On Wed, Mar 4, 2020 at 11:29 AM Hillf Danton <hdanton@xxxxxxxx> wrote: > On Wed, 04 Mar 2020 00:08:11 -0800 > > syzbot found the following crash on: > > > > HEAD commit: 63623fd4 Merge tag 'for-linus' of git://git.kernel.org/pub.. > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=15257ba1e00000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=9833e26bab355358 > > dashboard link: https://syzkaller.appspot.com/bug?extid=0c5c2dbf76930df91489 > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > > > Unfortunately, I don't have any reproducer for this crash yet. > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > Reported-by: syzbot+0c5c2dbf76930df91489@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > rcu: INFO: rcu_preempt self-detected stall on CPU > > rcu: 0-....: (1 GPs behind) idle=576/1/0x4000000000000002 softirq=55718/56054 fqs=5235 > > (t=10500 jiffies g=63445 q=1523) > > NMI backtrace for cpu 0 > > CPU: 0 PID: 18804 Comm: syz-executor.4 Not tainted 5.6.0-rc3-syzkaller #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > Call Trace: > > <IRQ> > > __dump_stack lib/dump_stack.c:77 [inline] > > dump_stack+0x197/0x210 lib/dump_stack.c:118 > > nmi_cpu_backtrace.cold+0x70/0xb2 lib/nmi_backtrace.c:101 > > nmi_trigger_cpumask_backtrace+0x23b/0x28b lib/nmi_backtrace.c:62 > > arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 > > trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline] > > rcu_dump_cpu_stacks+0x183/0x1cf kernel/rcu/tree_stall.h:254 > > print_cpu_stall kernel/rcu/tree_stall.h:475 [inline] > > check_cpu_stall kernel/rcu/tree_stall.h:549 [inline] > > rcu_pending kernel/rcu/tree.c:3030 [inline] > > rcu_sched_clock_irq.cold+0x51a/0xc37 kernel/rcu/tree.c:2276 > > update_process_times+0x2d/0x70 kernel/time/timer.c:1726 > > tick_sched_handle+0xa2/0x190 kernel/time/tick-sched.c:171 > > tick_sched_timer+0x53/0x140 kernel/time/tick-sched.c:1314 > > __run_hrtimer kernel/time/hrtimer.c:1517 [inline] > > __hrtimer_run_queues+0x364/0xe40 kernel/time/hrtimer.c:1579 > > hrtimer_interrupt+0x314/0x770 kernel/time/hrtimer.c:1641 > > local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1119 [inline] > > smp_apic_timer_interrupt+0x160/0x610 arch/x86/kernel/apic/apic.c:1144 > > apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829 > > </IRQ> > > RIP: 0010:__sanitizer_cov_trace_const_cmp4+0x16/0x20 kernel/kcov.c:276 > > Code: 48 89 e5 48 8b 4d 08 e8 d8 fe ff ff 5d c3 66 0f 1f 44 00 00 55 89 f2 89 fe bf 05 00 00 00 48 89 e5 48 8b 4d 08 e8 ba fe ff ff <5d> c3 0f 1f 84 00 00 00 00 00 55 48 89 f2 48 89 fe bf 07 00 00 00 > > RSP: 0018:ffffc900053877d8 EFLAGS: 00000297 ORIG_RAX: ffffffffffffff13 > > RAX: 0000000000000002 RBX: 584279fc973b765a RCX: ffffffff83b71a81 > > RDX: 00000000ffffff75 RSI: 0000000000000000 RDI: 0000000000000005 > > RBP: ffffc900053877d8 R08: ffff888041a265c0 R09: 0000000000000092 > > R10: ffffed1015d0707b R11: ffff8880ae8383db R12: ffff88809eb56398 > > R13: 000000003ab2c4e4 R14: 1b0d4377a72d08f5 R15: 00000000ffffff75 > > mpihelp_submul_1+0x161/0x1a0 lib/mpi/generic_mpih-mul3.c:45 > > mpihelp_divrem+0x1ce/0x1360 lib/mpi/mpih-div.c:209 > > mpi_powm+0xffb/0x1d20 lib/mpi/mpi-pow.c:205 > > _compute_val crypto/dh.c:39 [inline] > > dh_compute_value+0x373/0x610 crypto/dh.c:178 > > crypto_kpp_generate_public_key include/crypto/kpp.h:315 [inline] > > __keyctl_dh_compute+0x9ae/0x1470 security/keys/dh.c:367 > > keyctl_dh_compute+0xcf/0x12d security/keys/dh.c:422 > > __do_sys_keyctl security/keys/keyctl.c:1818 [inline] > > __se_sys_keyctl security/keys/keyctl.c:1714 [inline] > > __x64_sys_keyctl+0x159/0x470 security/keys/keyctl.c:1714 > > do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 > > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > RIP: 0033:0x45c479 > > Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 > > RSP: 002b:00007f872a51fc78 EFLAGS: 00000246 ORIG_RAX: 00000000000000fa > > RAX: ffffffffffffffda RBX: 00007f872a5206d4 RCX: 000000000045c479 > > RDX: 0000000020002700 RSI: 0000000020000400 RDI: 0000000000000017 > > RBP: 000000000076bfc0 R08: 0000000000000000 R09: 0000000000000000 > > R10: 00000000ffffff84 R11: 0000000000000246 R12: 00000000ffffffff > > R13: 00000000000006fa R14: 00000000004c9883 R15: 000000000076bfcc > > > > > > --- > > This bug 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 syzkaller@xxxxxxxxxxxxxxxx. > > > > syzbot will keep track of this bug report. See: > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > Cut the chance of being a cpu hog. > > --- a/lib/mpi/mpih-div.c > +++ b/lib/mpi/mpih-div.c > @@ -215,6 +215,8 @@ q_test: > > qp[i] = q; > n0 = np[dsize - 1]; > + > + cond_resched(); Isn't it looping infinitely? cond_resched() won't help in such case.
