Re: [syzbot] [net?] KASAN: slab-use-after-free Read in taprio_dump

[Hillf Danton]

On Mon, 18 Dec 2023 06:33:26 -0800
> HEAD commit:    d5b235ec8eab Merge branch 'for-next/core' into for-kernelci
> git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15e40371e80000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git  d5b235ec8eab

--- x/net/sched/sch_taprio.c
+++ y/net/sched/sch_taprio.c
@@ -2393,6 +2393,7 @@ static int taprio_dump(struct Qdisc *sch
 	struct sched_gate_list *oper, *admin;
 	struct tc_mqprio_qopt opt = { 0 };
 	struct nlattr *nest, *sched_nest;
+	int active = hrtimer_cancel(&q->advance_timer);
 
 	oper = rtnl_dereference(q->oper_sched);
 	admin = rtnl_dereference(q->admin_sched);
@@ -2436,6 +2437,10 @@ static int taprio_dump(struct Qdisc *sch
 	nla_nest_end(skb, sched_nest);
 
 done:
+	if (active)
+		hrtimer_start(&q->advance_timer,
+				hrtimer_get_expires(&q->advance_timer),
+				HRTIMER_MODE_ABS);
 	return nla_nest_end(skb, nest);
 
 admin_error:
@@ -2445,6 +2450,10 @@ options_error:
 	nla_nest_cancel(skb, nest);
 
 start_error:
+	if (active)
+		hrtimer_start(&q->advance_timer,
+				hrtimer_get_expires(&q->advance_timer),
+				HRTIMER_MODE_ABS);
 	return -ENOSPC;
 }
 
--