Message-ID: <CACT4Y+ZM_Si=bPUVU2rVgotOB+FQEbNEyuiMRxCCS+f7LjNe3g@mail.gmail.com>
Date:   Mon, 9 Jul 2018 15:29:04 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+6cd4d2845f652967921c@...kaller.appspotmail.com>,
        Eric Van Hensbergen <ericvh@...il.com>,
        Ron Minnich <rminnich@...dia.gov>,
        Latchesar Ionkov <lucho@...kov.net>,
        David Miller <davem@...emloft.net>,
        v9fs-developer@...ts.sourceforge.net,
        netdev <netdev@...r.kernel.org>
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 vfs_setxattr

On Mon, Jul 9, 2018 at 3:25 PM, syzbot
<syzbot+6cd4d2845f652967921c@...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=1414611c400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=94fe2b586beccacd
> dashboard link: https://syzkaller.appspot.com/bug?extid=6cd4d2845f652967921c
> 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+6cd4d2845f652967921c@...kaller.appspotmail.com

>From the log it looks like the following program caused the hang.
+9p maintainers

03:43:44 executing program 3:
pipe2$9p(&(0x7f0000000100)={<r0=>0xffffffffffffffff,
<r1=>0xffffffffffffffff}, 0x0)
write$P9_RUNLINKAT(r1, &(0x7f0000000040)={0xffffffffffffffca, 0x4d}, 0x7)
mkdir(&(0x7f0000000300)='./file0\x00', 0x100)
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_RSTATFS(r1, &(0x7f0000000640)={0x43, 0x9, 0x1}, 0x43)
write$P9_RREADDIR(r1, &(0x7f00000004c0)={0x3ea, 0x29, 0x1, {0x0,
[{{0x46, 0x2, 0x8}, 0x1000, 0x7, 0x7, './file0'}, {{0x40, 0x0, 0x2},
0x9, 0x7ff, 0x7, './file0'}, {{0x10, 0x3, 0x5}, 0x9, 0x2, 0x7,
'./file0'}, {{0x40, 0x1, 0x4}, 0x400, 0x2, 0x7, './file0'}]}}, 0x87)
write$P9_RREMOVE(r1, &(0x7f0000000180)={0x7, 0x7b, 0x1}, 0x7)
mount$9p_fd(0x0, &(0x7f0000000000)='./file0\x00',
&(0x7f0000000900)='9p\x00', 0x0, &(0x7f0000000840)={'trans=fd,',
{'rfdno', 0x3d, r0}, 0x2c, {'wfdno', 0x3d, r1}, 0x2c,
{[{@...ess_uid={'access', 0x3d}, 0x2c}]}})
setxattr(&(0x7f0000000140)='./file0\x00',
&(0x7f0000000380)=@...wn='system.posix_acl_default\x00',
&(0x7f0000000400)=':\x00', 0x2, 0x0)




> FAT-fs (loop6): Unrecognized mount option "uid=" or missing value
> INFO: task syz-executor3:28571 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-executor3   D25408 28571   4477 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]
>  vfs_setxattr+0x96/0x100 fs/xattr.c:218
>  setxattr+0x2ea/0x450 fs/xattr.c:450
>  path_setxattr+0x1e3/0x230 fs/xattr.c:469
>  __do_sys_setxattr fs/xattr.c:484 [inline]
>  __se_sys_setxattr fs/xattr.c:480 [inline]
>  __x64_sys_setxattr+0xc4/0x150 fs/xattr.c:480
>  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x455e29
> Code: Bad RIP value.
> RSP: 002b:00007f1c60d88c68 EFLAGS: 00000246 ORIG_RAX: 00000000000000bc
> RAX: ffffffffffffffda RBX: 00007f1c60d896d4 RCX: 0000000000455e29
> RDX: 0000000020000400 RSI: 0000000020000380 RDI: 0000000020000140
> RBP: 000000000072bff0 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000002 R11: 0000000000000246 R12: 00000000ffffffff
> R13: 00000000004bbff8 R14: 00000000004d3370 R15: 0000000000000002
> INFO: lockdep is turned off.
> NMI backtrace for cpu 1
> CPU: 1 PID: 897 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
> CPU: 0 PID: 2419 Comm: udevd Not tainted 4.18.0-rc3-next-20180709+ #2
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0033:0x4043d1
> Code: d5 b0 00 00 bf a0 54 62 00 e8 9b fb 00 00 bf b0 54 62 00 e8 91 fb 00
> 00 44 89 7c 24 64 4c 89 6c 24 50 49 89 df 44 89 74 24 58 <80> 3d b0 11 22 00
> 00 0f 84 88 07 00 00 83 7c 24 58 00 78 1e 8b 54
> RSP: 002b:00007ffee90bf370 EFLAGS: 00000246
> RAX: 0000000000000001 RBX: 0000000000000000 RCX: 00007ffee90bf46c
> RDX: 0000000000000004 RSI: 0000000000000001 RDI: 00000000006254a0
> RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000001
> R10: 0000000000000008 R11: 0000000000000004 R12: 0000000000000003
> R13: 0000000000000000 R14: 0000000000891520 R15: 0000000000883250
> FS:  00007f96fedce7a0(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffffffffff600400 CR3: 00000001ca6fa000 CR4: 00000000001406f0
> DR0: 0000000020000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
>
>
> ---
> 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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