Update highest priority field. */ if (skb_queue_empty(hpq)) { if (q->lowest_prio == q->highest_prio) { - BUG_ON(sch->q.qlen); q->highest_prio = 0; q->lowest_prio = SKBPRIO_MAX_PRIORITY - 1; } else {