Message-ID: <CACT4Y+ZyhwEsuGK9aJZ=4vXJ_AfHqFn6n5d58H_5E_-o9qHRWA@mail.gmail.com>
Date:   Wed, 4 Mar 2020 09:15:17 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+0c5c2dbf76930df91489@...kaller.appspotmail.com>
Cc:     David Miller <davem@...emloft.net>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Eric Biggers <ebiggers@...nel.org>, allison@...utok.net
Subject: Re: INFO: rcu detected stall in sys_keyctl

On Wed, Mar 4, 2020 at 9:08 AM syzbot
<syzbot+0c5c2dbf76930df91489@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> 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@...kaller.appspotmail.com
>
> 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

+lib/mpi maintainers

I wonder if this can also be triggered by remote actors (tls, wifi, usb, etc).

>  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@...glegroups.com.
>
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
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