On Fri, Jul 31, 2020 at 8:44 AM syzbot <syzbot+8472ea265fe32cc3b...@syzkaller.appspotmail.com> wrote: > > Hello, > > syzbot found the following issue on: > > HEAD commit: 92ed3019 Linux 5.8-rc7 > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=10e84cdf100000 > kernel config: https://syzkaller.appspot.com/x/.config?x=b45e47f6d958ae82 > dashboard link: https://syzkaller.appspot.com/bug?extid=8472ea265fe32cc3bf78 > compiler: gcc (GCC) 10.1.0-syz 20200507 > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+8472ea265fe32cc3b...@syzkaller.appspotmail.com
This is a qemu-kvm instance killing the host kernel somehow, the host kernel itself running qemu's is full of rcu stalls. I think this is not a bug in the tested kernel. We change rcu stall timeout to 120 seconds from the default 21s, but this happens only after boot using sysctls. I did not find any way to change the rcu timeout via cmdline/config (would be useful). > hrtimer: interrupt took 42698779 ns > random: crng init done > watchdog: BUG: soft lockup - CPU#3 stuck for 21s! [grep:4749] > Modules linked in: > hardirqs last enabled at (2780): [<ffffffff88200204>] > __do_softirq+0x204/0xa60 kernel/softirq.c:276 > hardirqs last disabled at (2781): [<ffffffff87e5b2ed>] > idtentry_enter_cond_rcu+0x1d/0x50 arch/x86/entry/common.c:649 > softirqs last enabled at (2760): [<ffffffff88200748>] > __do_softirq+0x748/0xa60 kernel/softirq.c:319 > softirqs last disabled at (2779): [<ffffffff88000f0f>] > asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:711 > CPU: 3 PID: 4749 Comm: grep Not tainted 5.8.0-rc7-syzkaller #0 > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS > rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014 > RIP: 0010:__do_softirq+0x22f/0xa60 kernel/softirq.c:278 > Code: c7 c0 98 e0 b4 89 48 c1 e8 03 42 80 3c 30 00 0f 85 70 07 00 00 48 83 3d > 76 de 94 01 00 0f 84 4a 06 00 00 fb 66 0f 1f 44 00 00 <48> c7 44 24 08 c0 90 > a0 89 b8 ff ff ff ff 0f bc 04 24 83 c0 01 89 > RSP: 0000:ffffc90000598f70 EFLAGS: 00000286 > RAX: 1ffffffff1369c13 RBX: ffff8880294683c0 RCX: 0000000000000000 > RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff88200204 > R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff88000c3a > R13: 0000000000000000 R14: dffffc0000000000 R15: 0000000000000000 > FS: 00007fe02dd23700(0000) GS:ffff88802d100000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000000f5d1e8 CR3: 000000001efc6000 CR4: 0000000000340ee0 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > <IRQ> > </IRQ> > invoke_softirq kernel/softirq.c:387 [inline] > __irq_exit_rcu kernel/softirq.c:417 [inline] > irq_exit_rcu+0x229/0x270 kernel/softirq.c:429 > sysvec_apic_timer_interrupt+0x54/0x120 arch/x86/kernel/apic/apic.c:1091 > asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:585 > Code: ba 63 03 00 00 e8 f5 bf 00 00 0f 1f 44 00 00 48 89 5c 24 e0 48 89 6c 24 > e8 48 89 fb 4c 89 64 24 f0 4c 89 6c 24 f8 48 83 ec 38 <0f> b6 47 04 83 e0 0f > 83 f8 06 0f 85 3e 01 00 00 31 d2 66 83 7b 06 > RSP: 002b:00007ffd13103ee0 EFLAGS: 00010202 > RAX: 00000000000003b7 RBX: 00007fe02d584588 RCX: 0000000000000000 > RDX: 00007fe02d57d94c RSI: 0000000000000edc RDI: 00007fe02d584588 > RBP: 00007fe02dd2aef8 R08: 00000000004282a7 R09: 0000000000000004 > R10: 00007ffd13103f70 R11: 00007ffd13103f70 R12: 0000000000000004 > R13: 0000000010a0a9c4 R14: 0000000000000002 R15: 00007ffd131040f8 > > > --- > This report is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkal...@googlegroups.com. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > -- > You received this message because you are subscribed to the Google Groups > "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to syzkaller-bugs+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/syzkaller-bugs/00000000000060adcb05abb71eb6%40google.com.