Re: [syzbot] [net?] WARNING in est_timer

[Hillf Danton <hdanton@sina.com>]

> Date: Fri, 29 Aug 2025 06:22:30 -0700	[thread overview]
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    07d9df80082b Merge tag 'perf-tools-fixes-for-v6.17-2025-08..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=13d67262580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=e1e1566c7726877e
> dashboard link: https://syzkaller.appspot.com/bug?extid=72db9ee39db57c3fecc5
> compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1141c262580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13f69262580000

#syz test

--- x/net/core/gen_estimator.c
+++ y/net/core/gen_estimator.c
@@ -90,10 +90,12 @@ static void est_timer(struct timer_list
 	rate = (b_packets - est->last_packets) << (10 - est->intvl_log);
 	rate = (rate >> est->ewma_log) - (est->avpps >> est->ewma_log);
 
+	preempt_disable();
 	write_seqcount_begin(&est->seq);
 	est->avbps += brate;
 	est->avpps += rate;
 	write_seqcount_end(&est->seq);
+	preempt_enable();
 
 	est->last_bytes = b_bytes;
 	est->last_packets = b_packets;
--