[syzbot] INFO: task hung in sys_io_destroy

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 1d67c8d993ba Merge tag 'soc-fixes-5.14-1' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11b40232300000
kernel config: https://syzkaller.appspot.com/x/.config?x=f1b998c1afc13578
dashboard link: https://syzkaller.appspot.com/bug?extid=d40a01556c761b2cb385
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12453812300000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11225922300000

Bisection is inconclusive: the issue happens on the oldest tested release.

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=127cac6a300000
final oops: https://syzkaller.appspot.com/x/report.txt?x=117cac6a300000
console output: https://syzkaller.appspot.com/x/log.txt?x=167cac6a300000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d40a01...@syzkaller.appspotmail.com

INFO: task syz-executor299:8807 blocked for more than 143 seconds.
Not tainted 5.14.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor299 state:D stack:29400 pid: 8807 ppid: 8806 flags:0x00000000
Call Trace:
context_switch kernel/sched/core.c:4683 [inline]
__schedule+0x93a/0x26f0 kernel/sched/core.c:5940
schedule+0xd3/0x270 kernel/sched/core.c:6019
schedule_timeout+0x1db/0x2a0 kernel/time/timer.c:1854
do_wait_for_common kernel/sched/completion.c:85 [inline]
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common kernel/sched/completion.c:117 [inline]
wait_for_completion+0x176/0x280 kernel/sched/completion.c:138
__do_sys_io_destroy fs/aio.c:1402 [inline]
__se_sys_io_destroy fs/aio.c:1380 [inline]
__x64_sys_io_destroy+0x17e/0x1e0 fs/aio.c:1380
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x445899
RSP: 002b:00007f9b5a7e2318 EFLAGS: 00000246 ORIG_RAX: 00000000000000cf
RAX: ffffffffffffffda RBX: 00000000004ca428 RCX: 0000000000445899
RDX: 0000000000445899 RSI: 00000000000f4240 RDI: 00007f9b5a7c1000
RBP: 00000000004ca420 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000049a074
R13: 00007ffdd09518ef R14: 00007f9b5a7e2400 R15: 0000000000022000
INFO: task syz-executor299:8843 blocked for more than 143 seconds.
Not tainted 5.14.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor299 state:D stack:29184 pid: 8843 ppid: 8842 flags:0x00000000
Call Trace:
context_switch kernel/sched/core.c:4683 [inline]
__schedule+0x93a/0x26f0 kernel/sched/core.c:5940
schedule+0xd3/0x270 kernel/sched/core.c:6019
schedule_timeout+0x1db/0x2a0 kernel/time/timer.c:1854
do_wait_for_common kernel/sched/completion.c:85 [inline]
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common kernel/sched/completion.c:117 [inline]
wait_for_completion+0x176/0x280 kernel/sched/completion.c:138
__do_sys_io_destroy fs/aio.c:1402 [inline]
__se_sys_io_destroy fs/aio.c:1380 [inline]
__x64_sys_io_destroy+0x17e/0x1e0 fs/aio.c:1380
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x445899
RSP: 002b:00007f9b5a7e2318 EFLAGS: 00000246 ORIG_RAX: 00000000000000cf
RAX: ffffffffffffffda RBX: 00000000004ca428 RCX: 0000000000445899
RDX: 0000000000445899 RSI: 0000000000000000 RDI: 00007f9b5a7c1000
RBP: 00000000004ca420 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000049a074
R13: 00007ffdd09518ef R14: 00007f9b5a7e2400 R15: 0000000000022000
INFO: task syz-executor299:9076 blocked for more than 143 seconds.
Not tainted 5.14.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor299 state:D stack:29216 pid: 9076 ppid: 9075 flags:0x00000000
Call Trace:
context_switch kernel/sched/core.c:4683 [inline]
__schedule+0x93a/0x26f0 kernel/sched/core.c:5940
schedule+0xd3/0x270 kernel/sched/core.c:6019
schedule_timeout+0x1db/0x2a0 kernel/time/timer.c:1854
do_wait_for_common kernel/sched/completion.c:85 [inline]
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common kernel/sched/completion.c:117 [inline]
wait_for_completion+0x176/0x280 kernel/sched/completion.c:138
__do_sys_io_destroy fs/aio.c:1402 [inline]
__se_sys_io_destroy fs/aio.c:1380 [inline]
__x64_sys_io_destroy+0x17e/0x1e0 fs/aio.c:1380
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x445899
RSP: 002b:00007f9b5a7e2318 EFLAGS: 00000246 ORIG_RAX: 00000000000000cf
RAX: ffffffffffffffda RBX: 00000000004ca428 RCX: 0000000000445899
RDX: 0000000000445899 RSI: 0000000000000000 RDI: 00007f9b5a7c1000
RBP: 00000000004ca420 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000049a074
R13: 00007ffdd09518ef R14: 00007f9b5a7e2400 R15: 0000000000022000
INFO: task syz-executor299:9188 blocked for more than 143 seconds.
Not tainted 5.14.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor299 state:D stack:29400 pid: 9188 ppid: 9187 flags:0x00000000
Call Trace:
context_switch kernel/sched/core.c:4683 [inline]
__schedule+0x93a/0x26f0 kernel/sched/core.c:5940
schedule+0xd3/0x270 kernel/sched/core.c:6019
schedule_timeout+0x1db/0x2a0 kernel/time/timer.c:1854
do_wait_for_common kernel/sched/completion.c:85 [inline]
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common kernel/sched/completion.c:117 [inline]
wait_for_completion+0x176/0x280 kernel/sched/completion.c:138
__do_sys_io_destroy fs/aio.c:1402 [inline]
__se_sys_io_destroy fs/aio.c:1380 [inline]
__x64_sys_io_destroy+0x17e/0x1e0 fs/aio.c:1380
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x445899
RSP: 002b:00007f9b5a7e2318 EFLAGS: 00000246 ORIG_RAX: 00000000000000cf
RAX: ffffffffffffffda RBX: 00000000004ca428 RCX: 0000000000445899
RDX: 0000000000445899 RSI: 00000000000f4240 RDI: 00007f9b5a7c1000
RBP: 00000000004ca420 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000049a074
R13: 00007ffdd09518ef R14: 00007f9b5a7e2400 R15: 0000000000022000
INFO: task syz-executor299:9440 blocked for more than 144 seconds.
Not tainted 5.14.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor299 state:D stack:29184 pid: 9440 ppid: 9439 flags:0x00000000
Call Trace:
context_switch kernel/sched/core.c:4683 [inline]
__schedule+0x93a/0x26f0 kernel/sched/core.c:5940
schedule+0xd3/0x270 kernel/sched/core.c:6019
schedule_timeout+0x1db/0x2a0 kernel/time/timer.c:1854
do_wait_for_common kernel/sched/completion.c:85 [inline]
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common kernel/sched/completion.c:117 [inline]
wait_for_completion+0x176/0x280 kernel/sched/completion.c:138
__do_sys_io_destroy fs/aio.c:1402 [inline]
__se_sys_io_destroy fs/aio.c:1380 [inline]
__x64_sys_io_destroy+0x17e/0x1e0 fs/aio.c:1380
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x445899
RSP: 002b:00007f9b5a7e2318 EFLAGS: 00000246 ORIG_RAX: 00000000000000cf
RAX: ffffffffffffffda RBX: 00000000004ca428 RCX: 0000000000445899
RDX: 0000000000445899 RSI: 0000000000000000 RDI: 00007f9b5a7c1000
RBP: 00000000004ca420 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000049a074
R13: 00007ffdd09518ef R14: 00007f9b5a7e2400 R15: 0000000000022000
INFO: task syz-executor299:9476 blocked for more than 144 seconds.
Not tainted 5.14.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor299 state:D stack:29752 pid: 9476 ppid: 9475 flags:0x00004000
Call Trace:
context_switch kernel/sched/core.c:4683 [inline]
__schedule+0x93a/0x26f0 kernel/sched/core.c:5940
schedule+0xd3/0x270 kernel/sched/core.c:6019
schedule_timeout+0x1db/0x2a0 kernel/time/timer.c:1854
do_wait_for_common kernel/sched/completion.c:85 [inline]
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common kernel/sched/completion.c:117 [inline]
wait_for_completion+0x176/0x280 kernel/sched/completion.c:138
__do_sys_io_destroy fs/aio.c:1402 [inline]
__se_sys_io_destroy fs/aio.c:1380 [inline]
__x64_sys_io_destroy+0x17e/0x1e0 fs/aio.c:1380
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x445899
RSP: 002b:00007f9b5a7e2318 EFLAGS: 00000246 ORIG_RAX: 00000000000000cf
RAX: ffffffffffffffda RBX: 00000000004ca428 RCX: 0000000000445899
RDX: 0000000000445899 RSI: 00000000000f4240 RDI: 00007f9b5a7c1000
RBP: 00000000004ca420 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000049a074
R13: 00007ffdd09518ef R14: 00007f9b5a7e2400 R15: 0000000000022000
INFO: task syz-executor299:9484 blocked for more than 144 seconds.
Not tainted 5.14.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor299 state:D stack:29800 pid: 9484 ppid: 9483 flags:0x00000000
Call Trace:
context_switch kernel/sched/core.c:4683 [inline]
__schedule+0x93a/0x26f0 kernel/sched/core.c:5940
schedule+0xd3/0x270 kernel/sched/core.c:6019
schedule_timeout+0x1db/0x2a0 kernel/time/timer.c:1854
do_wait_for_common kernel/sched/completion.c:85 [inline]
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common kernel/sched/completion.c:117 [inline]
wait_for_completion+0x176/0x280 kernel/sched/completion.c:138
__do_sys_io_destroy fs/aio.c:1402 [inline]
__se_sys_io_destroy fs/aio.c:1380 [inline]
__x64_sys_io_destroy+0x17e/0x1e0 fs/aio.c:1380
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x445899
RSP: 002b:00007f9b5a7e2318 EFLAGS: 00000246 ORIG_RAX: 00000000000000cf
RAX: ffffffffffffffda RBX: 00000000004ca428 RCX: 0000000000445899
RDX: 0000000000445899 RSI: 00000000000f4240 RDI: 00007f9b5a7c1000
RBP: 00000000004ca420 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000049a074
R13: 00007ffdd09518ef R14: 00007f9b5a7e2400 R15: 0000000000022000
INFO: task syz-executor299:9536 blocked for more than 144 seconds.
Not tainted 5.14.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor299 state:D stack:29800 pid: 9536 ppid: 9535 flags:0x00000000
Call Trace:
context_switch kernel/sched/core.c:4683 [inline]
__schedule+0x93a/0x26f0 kernel/sched/core.c:5940
schedule+0xd3/0x270 kernel/sched/core.c:6019
schedule_timeout+0x1db/0x2a0 kernel/time/timer.c:1854
do_wait_for_common kernel/sched/completion.c:85 [inline]
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common kernel/sched/completion.c:117 [inline]
wait_for_completion+0x176/0x280 kernel/sched/completion.c:138
__do_sys_io_destroy fs/aio.c:1402 [inline]
__se_sys_io_destroy fs/aio.c:1380 [inline]
__x64_sys_io_destroy+0x17e/0x1e0 fs/aio.c:1380
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x445899
RSP: 002b:00007f9b5a7e2318 EFLAGS: 00000246 ORIG_RAX: 00000000000000cf
RAX: ffffffffffffffda RBX: 00000000004ca428 RCX: 0000000000445899
RDX: 0000000000445899 RSI: 00000000000f4240 RDI: 00007f9b5a7c1000
RBP: 00000000004ca420 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000049a074
R13: 00007ffdd09518ef R14: 00007f9b5a7e2400 R15: 0000000000022000
INFO: task syz-executor299:9768 blocked for more than 144 seconds.
Not tainted 5.14.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor299 state:D stack:29696 pid: 9768 ppid: 9767 flags:0x00000000
Call Trace:
context_switch kernel/sched/core.c:4683 [inline]
__schedule+0x93a/0x26f0 kernel/sched/core.c:5940
schedule+0xd3/0x270 kernel/sched/core.c:6019
schedule_timeout+0x1db/0x2a0 kernel/time/timer.c:1854
do_wait_for_common kernel/sched/completion.c:85 [inline]
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common kernel/sched/completion.c:117 [inline]
wait_for_completion+0x176/0x280 kernel/sched/completion.c:138
__do_sys_io_destroy fs/aio.c:1402 [inline]
__se_sys_io_destroy fs/aio.c:1380 [inline]
__x64_sys_io_destroy+0x17e/0x1e0 fs/aio.c:1380
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x445899
RSP: 002b:00007f9b5a7e2318 EFLAGS: 00000246 ORIG_RAX: 00000000000000cf
RAX: ffffffffffffffda RBX: 00000000004ca428 RCX: 0000000000445899
RDX: 0000000000445899 RSI: 00000000000f4240 RDI: 00007f9b5a7c1000
RBP: 00000000004ca420 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000049a074
R13: 00007ffdd09518ef R14: 00007f9b5a7e2400 R15: 0000000000022000
INFO: task syz-executor299:9772 blocked for more than 145 seconds.
Not tainted 5.14.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor299 state:D stack:28832 pid: 9772 ppid: 9771 flags:0x00000000
Call Trace:
context_switch kernel/sched/core.c:4683 [inline]
__schedule+0x93a/0x26f0 kernel/sched/core.c:5940
schedule+0xd3/0x270 kernel/sched/core.c:6019
schedule_timeout+0x1db/0x2a0 kernel/time/timer.c:1854
do_wait_for_common kernel/sched/completion.c:85 [inline]
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common kernel/sched/completion.c:117 [inline]
wait_for_completion+0x176/0x280 kernel/sched/completion.c:138
__do_sys_io_destroy fs/aio.c:1402 [inline]
__se_sys_io_destroy fs/aio.c:1380 [inline]
__x64_sys_io_destroy+0x17e/0x1e0 fs/aio.c:1380
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x445899
RSP: 002b:00007f9b5a7e2318 EFLAGS: 00000246 ORIG_RAX: 00000000000000cf
RAX: ffffffffffffffda RBX: 00000000004ca428 RCX: 0000000000445899
RDX: 0000000000445899 RSI: 0000000000000000 RDI: 00007f9b5a7c1000
RBP: 00000000004ca420 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000049a074
R13: 00007ffdd09518ef R14: 00007f9b5a7e2400 R15: 0000000000022000

Showing all locks held in the system:
1 lock held by khungtaskd/1656:
#0: ffffffff8b97b9c0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6446
1 lock held by in:imklog/8155:
#0: ffff888033cdb270 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:974

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

NMI backtrace for cpu 1
CPU: 1 PID: 1656 Comm: khungtaskd Not tainted 5.14.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105
nmi_cpu_backtrace.cold+0x44/0xd7 lib/nmi_backtrace.c:105
nmi_trigger_cpumask_backtrace+0x1b3/0x230 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:210 [inline]
watchdog+0xd0a/0xfc0 kernel/hung_task.c:295
kthread+0x3e5/0x4d0 kernel/kthread.c:319
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4866 Comm: systemd-journal Not tainted 5.14.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:clear_page_erms+0x7/0x10 arch/x86/lib/clear_page_64.S:49
Code: 48 89 47 18 48 89 47 20 48 89 47 28 48 89 47 30 48 89 47 38 48 8d 7f 40 75 d9 90 c3 0f 1f 80 00 00 00 00 b9 00 10 00 00 31 c0 <f3> aa c3 cc cc cc cc cc cc 41 57 41 56 41 55 41 54 55 53 48 89 fb
RSP: 0018:ffffc900015ff850 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffffea0000a365c0 RCX: 00000000000004c0
RDX: 1ffff11005878d15 RSI: 0000000000000008 RDI: ffff888028d97b40
RBP: ffff88802c3c54c0 R08: 0000000000000001 R09: ffffed10051b2000
R10: fffff94000146c86 R11: 0000000000000003 R12: ffffed1005878d69
R13: dffffc0000000000 R14: ffffea0000a36600 R15: ffff88802c3c6b48
FS: 00007fc8b802f8c0(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc8b5421000 CR3: 0000000021001000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
clear_page arch/x86/include/asm/page_64.h:49 [inline]
clear_highpage include/linux/highmem.h:184 [inline]
kernel_init_free_pages.part.0+0x99/0x120 mm/page_alloc.c:1283
kernel_init_free_pages mm/page_alloc.c:1272 [inline]
post_alloc_hook+0x145/0x1e0 mm/page_alloc.c:2423
prep_new_page mm/page_alloc.c:2433 [inline]
get_page_from_freelist+0xa72/0x2f80 mm/page_alloc.c:4166
__alloc_pages+0x1b2/0x500 mm/page_alloc.c:5388
alloc_pages+0x18c/0x2a0 mm/mempolicy.c:2244
alloc_slab_page mm/slub.c:1688 [inline]
allocate_slab+0x32e/0x4b0 mm/slub.c:1828
new_slab mm/slub.c:1891 [inline]
new_slab_objects mm/slub.c:2637 [inline]
___slab_alloc+0x4ba/0x820 mm/slub.c:2800
__slab_alloc.constprop.0+0xa7/0xf0 mm/slub.c:2840
slab_alloc_node mm/slub.c:2922 [inline]
slab_alloc mm/slub.c:2964 [inline]
kmem_cache_alloc+0x3e1/0x4a0 mm/slub.c:2969
getname_flags.part.0+0x50/0x4f0 fs/namei.c:138
getname_flags include/linux/audit.h:319 [inline]
getname+0x8e/0xd0 fs/namei.c:209
do_sys_openat2+0xf5/0x420 fs/open.c:1198
do_sys_open fs/open.c:1220 [inline]
__do_sys_open fs/open.c:1228 [inline]
__se_sys_open fs/open.c:1224 [inline]
__x64_sys_open+0x119/0x1c0 fs/open.c:1224
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7fc8b75be840
Code: 73 01 c3 48 8b 0d 68 77 20 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 89 bb 20 00 00 75 10 b8 02 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 1e f6 ff ff 48 89 04 24
RSP: 002b:00007ffee57eb7d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007ffee57ebae0 RCX: 00007fc8b75be840
RDX: 00000000000001a0 RSI: 0000000000080042 RDI: 0000564a6c2e8060
RBP: 000000000000000d R08: 000000000000c0c1 R09: 00000000ffffffff
R10: 0000000000000069 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000564a6c2da040 R14: 00007ffee57ebaa0 R15: 0000564a6c2e80b0


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[Jeff Moyer]

The reproducer is creating a thread, issuing a IOCB_CMD_PREAD from a
pipe in that thread, and then calling io_destroy from another thread.
Because there is no writer on the other end of the pipe, the read will
block. Note that it also is not submitted asynchronously, as that's not
supported.

io_destroy is "hanging" because it's waiting for the read to finish. If
the read thread is killed, cleanup happens as usual. I'm not sure I
could classify this as a kernel bug.

-Jeff

[Dmitry Vyukov]

Hi Jeff,

Thanks for looking into this. I suspect the reproducer may create a
fork bomb that DoSed the kernel so that it can't make progress for 140
seconds. FTR, I've added it to
https://github.com/google/syzkaller/issues/498#issuecomment-895071514
to take a closer look.

[Jeff Moyer]

No, I described exactly what happens. You can reproduce the hung task
timeout with a much simpler program, attached below.

Cheers,
Jeff

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <libaio.h>
#include <pthread.h>

#define BUFSZ 512

void *
submit_thread(void *arg)
{
io_context_t *ctx = arg;
int ret;
int fds[2];
char buf[BUFSZ];
struct iocb iocb, *iocbp = &iocb;

ret = pipe(fds);
if (ret) {
perror("pipe");
exit(1);
}

io_prep_pread(iocbp, fds[0], buf, BUFSZ, 0);

ret = io_submit(*ctx, 1, &iocbp);
if (ret != 1) {
printf("io_submit failed with %d\n", ret);
exit(1);
}

/* NOTREACHED */
printf("Read submitted.\n");
return 0;
}

int
main(void)
{
int ret;
io_context_t ctx;
pthread_t pth;

memset(&ctx, 0, sizeof(ctx));
ret = io_setup(1, &ctx);
if (ret) {
printf("io_setup failed with %d\n", ret);
exit(1);
}

ret = pthread_create(&pth, NULL, submit_thread, &ctx);
if (ret) {
perror("pthread_create");
exit(1);
}

usleep(1000); /* give the thread time to run */

ret = io_destroy(ctx);
if (ret) {
printf("io_destroy failed with %d\n", ret);
exit(1);
}

exit(0);
}

[Dmitry Vyukov]

Ah, I see.
But then shouldn't any userspace program be able to trigger kernel bug
detection splats? If userspace programs can trigger bug detection
warnings "legitimately", it makes it impossible to use these bug
detection facilities in kernel testing.
Also the reproducer should have killed the child process much sooner
than 140 second, why did it still produce the warning?
Also I wonder if it's possible to deadlock the system by creating 2
tasks each waiting on the other, and both becoming non-killable as the
result (maybe playing with CLONE_THREAD/VM)?