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Subject: Re: [syzbot] INFO: task hung in io_uring_cancel_generic
To:     syzbot <syzbot+ba6fcd859210f4e9e109@syzkaller.appspotmail.com>,
        axboe@kernel.dk, io-uring@vger.kernel.org,
        linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com
References: <0000000000003f0feb05c6daa326@google.com>
From:   Pavel Begunkov <asml.silence@gmail.com>
Message-ID: <abb0b94a-1bfb-1fe4-06fc-daed6c0112b6@gmail.com>
Date:   Sun, 11 Jul 2021 21:20:31 +0100
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On 7/11/21 4:27 PM, syzbot wrote:
> Hello,
> 
> syzbot has tested the proposed patch but the reproducer is still triggering an issue:
> INFO: task hung in io_uring_cancel_generic

I think I see what it is. To not duplicate efforts...

> 
> INFO: task syz-executor.5:10156 blocked for more than 143 seconds.
>       Tainted: G        W         5.13.0-syzkaller #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz-executor.5  state:D stack:27976 pid:10156 ppid:  8832 flags:0x00004004
> Call Trace:
>  context_switch kernel/sched/core.c:4683 [inline]
>  __schedule+0x934/0x2710 kernel/sched/core.c:5940
>  schedule+0xd3/0x270 kernel/sched/core.c:6019
>  io_uring_cancel_generic+0x54d/0x890 fs/io_uring.c:9148
>  io_uring_files_cancel include/linux/io_uring.h:16 [inline]
>  do_exit+0x28b/0x2a50 kernel/exit.c:780
>  do_group_exit+0x125/0x310 kernel/exit.c:922
>  get_signal+0x47f/0x2150 kernel/signal.c:2796
>  arch_do_signal_or_restart+0x2a9/0x1eb0 arch/x86/kernel/signal.c:789
>  handle_signal_work kernel/entry/common.c:148 [inline]
>  exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
>  exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:209
>  __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
>  syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:302
>  do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x4665d9
> RSP: 002b:00007fc32f0d4218 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
> RAX: fffffffffffffe00 RBX: 000000000056bf88 RCX: 00000000004665d9
> RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000056bf88
> RBP: 000000000056bf80 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf8c
> R13: 00007ffee94563df R14: 00007fc32f0d4300 R15: 0000000000022000
> INFO: task syz-executor.2:10228 blocked for more than 143 seconds.
>       Tainted: G        W         5.13.0-syzkaller #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz-executor.2  state:D stack:29192 pid:10228 ppid:  8825 flags:0x00004004
> Call Trace:
>  context_switch kernel/sched/core.c:4683 [inline]
>  __schedule+0x934/0x2710 kernel/sched/core.c:5940
>  schedule+0xd3/0x270 kernel/sched/core.c:6019
>  io_uring_cancel_generic+0x54d/0x890 fs/io_uring.c:9148
>  io_uring_files_cancel include/linux/io_uring.h:16 [inline]
>  do_exit+0x28b/0x2a50 kernel/exit.c:780
>  do_group_exit+0x125/0x310 kernel/exit.c:922
>  get_signal+0x47f/0x2150 kernel/signal.c:2796
>  arch_do_signal_or_restart+0x2a9/0x1eb0 arch/x86/kernel/signal.c:789
>  handle_signal_work kernel/entry/common.c:148 [inline]
>  exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
>  exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:209
>  __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
>  syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:302
>  do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x4665d9
> RSP: 002b:00007f48eed2e218 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
> RAX: 0000000000000000 RBX: 000000000056bf88 RCX: 00000000004665d9
> RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000056bf88
> RBP: 000000000056bf80 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf8c
> R13: 00007ffc352d975f R14: 00007f48eed2e300 R15: 0000000000022000
> INFO: task syz-executor.3:10229 blocked for more than 143 seconds.
>       Tainted: G        W         5.13.0-syzkaller #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz-executor.3  state:D stack:27976 pid:10229 ppid:  8828 flags:0x00004004
> Call Trace:
>  context_switch kernel/sched/core.c:4683 [inline]
>  __schedule+0x934/0x2710 kernel/sched/core.c:5940
>  schedule+0xd3/0x270 kernel/sched/core.c:6019
>  io_uring_cancel_generic+0x54d/0x890 fs/io_uring.c:9148
>  io_uring_files_cancel include/linux/io_uring.h:16 [inline]
>  do_exit+0x28b/0x2a50 kernel/exit.c:780
>  do_group_exit+0x125/0x310 kernel/exit.c:922
>  get_signal+0x47f/0x2150 kernel/signal.c:2796
>  arch_do_signal_or_restart+0x2a9/0x1eb0 arch/x86/kernel/signal.c:789
>  handle_signal_work kernel/entry/common.c:148 [inline]
>  exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
>  exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:209
>  __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
>  syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:302
>  do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x4665d9
> RSP: 002b:00007fb1b5eac218 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
> RAX: 0000000000000000 RBX: 000000000056bf88 RCX: 00000000004665d9
> RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000056bf88
> RBP: 000000000056bf80 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf8c
> R13: 00007ffdb651a9bf R14: 00007fb1b5eac300 R15: 0000000000022000
> INFO: task syz-executor.0:10241 blocked for more than 144 seconds.
>       Tainted: G        W         5.13.0-syzkaller #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz-executor.0  state:D stack:27976 pid:10241 ppid:  8830 flags:0x00004004
> Call Trace:
>  context_switch kernel/sched/core.c:4683 [inline]
>  __schedule+0x934/0x2710 kernel/sched/core.c:5940
>  schedule+0xd3/0x270 kernel/sched/core.c:6019
>  io_uring_cancel_generic+0x54d/0x890 fs/io_uring.c:9148
>  io_uring_files_cancel include/linux/io_uring.h:16 [inline]
>  do_exit+0x28b/0x2a50 kernel/exit.c:780
>  do_group_exit+0x125/0x310 kernel/exit.c:922
>  get_signal+0x47f/0x2150 kernel/signal.c:2796
>  arch_do_signal_or_restart+0x2a9/0x1eb0 arch/x86/kernel/signal.c:789
>  handle_signal_work kernel/entry/common.c:148 [inline]
>  exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
>  exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:209
>  __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
>  syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:302
>  do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x4665d9
> RSP: 002b:00007fa3ce68b218 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
> RAX: 0000000000000000 RBX: 000000000056bf88 RCX: 00000000004665d9
> RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000056bf88
> RBP: 000000000056bf80 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf8c
> R13: 00007ffcf35d4ebf R14: 00007fa3ce68b300 R15: 0000000000022000
> INFO: task syz-executor.1:10247 blocked for more than 144 seconds.
>       Tainted: G        W         5.13.0-syzkaller #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz-executor.1  state:D stack:27976 pid:10247 ppid:  8831 flags:0x00004004
> Call Trace:
>  context_switch kernel/sched/core.c:4683 [inline]
>  __schedule+0x934/0x2710 kernel/sched/core.c:5940
>  schedule+0xd3/0x270 kernel/sched/core.c:6019
>  io_uring_cancel_generic+0x54d/0x890 fs/io_uring.c:9148
>  io_uring_files_cancel include/linux/io_uring.h:16 [inline]
>  do_exit+0x28b/0x2a50 kernel/exit.c:780
>  do_group_exit+0x125/0x310 kernel/exit.c:922
>  get_signal+0x47f/0x2150 kernel/signal.c:2796
>  arch_do_signal_or_restart+0x2a9/0x1eb0 arch/x86/kernel/signal.c:789
>  handle_signal_work kernel/entry/common.c:148 [inline]
>  exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
>  exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:209
>  __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
>  syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:302
>  do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x4665d9
> RSP: 002b:00007f7c4a218218 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
> RAX: 0000000000000000 RBX: 000000000056bf88 RCX: 00000000004665d9
> RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000056bf88
> RBP: 000000000056bf80 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf8c
> R13: 00007ffdaa7cc7af R14: 00007f7c4a218300 R15: 0000000000022000
> INFO: task syz-executor.4:10271 blocked for more than 144 seconds.
>       Tainted: G        W         5.13.0-syzkaller #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz-executor.4  state:D stack:27976 pid:10271 ppid:  8827 flags:0x00004004
> Call Trace:
>  context_switch kernel/sched/core.c:4683 [inline]
>  __schedule+0x934/0x2710 kernel/sched/core.c:5940
>  schedule+0xd3/0x270 kernel/sched/core.c:6019
>  io_uring_cancel_generic+0x54d/0x890 fs/io_uring.c:9148
>  io_uring_files_cancel include/linux/io_uring.h:16 [inline]
>  do_exit+0x28b/0x2a50 kernel/exit.c:780
>  do_group_exit+0x125/0x310 kernel/exit.c:922
>  get_signal+0x47f/0x2150 kernel/signal.c:2796
>  arch_do_signal_or_restart+0x2a9/0x1eb0 arch/x86/kernel/signal.c:789
>  handle_signal_work kernel/entry/common.c:148 [inline]
>  exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
>  exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:209
>  __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
>  syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:302
>  do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x4665d9
> RSP: 002b:00007fcb3ff30218 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
> RAX: 0000000000000000 RBX: 000000000056bf88 RCX: 00000000004665d9
> RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000056bf88
> RBP: 000000000056bf80 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf8c
> R13: 00007ffd6fb6745f R14: 00007fcb3ff30300 R15: 0000000000022000
> INFO: lockdep is turned off.
> NMI backtrace for cpu 1
> CPU: 1 PID: 1635 Comm: khungtaskd Tainted: G        W         5.13.0-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:79 [inline]
>  dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:96
>  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:209 [inline]
>  watchdog+0xd4b/0xfb0 kernel/hung_task.c:294
>  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: 8 Comm: kworker/0:2 Tainted: G        W         5.13.0-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Workqueue: events_power_efficient toggle_allocation_gate
> RIP: 0010:__kasan_check_read+0x4/0x10 mm/kasan/shadow.c:31
> Code: 24 07 48 85 db 0f 85 f6 0d 26 07 48 83 c4 60 5b 5d 41 5c 41 5d c3 c3 e9 f6 0e 26 07 cc cc cc cc cc cc cc cc cc cc 48 8b 0c 24 <89> f6 31 d2 e9 03 f9 ff ff 0f 1f 00 48 8b 0c 24 89 f6 ba 01 00 00
> RSP: 0018:ffffc90000cd79a8 EFLAGS: 00000046
> RAX: 0000000000000001 RBX: ffff888140158660 RCX: ffffffff81347c5f
> RDX: ffffed102802b0cd RSI: 0000000000000008 RDI: ffffffff8baa4870
> RBP: ffffffff8baa4460 R08: 0000000000000001 R09: ffff888140158667
> R10: ffffed102802b0cc R11: 000000000000003f R12: ffff888140158000
> R13: ffffffff8baa4870 R14: ffff888140158660 R15: ffffffff8baa4400
> FS:  0000000000000000(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f089e135020 CR3: 000000013fe38000 CR4: 0000000000350ef0
> Call Trace:
>  instrument_atomic_read include/linux/instrumented.h:71 [inline]
>  atomic64_read include/asm-generic/atomic-instrumented.h:605 [inline]
>  switch_mm_irqs_off+0x1df/0x9b0 arch/x86/mm/tlb.c:556
>  unuse_temporary_mm arch/x86/kernel/alternative.c:763 [inline]
>  __text_poke+0x541/0x8c0 arch/x86/kernel/alternative.c:859
>  text_poke_bp_batch+0x3d7/0x560 arch/x86/kernel/alternative.c:1178
>  text_poke_flush arch/x86/kernel/alternative.c:1268 [inline]
>  text_poke_flush arch/x86/kernel/alternative.c:1265 [inline]
>  text_poke_finish+0x16/0x30 arch/x86/kernel/alternative.c:1275
>  arch_jump_label_transform_apply+0x13/0x20 arch/x86/kernel/jump_label.c:145
>  jump_label_update+0x1d5/0x430 kernel/jump_label.c:827
>  static_key_enable_cpuslocked+0x1b1/0x260 kernel/jump_label.c:177
>  static_key_enable+0x16/0x20 kernel/jump_label.c:190
>  toggle_allocation_gate mm/kfence/core.c:623 [inline]
>  toggle_allocation_gate+0x100/0x390 mm/kfence/core.c:615
>  process_one_work+0x98d/0x1630 kernel/workqueue.c:2276
>  worker_thread+0x658/0x11f0 kernel/workqueue.c:2422
>  kthread+0x3e5/0x4d0 kernel/kthread.c:319
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
> 
> 
> Tested on:
> 
> commit:         dfa01077 io_uring: use right task for exiting checks
> git tree:       git://git.kernel.dk/linux-block io_uring-5.14-test
> console output: https://syzkaller.appspot.com/x/log.txt?x=13b501e2300000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=c650d78cfe48974c
> dashboard link: https://syzkaller.appspot.com/bug?extid=ba6fcd859210f4e9e109
> compiler:       
> 

-- 
Pavel Begunkov