INFO: task can't die in pipe_release

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    01830e6c Add linux-next specific files for 20200731
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=161d1214900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2e226b2d1364112c
dashboard link: https://syzkaller.appspot.com/bug?extid=e9a0f7eeac6eb345692d
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16441648900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e9a0f7eeac6eb345692d@xxxxxxxxxxxxxxxxxxxxxxxxx

INFO: task syz-executor.0:7667 can't die for more than 143 seconds.
syz-executor.0  D28360  7667   6876 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:3669 [inline]
 __schedule+0x8e5/0x21e0 kernel/sched/core.c:4418
 schedule+0xd0/0x2a0 kernel/sched/core.c:4493
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:4552
 __mutex_lock_common kernel/locking/mutex.c:1033 [inline]
 __mutex_lock+0x3e2/0x10e0 kernel/locking/mutex.c:1103
 __pipe_lock fs/pipe.c:87 [inline]
 pipe_release+0x49/0x320 fs/pipe.c:722
 __fput+0x285/0x920 fs/file_table.c:281
 task_work_run+0xdd/0x190 kernel/task_work.c:135
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:139 [inline]
 exit_to_user_mode_prepare+0x195/0x1c0 kernel/entry/common.c:166
 syscall_exit_to_user_mode+0x59/0x2b0 kernel/entry/common.c:241
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x416791
Code: Bad RIP value.
RSP: 002b:00007ffd7aff1510 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000007 RCX: 0000000000416791
RDX: 0000000000000000 RSI: 00000000007904d0 RDI: 0000000000000006
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 00007ffd7aff1600 R11: 0000000000000293 R12: 00000000007905a8
R13: 000000000010297d R14: ffffffffffffffff R15: 000000000078bfac
INFO: task syz-executor.0:7667 blocked for more than 143 seconds.
      Not tainted 5.8.0-rc7-next-20200731-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.0  D28360  7667   6876 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:3669 [inline]
 __schedule+0x8e5/0x21e0 kernel/sched/core.c:4418
 schedule+0xd0/0x2a0 kernel/sched/core.c:4493
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:4552
 __mutex_lock_common kernel/locking/mutex.c:1033 [inline]
 __mutex_lock+0x3e2/0x10e0 kernel/locking/mutex.c:1103
 __pipe_lock fs/pipe.c:87 [inline]
 pipe_release+0x49/0x320 fs/pipe.c:722
 __fput+0x285/0x920 fs/file_table.c:281
 task_work_run+0xdd/0x190 kernel/task_work.c:135
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:139 [inline]
 exit_to_user_mode_prepare+0x195/0x1c0 kernel/entry/common.c:166
 syscall_exit_to_user_mode+0x59/0x2b0 kernel/entry/common.c:241
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x416791
Code: Bad RIP value.
RSP: 002b:00007ffd7aff1510 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000007 RCX: 0000000000416791
RDX: 0000000000000000 RSI: 00000000007904d0 RDI: 0000000000000006
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 00007ffd7aff1600 R11: 0000000000000293 R12: 00000000007905a8
R13: 000000000010297d R14: ffffffffffffffff R15: 000000000078bfac
INFO: task syz-executor.0:7670 can't die for more than 143 seconds.
syz-executor.0  R  running task    28640  7670   6876 0x00004006
Call Trace:

Showing all locks held in the system:
1 lock held by khungtaskd/1166:
 #0: ffffffff89c52a80 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:5823
1 lock held by in:imklog/6548:
 #0: ffff8880a78ff6b0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:930
1 lock held by syz-executor.0/7667:
 #0: ffff888095b17068 (&pipe->mutex/1){+.+.}-{3:3}, at: __pipe_lock fs/pipe.c:87 [inline]
 #0: ffff888095b17068 (&pipe->mutex/1){+.+.}-{3:3}, at: pipe_release+0x49/0x320 fs/pipe.c:722
2 locks held by syz-executor.0/7670:

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

NMI backtrace for cpu 0
CPU: 0 PID: 1166 Comm: khungtaskd Not tainted 5.8.0-rc7-next-20200731-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+0x18f/0x20d lib/dump_stack.c:118
 nmi_cpu_backtrace.cold+0x44/0xd7 lib/nmi_backtrace.c:105
 nmi_trigger_cpumask_backtrace+0x1b3/0x223 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:147 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:253 [inline]
 watchdog+0xd89/0xf30 kernel/hung_task.c:339
 kthread+0x3b5/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 7670 Comm: syz-executor.0 Not tainted 5.8.0-rc7-next-20200731-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:preempt_count arch/x86/include/asm/preempt.h:26 [inline]
RIP: 0010:check_kcov_mode kernel/kcov.c:163 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x9/0x60 kernel/kcov.c:197
Code: 5d be 03 00 00 00 e9 a6 06 27 02 66 0f 1f 44 00 00 48 8b be b0 01 00 00 e8 b4 ff ff ff 31 c0 c3 90 65 48 8b 14 25 c0 fe 01 00 <65> 8b 05 60 be 8d 7e a9 00 01 ff 00 48 8b 34 24 74 0f f6 c4 01 74
RSP: 0018:ffffc9000810f8c8 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff83996704
RDX: ffff888099a02400 RSI: ffff888099a02400 RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000000000 R09: ffff888098fb63c7
R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
R13: ffffc9000810fcd0 R14: dffffc0000000000 R15: ffff88808a07c800
FS:  00007f1f60805700(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055d76e4bd938 CR3: 00000000a8964000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 iov_iter_alignment+0x4c2/0x850 lib/iov_iter.c:1237
 ext4_unaligned_io fs/ext4/file.c:175 [inline]
 ext4_dio_write_iter fs/ext4/file.c:465 [inline]
 ext4_file_write_iter+0x345/0x1390 fs/ext4/file.c:655
 call_write_iter include/linux/fs.h:1876 [inline]
 do_iter_readv_writev+0x567/0x780 fs/read_write.c:730
 do_iter_write+0x188/0x670 fs/read_write.c:1035
 vfs_iter_write+0x70/0xa0 fs/read_write.c:1076
 iter_file_splice_write+0x721/0xbe0 fs/splice.c:667
 do_splice_from fs/splice.c:736 [inline]
 do_splice+0xbb8/0x17a0 fs/splice.c:1043
 __do_sys_splice fs/splice.c:1318 [inline]
 __se_sys_splice fs/splice.c:1300 [inline]
 __x64_sys_splice+0x198/0x250 fs/splice.c:1300
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45cc79
Code: 2d b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 fb b5 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f1f60804c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 0000000000032b80 RCX: 000000000045cc79
RDX: 0000000000000003 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 000000000078bff8 R08: 000000000000ffe0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078bfac
R13: 00007ffd7aff149f R14: 00007f1f608059c0 R15: 000000000078bfac


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