[syzbot] [fs?] INFO: task hung in eventpoll_release_file

syzbot
2023-03-20T21:06:57Z

Hello,

syzbot found the following issue on:

HEAD commit: 6f72958a49f6 Add linux-next specific files for 20230316
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=178faee6c80000
kernel config: https://syzkaller.appspot.com/x/.config?x=dd64232230d3a0d8
dashboard link: https://syzkaller.appspot.com/bug?extid=e6dab35a08df7f7aa260
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1156a6ecc80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=179e9648c80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/3fcac83e3d53/disk-6f72958a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/37b457d3103a/vmlinux-6f72958a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b82735625cce/bzImage-6f72958a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e6dab35a08df7f7aa260@syzkaller.appspotmail.com

INFO: task syz-executor397:5874 blocked for more than 143 seconds.
Not tainted 6.3.0-rc2-next-20230316-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor397 state:D stack:27072 pid:5874 ppid:5147 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5305 [inline]
__schedule+0x1d23/0x5650 kernel/sched/core.c:6623
schedule+0xde/0x1a0 kernel/sched/core.c:6699
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6758
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0xa3b/0x1350 kernel/locking/mutex.c:747
eventpoll_release_file+0xe2/0x1d0 fs/eventpoll.c:962
eventpoll_release include/linux/eventpoll.h:53 [inline]
__fput+0x7da/0xa90 fs/file_table.c:312
task_work_run+0x16f/0x270 kernel/task_work.c:179
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
exit_to_user_mode_prepare+0x210/0x240 kernel/entry/common.c:204
__syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:297
do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f0183a1b0b9
RSP: 002b:00007f01831bf208 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: 0000000000000116 RBX: 00007f0183a9d4a8 RCX: 00007f0183a1b0b9
RDX: 0000000000000318 RSI: 00000000200bd000 RDI: 0000000000000004
RBP: 00007f0183a9d4a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f0183a9d4ac
R13: 00007fff8a59281f R14: 00007f01831bf300 R15: 0000000000022000
</TASK>

Showing all locks held in the system:
1 lock held by rcu_tasks_kthre/13:
#0: ffffffff8c795830 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x31/0xd80 kernel/rcu/tasks.h:516
1 lock held by rcu_tasks_trace/14:
#0: ffffffff8c795530 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x31/0xd80 kernel/rcu/tasks.h:516
1 lock held by khungtaskd/28:
#0: ffffffff8c796400 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x390 kernel/locking/lockdep.c:6545
2 locks held by getty/4761:
#0: ffff88814a34b098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x26/0x80 drivers/tty/tty_ldisc.c:243
#1: ffffc900015902f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0xef4/0x13e0 drivers/tty/n_tty.c:2177
1 lock held by syz-executor397/5873:
1 lock held by syz-executor397/5874:
#0: ffff88801e3d5c68 (&ep->mtx){+.+.}-{3:3}, at: eventpoll_release_file+0xe2/0x1d0 fs/eventpoll.c:962

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

NMI backtrace for cpu 0
CPU: 0 PID: 28 Comm: khungtaskd Not tainted 6.3.0-rc2-next-20230316-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
nmi_cpu_backtrace+0x29c/0x350 lib/nmi_backtrace.c:113
nmi_trigger_cpumask_backtrace+0x2a4/0x300 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline]
watchdog+0xe16/0x1090 kernel/hung_task.c:379
kthread+0x33e/0x440 kernel/kthread.c:379
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 5873 Comm: syz-executor397 Not tainted 6.3.0-rc2-next-20230316-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
RIP: 0010:arch_atomic_read arch/x86/include/asm/atomic.h:29 [inline]
RIP: 0010:rcu_dynticks_curr_cpu_in_eqs include/linux/context_tracking.h:121 [inline]
RIP: 0010:rcu_is_watching+0x47/0xb0 kernel/rcu/tree.c:695
Code: c5 77 7a 48 8d 3c ed 00 fa 10 8c 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 75 54 48 03 1c ed 00 fa 10 8c <48> b8 00 00 00 00 00 fc ff df 48 89 da 48 c1 ea 03 0f b6 14 02 48
RSP: 0018:ffffc90004c9fc58 EFLAGS: 00000282
RAX: dffffc0000000000 RBX: ffff8880b9936c68 RCX: ffffffff8164cf65
RDX: 1ffffffff1821f41 RSI: 0000000000000002 RDI: ffffffff8c10fa08
RBP: 0000000000000001 R08: 0000000000000000 R09: ffffffff8e784717
R10: fffffbfff1cf08e2 R11: 0000000000000000 R12: ffff8880772cf1c8
R13: ffff88801e3d5c00 R14: ffff8880772cf180 R15: 0000000000000000
FS: 0000555556477400(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005642a1c9c5c0 CR3: 0000000025100000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
trace_lock_release include/trace/events/lock.h:69 [inline]
lock_release+0x4fb/0x670 kernel/locking/lockdep.c:5702
__raw_spin_unlock include/linux/spinlock_api_smp.h:141 [inline]
_raw_spin_unlock+0x16/0x40 kernel/locking/spinlock.c:186
spin_unlock include/linux/spinlock.h:390 [inline]
__ep_remove+0x6ce/0xa50 fs/eventpoll.c:737
ep_remove_safe fs/eventpoll.c:782 [inline]
ep_clear_and_put+0x21c/0x3b0 fs/eventpoll.c:815
ep_eventpoll_release+0x45/0x60 fs/eventpoll.c:831
__fput+0x27c/0xa90 fs/file_table.c:321
task_work_run+0x16f/0x270 kernel/task_work.c:179
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
exit_to_user_mode_prepare+0x210/0x240 kernel/entry/common.c:204
__syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:297
do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f01839d3dfb
Code: 0f 05 48 3d 00 f0 ff ff 77 45 c3 0f 1f 40 00 48 83 ec 18 89 7c 24 0c e8 63 fc ff ff 8b 7c 24 0c 41 89 c0 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 44 89 c7 89 44 24 0c e8 a1 fc ff ff 8b 44
RSP: 002b:00007fff8a592880 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000006 RCX: 00007f01839d3dfb
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 0000000000152fad R08: 0000000000000000 R09: 00007fff8a5a7080
R10: 0000000000000000 R11: 0000000000000293 R12: 00007f0183a9d4bc
R13: 00007fff8a592900 R14: 00007fff8a5929a0 R15: 00007f0183a9d4a0
</TASK>

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