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Message-ID: <CACT4Y+Zqm=kYx5weFtDROs1u8vNqW8oy-Dt05tsq1xZ=KLUFUw@mail.gmail.com>
Date: Thu, 4 Jan 2018 15:01:06 +0100
From: Dmitry Vyukov <dvyukov@...gle.com>
To: Takashi Iwai <tiwai@...e.de>
Cc: alsa-devel@...a-project.org, Jaroslav Kysela <perex@...ex.cz>,
syzbot <syzbot+387f48da65cb522abfe8@...kaller.appspotmail.com>,
Frédéric Weisbecker <fweisbec@...il.com>,
syzkaller-bugs@...glegroups.com, Ingo Molnar <mingo@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: INFO: rcu detected stall in memcpy
On Thu, Jan 4, 2018 at 1:57 PM, Takashi Iwai <tiwai@...e.de> wrote:
> On Thu, 04 Jan 2018 13:08:45 +0100,
> Dmitry Vyukov wrote:
>>
>> On Thu, Jan 4, 2018 at 1:03 PM, syzbot
>> <syzbot+387f48da65cb522abfe8@...kaller.appspotmail.com> wrote:
>> > Hello,
>> >
>> > syzkaller hit the following crash on
>> > 30a7acd573899fd8b8ac39236eff6468b195ac7d
>> > git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
>> > compiler: gcc (GCC) 7.1.1 20170620
>> > .config is attached
>> > Raw console output is attached.
>> > Unfortunately, I don't have any reproducer for this bug yet.
>> >
>> >
>> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> > Reported-by: syzbot+387f48da65cb522abfe8@...kaller.appspotmail.com
>> > It will help syzbot understand when the bug is fixed. See footer for
>> > details.
>> > If you forward the report, please keep this part and the footer.
>>
>> This looks ALSA-related. +ALSA maintainers.
>
> Not sure exactly what triggers it. It's the simple memcpy(), and I
> don't know where RCU is involved in that code path.
>
> BTW, other two suspicious RCU usage reports are actually stopped at
> the second WARN_ON() after the RCU message, and the second WARN_ON()
> is independent from RCU; it's the known spurious WARN_ON() and was
> already removed in the sound git tree.
Hi Takashi,
Another similar one just popped up:
https://groups.google.com/forum/#!topic/syzkaller-bugs/X3d6-PIrJM0
This looks like mulaw_decode enters an infinite loop, or at least
doing very large amount of computations without a resched, e.g.
(uint64_t)-1 number of iterations of something along these lines.
>> > INFO: rcu_sched detected stalls on CPUs/tasks:
>> > (detected by 0, t=125002 jiffies, g=15654, c=15653, q=133)
>> > All QSes seen, last rcu_sched kthread activity 125002
>> > (4294863411-4294738409), jiffies_till_next_fqs=3, root ->qsmask 0x0
>> > syz-executor1 R running task 24936 11943 3739 0x0000000c
>> > Call Trace:
>> > <IRQ>
>> > sched_show_task+0x4a3/0x5e0 kernel/sched/core.c:5198
>> > print_other_cpu_stall+0x996/0x1090 kernel/rcu/tree.c:1564
>> > check_cpu_stall.isra.61+0x6e6/0x15b0 kernel/rcu/tree.c:1682
>> > __rcu_pending kernel/rcu/tree.c:3440 [inline]
>> > rcu_pending kernel/rcu/tree.c:3502 [inline]
>> > rcu_check_callbacks+0x256/0xd00 kernel/rcu/tree.c:2842
>> > update_process_times+0x30/0x60 kernel/time/timer.c:1628
>> > tick_sched_handle+0x85/0x160 kernel/time/tick-sched.c:162
>> > tick_sched_timer+0x42/0x120 kernel/time/tick-sched.c:1194
>> > __run_hrtimer kernel/time/hrtimer.c:1211 [inline]
>> > __hrtimer_run_queues+0x358/0xe20 kernel/time/hrtimer.c:1275
>> > hrtimer_interrupt+0x1c2/0x5e0 kernel/time/hrtimer.c:1309
>> > local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline]
>> > smp_apic_timer_interrupt+0x14a/0x700 arch/x86/kernel/apic/apic.c:1050
>> > apic_timer_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:920
>> > </IRQ>
>> > RIP: 0010:kasan_mem_to_shadow include/linux/kasan.h:30 [inline]
>> > RIP: 0010:memory_is_poisoned_n mm/kasan/kasan.c:210 [inline]
>> > RIP: 0010:memory_is_poisoned mm/kasan/kasan.c:241 [inline]
>> > RIP: 0010:check_memory_region_inline mm/kasan/kasan.c:257 [inline]
>> > RIP: 0010:check_memory_region+0x38/0x190 mm/kasan/kasan.c:267
>> > RSP: 0000:ffff8801bd2ff868 EFLAGS: 00000212 ORIG_RAX: ffffffffffffff11
>> > RAX: ffff7fffffffffff RBX: ffffc9000160020b RCX: ffffffff841fceaf
>> > RDX: 0000000000000001 RSI: 0000000000000002 RDI: ffffc9000160020a
>> > RBP: ffff8801bd2ff878 R08: ffffc9000160020a R09: dffffc0000000000
>> > R10: 0000000000000001 R11: ffffed0037a5ff2e R12: ffffc9000160020a
>> > R13: ffff8801bd2ff970 R14: dffffc0000000000 R15: ffffc9000160020a
>> > memcpy+0x37/0x50 mm/kasan/kasan.c:303
>> > memcpy include/linux/string.h:344 [inline]
>> > cvt_s16_to_native sound/core/oss/mulaw.c:164 [inline]
>> > mulaw_decode+0x52f/0x770 sound/core/oss/mulaw.c:195
>> > mulaw_transfer+0x222/0x270 sound/core/oss/mulaw.c:273
>> > snd_pcm_plug_write_transfer+0x22d/0x420 sound/core/oss/pcm_plugin.c:611
>> > snd_pcm_oss_write2+0x260/0x420 sound/core/oss/pcm_oss.c:1311
>> > snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1372 [inline]
>> > snd_pcm_oss_write+0x5fe/0x830 sound/core/oss/pcm_oss.c:2646
>> > __vfs_write+0xef/0x970 fs/read_write.c:480
>> > vfs_write+0x189/0x510 fs/read_write.c:544
>> > SYSC_write fs/read_write.c:589 [inline]
>> > SyS_write+0xef/0x220 fs/read_write.c:581
>> > entry_SYSCALL_64_fastpath+0x23/0x9a
>> > RIP: 0033:0x452ac9
>> > RSP: 002b:00007fa354a13c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000001
>> > RAX: ffffffffffffffda RBX: cccccccccccccccd RCX: 0000000000452ac9
>> > RDX: 00000000fffffeb2 RSI: 0000000020083fc6 RDI: 0000000000000014
>> > RBP: 00000000000005b5 R08: 0000000000000000 R09: 0000000000000000
>> > R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f6998
>> > R13: 00000000ffffffff R14: 00007fa354a146d4 R15: 0000000000000000
>> > rcu_sched kthread starved for 125002 jiffies! g15654 c15653 f0x2
>> > RCU_GP_WAIT_FQS(3) ->state=0x0 ->cpu=0
>> > rcu_sched R running task 23456 8 2 0x80000000
>> > Call Trace:
>> > context_switch kernel/sched/core.c:2799 [inline]
>> > __schedule+0x8eb/0x2060 kernel/sched/core.c:3375
>> > schedule+0xf5/0x430 kernel/sched/core.c:3434
>> > schedule_timeout+0x118/0x230 kernel/time/timer.c:1793
>> > rcu_gp_kthread+0x9e5/0x1930 kernel/rcu/tree.c:2314
>> > kthread+0x33c/0x400 kernel/kthread.c:238
>> > ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524
>> >
>> >
>> > ---
>> > This bug is generated by a dumb bot. It may contain errors.
>> > See https://goo.gl/tpsmEJ for details.
>> > Direct all questions to syzkaller@...glegroups.com.
>> >
>> > syzbot will keep track of this bug report.
>> > If you forgot to add the Reported-by tag, once the fix for this bug is
>> > merged
>> > into any tree, please reply to this email with:
>> > #syz fix: exact-commit-title
>> > To mark this as a duplicate of another syzbot report, please reply with:
>> > #syz dup: exact-subject-of-another-report
>> > If it's a one-off invalid bug report, please reply with:
>> > #syz invalid
>> > Note: if the crash happens again, it will cause creation of a new bug
>> > report.
>> > Note: all commands must start from beginning of the line in the email body.
>> >
>> > --
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