INFO: task hung in filename_create (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 62872f95 Merge 4.4.174 into android-4.4
git tree: android-4.4
console output: https://syzkaller.appspot.com/x/log.txt?x=16caf070a00000
kernel config: https://syzkaller.appspot.com/x/.config?x=47bc4dd423780c4a
dashboard link: https://syzkaller.appspot.com/bug?extid=1781abdc0272d9b62d69
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+1781ab...@syzkaller.appspotmail.com

INFO: task syz-fuzzer:2086 blocked for more than 140 seconds.
Not tainted 4.4.174+ #4
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-fuzzer D ffff8800b6e0fc48 26848 2086 2079 0x00000000
ffff8800b6e0fc48 ffff8800b7a597c0 8e1bfe2a48f56745 ffff8800b7a597c0
0000000000000001 ffff8800b7a5a000 ffff8801db61f180 ffff8801db61f1a8
ffff8801db61e898 ffff8801b7455f00 ffff8800b7a597c0 ffffed0016dc1001
Call Trace:
[<ffffffff82709b79>] schedule+0x99/0x1d0 kernel/sched/core.c:3355
[<ffffffff8270a333>] schedule_preempt_disabled+0x13/0x20
kernel/sched/core.c:3388
[<ffffffff8270c492>] __mutex_lock_common kernel/locking/mutex.c:582
[inline]
[<ffffffff8270c492>] mutex_lock_nested+0x3c2/0xb80
kernel/locking/mutex.c:621
[<ffffffff814cb6e9>] filename_create+0x159/0x460 fs/namei.c:3511
[<ffffffff814cd3bd>] user_path_create fs/namei.c:3569 [inline]
[<ffffffff814cd3bd>] SYSC_mkdirat fs/namei.c:3711 [inline]
[<ffffffff814cd3bd>] SyS_mkdirat+0xbd/0x250 fs/namei.c:3703
[<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a
2 locks held by syz-fuzzer/2086:
#0: (sb_writers#4){.+.+.+}, at: [<ffffffff814fcd3f>] sb_start_write
include/linux/fs.h:1517 [inline]
#0: (sb_writers#4){.+.+.+}, at: [<ffffffff814fcd3f>]
mnt_want_write+0x3f/0xb0 fs/namespace.c:391
#1: (&type->i_mutex_dir_key#3/1){+.+.+.}, at: [<ffffffff814cb6e9>]
filename_create+0x159/0x460 fs/namei.c:3511
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 20 Comm: khungtaskd Not tainted 4.4.174+ #4
task: ffff8801da6f2f80 task.stack: ffff8801d9ed8000
RIP: 0010:[<ffffffff8109b617>] [<ffffffff8109b617>] _flat_send_IPI_mask
arch/x86/kernel/apic/apic_flat_64.c:62 [inline]
RIP: 0010:[<ffffffff8109b617>] [<ffffffff8109b617>]
flat_send_IPI_mask+0xf7/0x1b0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8801d9edfc88 EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fc300
RBP: ffff8801d9edfcb8 R08: 0000000000000018 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000003000000 R14: ffffffff82e5f2e0 R15: 0000000000000002
FS: 0000000000000000(0000) GS:ffff8801db600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c426083000 CR3: 00000001d53ea000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
0000000000000001 ffffffff82e5f2e0 ffffffff831a6ac0 fffffbfff0634c34
000000000001b6c0 0000000000000008 ffff8801d9edfcd8 ffffffff81092bee
0000000000000008 ffffffff82924260 ffff8801d9edfd30 ffffffff81ab8252
Call Trace:
[<ffffffff81092bee>] nmi_raise_cpu_backtrace+0x5e/0x80
arch/x86/kernel/apic/hw_nmi.c:33
[<ffffffff81ab8252>] nmi_trigger_all_cpu_backtrace.cold+0xa1/0xae
lib/nmi_backtrace.c:85
[<ffffffff81092ca4>] arch_trigger_all_cpu_backtrace+0x14/0x20
arch/x86/kernel/apic/hw_nmi.c:38
[<ffffffff813b4762>] trigger_all_cpu_backtrace include/linux/nmi.h:44
[inline]
[<ffffffff813b4762>] check_hung_task kernel/hung_task.c:125 [inline]
[<ffffffff813b4762>] check_hung_uninterruptible_tasks
kernel/hung_task.c:182 [inline]
[<ffffffff813b4762>] watchdog.cold+0xd3/0xee kernel/hung_task.c:238
[<ffffffff811342c3>] kthread+0x273/0x310 kernel/kthread.c:211
[<ffffffff82718fc5>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:537
Code: 00 c3 5f ff 80 e6 10 75 e1 41 c1 e5 18 44 89 2c 25 10 c3 5f ff 44 89
fa 09 da 80 cf 04 41 83 ff 02 0f 44 d3 89 14 25 00 c3 5f ff <41> f7 c4 00
02 00 00 75 1e 4c 89 e7 57 9d 0f 1f 44 00 00 e8 f1
NMI backtrace for cpu 1
CPU: 1 PID: 1935 Comm: rsyslogd Not tainted 4.4.174+ #4
task: ffff8800b8cbaf80 task.stack: ffff8801d6418000
RIP: 0010:[<ffffffff81309616>] [<ffffffff81309616>]
__sanitizer_cov_trace_pc+0x26/0x50 kernel/kcov.c:100
RSP: 0018:ffff8801d641f860 EFLAGS: 00000046
RAX: ffff8800b8cbaf80 RBX: ffffffff8285550b RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff81acb49e RDI: ffffffff82855505
RBP: ffff8801d641f860 R08: 000000000000000a R09: 0000000000000005
R10: ffffffff83a4a4e0 R11: 0000000000000000 R12: ffff8801d641f9a0
R13: ffff8801d641f8f0 R14: dffffc0000000000 R15: 0000000000000030
FS: 00007f2f56519700(0000) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c428a8f000 CR3: 00000000b8c1e000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
ffff8801d641f918 ffffffff81acb49e 0000000041b58ab3 ffffffff82c75fd1
1ffff1003ac83f12 ffffffff82855505 0000000041b58ab3 ffffffff82c75eff
ffffffff81acb350 ffff8800b4ccad00 ffffffff8285550b ffff8801da401140
Call Trace:
[<ffffffff81acb49e>] format_decode+0x14e/0xb80 lib/vsprintf.c:1659
[<ffffffff81ad50d9>] vsnprintf+0x169/0x18a0 lib/vsprintf.c:1856
[<ffffffff81ad696b>] snprintf+0xbb/0xf0 lib/vsprintf.c:2037
[<ffffffff8121d6aa>] print_time kernel/printk/printk.c:1059 [inline]
[<ffffffff8121d6aa>] print_time kernel/printk/printk.c:1049 [inline]
[<ffffffff8121d6aa>] print_prefix+0x1ca/0x2e0 kernel/printk/printk.c:1084
[<ffffffff8121d8d6>] msg_print_text+0x116/0x2d0 kernel/printk/printk.c:1121
[<ffffffff8121f218>] syslog_print kernel/printk/printk.c:1176 [inline]
[<ffffffff8121f218>] do_syslog kernel/printk/printk.c:1336 [inline]
[<ffffffff8121f218>] do_syslog+0x7f8/0xaf0 kernel/printk/printk.c:1306
[<ffffffff81608274>] kmsg_read+0x74/0xa0 fs/proc/kmsg.c:39
[<ffffffff815e03bd>] proc_reg_read+0xfd/0x180 fs/proc/inode.c:202
[<ffffffff81496556>] __vfs_read+0x116/0x3c0 fs/read_write.c:434
[<ffffffff81498264>] vfs_read+0x134/0x360 fs/read_write.c:456
[<ffffffff8149aa8c>] SYSC_read fs/read_write.c:571 [inline]
[<ffffffff8149aa8c>] SyS_read+0xdc/0x1c0 fs/read_write.c:564
[<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a
Code: fe ff ff 66 90 55 48 89 e5 48 8b 75 08 65 48 8b 04 25 80 67 01 00 65
8b 15 08 d1 d0 7e 81 e2 00 01 1f 00 75 2b 8b 90 50 12 00 00 <83> fa 02 75
20 48 8b 88 58 12 00 00 8b 80 54 12 00 00 48 8b 11


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.