INFO: task hung in tty_ldisc_hangup

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: a844dc4c Linux 4.14.158
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1394b82ee00000
kernel config: https://syzkaller.appspot.com/x/.config?x=c02bef505ffc02ff
dashboard link: https://syzkaller.appspot.com/bug?extid=867ab30bf29852e02b1c
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10bba90ee00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16dee77ae00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+867ab3...@syzkaller.appspotmail.com

INFO: task login:6930 blocked for more than 140 seconds.
Not tainted 4.14.158-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
login D25920 6930 1 0x80000002
Call Trace:
context_switch kernel/sched/core.c:2808 [inline]
__schedule+0x7b8/0x1cd0 kernel/sched/core.c:3384
schedule+0x92/0x1c0 kernel/sched/core.c:3428
schedule_timeout+0x93b/0xe10 kernel/time/timer.c:1723
down_write_failed drivers/tty/tty_ldsem.c:298 [inline]
__ldsem_down_write_nested+0x304/0x7b0 drivers/tty/tty_ldsem.c:360
ldsem_down_write+0x33/0x39 drivers/tty/tty_ldsem.c:402
__tty_ldisc_lock drivers/tty/tty_ldisc.c:332 [inline]
tty_ldisc_lock+0x1e/0x50 drivers/tty/tty_ldisc.c:351
tty_ldisc_hangup+0x1a5/0x5e0 drivers/tty/tty_ldisc.c:751
__tty_hangup.part.0+0x2d3/0x6d0 drivers/tty/tty_io.c:622
__tty_hangup drivers/tty/tty_io.c:572 [inline]
tty_vhangup_session+0x25/0x30 drivers/tty/tty_io.c:732
disassociate_ctty.part.0+0x9b/0x6c0 drivers/tty/tty_jobctrl.c:266
disassociate_ctty+0x78/0x90 drivers/tty/tty_jobctrl.c:260
do_exit+0x1799/0x2c80 kernel/exit.c:852
do_group_exit+0x111/0x330 kernel/exit.c:951
SYSC_exit_group kernel/exit.c:962 [inline]
SyS_exit_group+0x1d/0x20 kernel/exit.c:960
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7f90c82b51e8
RSP: 002b:00007ffced52ade8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f90c82b51e8
RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
RBP: 00007f90c858a840 R08: 00000000000000e7 R09: ffffffffffffffa8
R10: 00007f90c8590740 R11: 0000000000000246 R12: 00007f90c858a840
R13: 0000000000000001 R14: 0000000000000001 R15: 000000000060b798

Showing all locks held in the system:
1 lock held by khungtaskd/1045:
#0: (tasklist_lock){.+.+}, at: [<ffffffff8148c8a8>]
debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4544
2 locks held by getty/6927:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff866549c3>]
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff83490d76>]
n_tty_read+0x1e6/0x17b0 drivers/tty/n_tty.c:2156
2 locks held by getty/6928:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff866549c3>]
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff83490d76>]
n_tty_read+0x1e6/0x17b0 drivers/tty/n_tty.c:2156
2 locks held by getty/6929:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff866549c3>]
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff83490d76>]
n_tty_read+0x1e6/0x17b0 drivers/tty/n_tty.c:2156
2 locks held by login/6930:
#0: (&tty->legacy_mutex){+.+.}, at: [<ffffffff834a33d8>]
tty_lock+0x68/0x80 drivers/tty/tty_mutex.c:19
#1: (&tty->ldisc_sem){++++}, at: [<ffffffff86654a03>]
ldsem_down_write+0x33/0x39 drivers/tty/tty_ldsem.c:402
2 locks held by getty/6931:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff866549c3>]
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff83490d76>]
n_tty_read+0x1e6/0x17b0 drivers/tty/n_tty.c:2156
2 locks held by getty/6932:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff866549c3>]
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff83490d76>]
n_tty_read+0x1e6/0x17b0 drivers/tty/n_tty.c:2156
2 locks held by getty/6933:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff866549c3>]
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff83490d76>]
n_tty_read+0x1e6/0x17b0 drivers/tty/n_tty.c:2156

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 1045 Comm: khungtaskd Not tainted 4.14.158-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x142/0x197 lib/dump_stack.c:58
nmi_cpu_backtrace.cold+0x57/0x94 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x141/0x189 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:140 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:195 [inline]
watchdog+0x5e7/0xb90 kernel/hung_task.c:274
kthread+0x319/0x430 kernel/kthread.c:232
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 7114 Comm: syz-executor778 Not tainted 4.14.158-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
task: ffff88808460c580 task.stack: ffff888085688000
RIP: 0010:rcu_sched_qs+0x5/0x1b0 kernel/rcu/tree.c:231
RSP: 0018:ffff88808568f850 EFLAGS: 00000082
RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffff88808460ce00
RDX: dffffc0000000000 RSI: ffffffff87f88820 RDI: 0000000000000082
RBP: ffff88808568f858 R08: ffff88808460c580 R09: ffff88808460ce48
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 000000000002b540 R14: ffff88808460c580 R15: ffff8880aec2b540
FS: 00000000021f2880(0000) GS:ffff8880aec00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000001feb000 CR3: 0000000097d81000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
rcu_note_context_switch+0x3d/0x1600 kernel/rcu/tree.c:457
__schedule+0x1d2/0x1cd0 kernel/sched/core.c:3314
schedule+0x92/0x1c0 kernel/sched/core.c:3428
paste_selection+0x293/0x3f2 drivers/tty/vt/selection.c:355
tioclinux+0x10e/0x400 drivers/tty/vt/vt.c:2696
vt_ioctl+0x180c/0x2170 drivers/tty/vt/vt_ioctl.c:364
tty_ioctl+0x841/0x1320 drivers/tty/tty_io.c:2661
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x7ae/0x1060 fs/ioctl.c:684
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x441239
RSP: 002b:00007fff0d09d828 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000441239
RDX: 0000000020000080 RSI: 000000000000541c RDI: 0000000000000003
RBP: 00000000000aee71 R08: 000000000000000d R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402060
R13: 00000000004020f0 R14: 0000000000000000 R15: 0000000000000000
Code: c1 ea 03 80 3c 02 00 75 07 48 8b 43 58 5b 5d c3 e8 d1 4f 39 00 eb f2
0f 1f 44 00 00 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 53 <48> 83 ec 08
e8 72 f4 fe ff 85 c0 74 09 80 3d 51 28 5f 07 00 74


---
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 syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: fb683b5e Linux 4.19.88
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=133e542ae00000
kernel config: https://syzkaller.appspot.com/x/.config?x=aa0c39a6a0078b1c
dashboard link: https://syzkaller.appspot.com/bug?extid=dab078f17445b023b621

compiler: gcc (GCC) 9.0.0 20181231 (experimental)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12128f36e00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=106aadb1e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:

Reported-by: syzbot+dab078...@syzkaller.appspotmail.com

INFO: task login:7493 blocked for more than 140 seconds.
Not tainted 4.19.88-syzkaller #0

"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

login D25064 7493 1 0x80000002
Call Trace:
context_switch kernel/sched/core.c:2826 [inline]
__schedule+0x866/0x1dc0 kernel/sched/core.c:3515
schedule+0x92/0x1c0 kernel/sched/core.c:3559
schedule_timeout+0x8c8/0xfc0 kernel/time/timer.c:1782
down_write_failed drivers/tty/tty_ldsem.c:284 [inline]
__ldsem_down_write_nested+0x3b3/0x8f0 drivers/tty/tty_ldsem.c:346
ldsem_down_write+0x33/0x40 drivers/tty/tty_ldsem.c:388
__tty_ldisc_lock drivers/tty/tty_ldisc.c:320 [inline]
tty_ldisc_lock+0x1e/0x60 drivers/tty/tty_ldisc.c:339
tty_ldisc_hangup+0x1b8/0x630 drivers/tty/tty_ldisc.c:739
__tty_hangup.part.0+0x306/0x720 drivers/tty/tty_io.c:623
__tty_hangup drivers/tty/tty_io.c:573 [inline]
tty_vhangup_session+0x25/0x30 drivers/tty/tty_io.c:733
disassociate_ctty.part.0+0xb4/0x6f0 drivers/tty/tty_jobctrl.c:267
disassociate_ctty+0x81/0xa0 drivers/tty/tty_jobctrl.c:261
do_exit+0x17bb/0x3080 kernel/exit.c:874
do_group_exit+0x135/0x370 kernel/exit.c:979
__do_sys_exit_group kernel/exit.c:990 [inline]
__se_sys_exit_group kernel/exit.c:988 [inline]
__x64_sys_exit_group+0x44/0x50 kernel/exit.c:988
do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f02a5aa71e8
Code: Bad RIP value.
RSP: 002b:00007ffefb505428 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f02a5aa71e8

RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000

RBP: 00007f02a5d7c840 R08: 00000000000000e7 R09: ffffffffffffffa8
R10: 00007f02a5d82740 R11: 0000000000000246 R12: 00007f02a5d7c840

R13: 0000000000000001 R14: 0000000000000001 R15: 000000000060b798

Showing all locks held in the system:

1 lock held by khungtaskd/1069:
#0: 00000000e82d5014 (rcu_read_lock){....}, at:
debug_show_all_locks+0x5f/0x27e kernel/locking/lockdep.c:4438
2 locks held by rs:main Q:Reg/7365:
1 lock held by rsyslogd/7367:
#0: 00000000ea74e499 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xee/0x110
fs/file.c:767
2 locks held by getty/7490:
#0: 00000000707e5237 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 000000001a31bcab (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7491:
#0: 0000000037ee0d65 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 00000000d50b0637 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7492:
#0: 00000000a8c550c9 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 00000000ae89fffb (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by login/7493:
#0: 00000000b23e8d29 (&tty->legacy_mutex){+.+.}, at: tty_lock+0x73/0xb0
drivers/tty/tty_mutex.c:19
#1: 0000000011e7398d (&tty->ldisc_sem){++++}, at:
ldsem_down_write+0x33/0x40 drivers/tty/tty_ldsem.c:388

2 locks held by getty/7494:

#0: 0000000012ba2c9c (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 00000000374027ce (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154

2 locks held by getty/7495:

#0: 00000000f7d60692 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 000000006bf0e224 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154

2 locks held by getty/7496:

#0: 00000000a247e517 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 000000006fdc391e (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by syz-executor534/7663:

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 1069 Comm: khungtaskd Not tainted 4.19.88-syzkaller #0

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+0x197/0x210 lib/dump_stack.c:118
nmi_cpu_backtrace.cold+0x63/0xa4 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x1b0/0x1f8 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:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:203 [inline]
watchdog+0x9df/0xee0 kernel/hung_task.c:287
kthread+0x354/0x420 kernel/kthread.c:246
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
Sending NMI from CPU 0 to CPUs 1:

NMI backtrace for cpu 1

CPU: 1 PID: 7663 Comm: syz-executor534 Not tainted 4.19.88-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011

RIP: 0010:match_held_lock+0x12/0x500 kernel/locking/lockdep.c:3471
Code: b3 fe ff ff 48 c7 c7 68 5c f2 88 e8 b8 2d 51 00 e9 1d ff ff ff 0f 1f
00 48 b8 00 00 00 00 00 fc ff df 55 48 89 e5 41 57 41 56 <41> 55 41 54 53
48 89 fb 48 83 c7 10 48 89 fa 48 83 ec 08 48 c1 ea
RSP: 0018:ffff8880915af748 EFLAGS: 00000002
RAX: dffffc0000000000 RBX: ffff88809519c200 RCX: ffff88809519ca80
RDX: 0000000000000000 RSI: ffff8880ae92c258 RDI: ffff88809519cad0
RBP: ffff8880915af758 R08: ffff88809519c200 R09: ffffed1015d25849
R10: ffffed1015d25848 R11: ffff8880ae92c243 R12: ffff8880ae92c258
R13: ffffed1012a3394f R14: 0000000000000002 R15: ffff88809519cad0
FS: 00000000022be880(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: ffffffffff600400 CR3: 0000000081635000 CR4: 00000000001406e0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:

__lock_is_held+0xb6/0x140 kernel/locking/lockdep.c:3723
lock_is_held_type+0x110/0x210 kernel/locking/lockdep.c:3941
lock_is_held include/linux/lockdep.h:344 [inline]
update_rq_clock+0x21c/0x2b0 kernel/sched/core.c:190
__schedule+0x253/0x1dc0 kernel/sched/core.c:3458
schedule+0x92/0x1c0 kernel/sched/core.c:3559
paste_selection+0x2e8/0x443 drivers/tty/vt/selection.c:354
tioclinux+0x133/0x470 drivers/tty/vt/vt.c:3019
vt_ioctl+0x19ab/0x2530 drivers/tty/vt/vt_ioctl.c:364
tty_ioctl+0x7f3/0x1510 drivers/tty/tty_io.c:2669
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0xd5f/0x1380 fs/ioctl.c:688
ksys_ioctl+0xab/0xd0 fs/ioctl.c:705
__do_sys_ioctl fs/ioctl.c:712 [inline]
__se_sys_ioctl fs/ioctl.c:710 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:710
do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4416e9
Code: e8 bc b2 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 6b 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fff2472ae38 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000007bb3a RCX: 00000000004416e9

RDX: 0000000020000080 RSI: 000000000000541c RDI: 0000000000000003

RBP: 0000000000000000 R08: 000000000000000d R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000008f
R13: 0000000000402470 R14: 0000000000000000 R15: 0000000000000000

[syzbot]

syzbot suspects this bug was fixed by commit:

commit b4492f1e7456bd162714c0ec2815c2749d930844
Author: Jiri Slaby <jsl...@suse.cz>
Date: Fri Feb 28 11:54:06 2020 +0000

vt: selection, push sel_lock up

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=149fa1f9e00000
start commit: 672481c2 Linux 4.19.91
git tree: linux-4.19.y
kernel config: https://syzkaller.appspot.com/x/.config?x=445a712574d168a6
dashboard link: https://syzkaller.appspot.com/bug?extid=dab078f17445b023b621
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13220ac1e00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10905ac1e00000

If the result looks correct, please mark the bug fixed by replying with:

#syz fix: vt: selection, push sel_lock up

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[syzbot]

syzbot suspects this bug was fixed by commit:

commit a4719f6d07b2c63223f7452c435c5f578f105cfe

Author: Jiri Slaby <jsl...@suse.cz>
Date: Fri Feb 28 11:54:06 2020 +0000

vt: selection, push sel_lock up

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=15c90b55e00000
start commit: e1f7d50a Linux 4.14.160
git tree: linux-4.14.y
kernel config: https://syzkaller.appspot.com/x/.config?x=46599517442ad9fb
dashboard link: https://syzkaller.appspot.com/bug?extid=867ab30bf29852e02b1c
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=103224aee00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17ea5351e00000