Message-ID: <CACT4Y+buBxAhdTSJL1Zosx0sFcZ-r12vFALk-StnMEZCB8pf3g@mail.gmail.com>
Date:   Wed, 18 Jul 2018 13:44:34 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+3a0570f93c0d6ca388f5@...kaller.appspotmail.com>,
        Eric Van Hensbergen <ericvh@...il.com>,
        Ron Minnich <rminnich@...dia.gov>,
        Latchesar Ionkov <lucho@...kov.net>,
        v9fs-developer@...ts.sourceforge.net
Cc:     linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: INFO: task hung in utimes_common

On Tue, Jul 10, 2018 at 10:09 AM, Dmitry Vyukov <dvyukov@...gle.com> wrote:
> On Tue, Jul 10, 2018 at 10:08 AM, syzbot
> <syzbot+3a0570f93c0d6ca388f5@...kaller.appspotmail.com> wrote:
>> Hello,
>>
>> syzbot found the following crash on:
>>
>> HEAD commit:    d00d6d9a339d Add linux-next specific files for 20180709
>> git tree:       linux-next
>> console output: https://syzkaller.appspot.com/x/log.txt?x=17fdd90c400000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=94fe2b586beccacd
>> dashboard link: https://syzkaller.appspot.com/bug?extid=3a0570f93c0d6ca388f5
>> compiler:       gcc (GCC) 8.0.1 20180413 (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+3a0570f93c0d6ca388f5@...kaller.appspotmail.com
>
>
> Look similar to the other hangs in 9p, this time caused by the
> following program:
>
> 21:30:55 executing program 0:
> pipe2$9p(&(0x7f0000000100)={<r0=>0xffffffffffffffff,
> <r1=>0xffffffffffffffff}, 0x0)
> write$P9_RUNLINKAT(r1, &(0x7f0000000040)={0xffffffffffffffca, 0x4d}, 0x7)
> mkdir(&(0x7f0000000300)='./file0\x00', 0x0)
> mount$9p_fd(0x0, &(0x7f00000000c0)='./file0\x00',
> &(0x7f0000000340)='9p\x00', 0x0, &(0x7f00000001c0)={'trans=fd,',
> {'rfdno', 0x3d, r0}, 0x2c, {'wfdno', 0x3d, r1}, 0x2c})
> write$P9_RREADDIR(r1, &(0x7f0000000480)={0x2a, 0x29, 0x1, {0x0, [{{},
> 0x0, 0x0, 0x7, './file0'}]}}, 0x2a)
> write$P9_RGETATTR(r1, &(0x7f0000000200)={0xa0, 0x19, 0x1}, 0xa0)
> write$P9_RWALK(r1, &(0x7f0000000500)=ANY=[@ANYBLOB="090100006f01000000"], 0x9)
> mount$9p_fd(0x0, &(0x7f0000000080)='./file0\x00',
> &(0x7f0000000900)='9p\x00', 0x0, &(0x7f0000000840)={'trans=fd,',
> {'rfdno', 0x3d, r0}, 0x2c, {'wfdno', 0x3d, r1}, 0x2c,
> {[{@...ess_uid={'access', 0x3d}, 0x2c}]}})
> r2 = socket$inet6(0xa, 0x1000000000002, 0x0)
> ioctl(r2, 0x8912, &(0x7f0000000280)="025cc83d6d345f8f762070")
> utimes(&(0x7f0000000180)='./file0\x00', &(0x7f0000000380))

#syz dup: INFO: task hung in flush_work


>> 9pnet_virtio: no channels available for device (null)
>> Unknown ioctl 44801
>> 9pnet_virtio: no channels available for device (null)
>> 9pnet: Insufficient options for proto=fd
>> 9pnet: Insufficient options for proto=fd
>> INFO: task syz-executor0:12044 blocked for more than 140 seconds.
>>       Not tainted 4.18.0-rc3-next-20180709+ #2
>> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>> syz-executor0   D25408 12044   4539 0x00000004
>> Call Trace:
>>  context_switch kernel/sched/core.c:2853 [inline]
>>  __schedule+0x87c/0x1ed0 kernel/sched/core.c:3501
>>  schedule+0xfb/0x450 kernel/sched/core.c:3545
>>  __rwsem_down_write_failed_common+0x95d/0x1630
>> kernel/locking/rwsem-xadd.c:566
>>  rwsem_down_write_failed+0xe/0x10 kernel/locking/rwsem-xadd.c:595
>>  call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:117
>>  __down_write arch/x86/include/asm/rwsem.h:142 [inline]
>>  down_write+0xaa/0x130 kernel/locking/rwsem.c:72
>>  inode_lock include/linux/fs.h:748 [inline]
>>  utimes_common.isra.1+0x45c/0x8e0 fs/utimes.c:90
>>  do_utimes+0x1f7/0x380 fs/utimes.c:156
>>  do_futimesat+0x249/0x350 fs/utimes.c:212
>>  __do_sys_utimes fs/utimes.c:225 [inline]
>>  __se_sys_utimes fs/utimes.c:222 [inline]
>>  __x64_sys_utimes+0x59/0x80 fs/utimes.c:222
>>  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>> RIP: 0033:0x455e29
>> Code: cc 64 48 8b 0c 25 f8 ff ff ff 48 3b 61 10 0f 86 ab 04 00 00 48 83 ec
>> 58 48 89 6c 24 50 48 8d 6c 24 50 48 8b 44 24 60 c6 00 00 <48> 8b 4c 24 68 48
>> 89 ca 48 89 50 08 48 8b 59 20 48 01 da 31 db 31
>> RSP: 002b:00007fac7c8b4c68 EFLAGS: 00000246 ORIG_RAX: 00000000000000eb
>> RAX: ffffffffffffffda RBX: 00007fac7c8b56d4 RCX: 0000000000455e29
>> RDX: 0000000000000000 RSI: 0000000020000380 RDI: 0000000020000180
>> RBP: 000000000072bff0 R08: 0000000000000000 R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
>> R13: 00000000004c2af0 R14: 00000000004d4600 R15: 0000000000000002
>> INFO: lockdep is turned off.
>> NMI backtrace for cpu 1
>> CPU: 1 PID: 898 Comm: khungtaskd Not tainted 4.18.0-rc3-next-20180709+ #2
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>> Google 01/01/2011
>> Call Trace:
>>  __dump_stack lib/dump_stack.c:77 [inline]
>>  dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
>>  nmi_cpu_backtrace.cold.5+0x19/0xce lib/nmi_backtrace.c:103
>>  nmi_trigger_cpumask_backtrace+0x151/0x192 lib/nmi_backtrace.c:62
>>  arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
>>  trigger_all_cpu_backtrace include/linux/nmi.h:143 [inline]
>>  check_hung_uninterruptible_tasks kernel/hung_task.c:204 [inline]
>>  watchdog+0xb39/0x10b0 kernel/hung_task.c:265
>>  kthread+0x345/0x410 kernel/kthread.c:246
>>  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:415
>> Sending NMI from CPU 1 to CPUs 0:
>> NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0x6/0x10
>> arch/x86/include/asm/irqflags.h:54
>>
>>
>> ---
>> 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#bug-status-tracking for how to communicate with
>> syzbot.
>>
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