INFO: task hung in pipe_write

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 693bea3a BACKPORT: PM/sleep: Expose suspend stats in sysfs
git tree: android-4.14
console output: https://syzkaller.appspot.com/x/log.txt?x=167c4f9f600000
kernel config: https://syzkaller.appspot.com/x/.config?x=1dc5f9f3c6cda16c
dashboard link: https://syzkaller.appspot.com/bug?extid=4060e186478220210007
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+4060e1...@syzkaller.appspotmail.com

SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0
sclass=netlink_route_socket pig=6975 comm=syz-executor.4
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=3
sclass=netlink_route_socket pig=6974 comm=syz-executor.4
INFO: task syz-executor.2:6939 blocked for more than 140 seconds.
Not tainted 4.14.149+ #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.2 D26384 6939 1841 0x00000004
Call Trace:
schedule+0x92/0x1c0 kernel/sched/core.c:3498
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3556
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x595/0x13e0 kernel/locking/mutex.c:893
pipe_lock_nested fs/pipe.c:67 [inline]
pipe_lock fs/pipe.c:75 [inline]
pipe_wait+0x1a1/0x1c0 fs/pipe.c:123
pipe_write+0x510/0xe20 fs/pipe.c:490
call_write_iter include/linux/fs.h:1798 [inline]
new_sync_write fs/read_write.c:471 [inline]
__vfs_write+0x401/0x5a0 fs/read_write.c:484
vfs_write+0x17f/0x4d0 fs/read_write.c:546
SYSC_write fs/read_write.c:594 [inline]
SyS_write+0x102/0x250 fs/read_write.c:586
do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x459a59
RSP: 002b:00007f3a8dba1c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459a59
RDX: 000000010000014c RSI: 0000000020000340 RDI: 0000000000000006
RBP: 000000000075c070 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f3a8dba26d4
R13: 00000000004c6229 R14: 00000000004e0cc8 R15: 00000000ffffffff

Showing all locks held in the system:
1 lock held by khungtaskd/23:
#0: (tasklist_lock){.+.+}, at: [<000000001db7b752>]
debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4544
2 locks held by getty/1760:
#0: (&tty->ldisc_sem){++++}, at: [<00000000061d9d74>]
tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
#1: (&ldata->atomic_read_lock){+.+.}, at: [<000000007b98c8e5>]
n_tty_read+0x1f7/0x1700 drivers/tty/n_tty.c:2156
1 lock held by syz-executor.2/6939:
#0: (&pipe->mutex/1){+.+.}, at: [<00000000aa21e6d3>] pipe_lock_nested
fs/pipe.c:67 [inline]
#0: (&pipe->mutex/1){+.+.}, at: [<00000000aa21e6d3>] pipe_lock
fs/pipe.c:75 [inline]
#0: (&pipe->mutex/1){+.+.}, at: [<00000000aa21e6d3>]
pipe_wait+0x1a1/0x1c0 fs/pipe.c:123

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

NMI backtrace for cpu 1
CPU: 1 PID: 23 Comm: khungtaskd Not tainted 4.14.149+ #0
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0xca/0x134 lib/dump_stack.c:53
nmi_cpu_backtrace.cold+0x47/0x86 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x119/0x147 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:140 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:195 [inline]
watchdog+0x629/0xbe0 kernel/hung_task.c:274
kthread+0x31f/0x430 kernel/kthread.c:232
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:404
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 6973 Comm: syz-executor.2 Not tainted 4.14.149+ #0
task: 00000000ada2d4e6 task.stack: 00000000e727044c
RIP: 0010:__sanitizer_cov_trace_pc+0x23/0x60 kernel/kcov.c:68
RSP: 0018:ffff8881a0597628 EFLAGS: 00000246
RAX: ffff8881d2cfde00 RBX: 00000000000001a0 RCX: 0000000000040000
RDX: 0000000000000001 RSI: ffffc90001b9c000 RDI: ffffea00065f88d0
RBP: ffffea00065f88c0 R08: 00000000000022c9 R09: 0000000000000003
R10: ffff8881d2cfe6a8 R11: 928889ff0c4961c5 R12: ffff88819a5652e0
R13: ffffffff83b5a2c0 R14: 00000000fffffff2 R15: ffff8881d594d500
FS: 00007f3a8db3f700(0000) GS:ffff8881dba00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000201a0500 CR3: 000000019ee56003 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
block_page_mkwrite+0x132/0x2b0 fs/buffer.c:2550
ext4_page_mkwrite+0xd81/0x1030 fs/ext4/inode.c:6158
do_page_mkwrite+0xd9/0x2f0 mm/memory.c:2383
wp_page_shared mm/memory.c:2675 [inline]
do_wp_page+0x858/0x19d0 mm/memory.c:2775
handle_pte_fault mm/memory.c:4005 [inline]
__handle_mm_fault+0xdec/0x2700 mm/memory.c:4113
handle_mm_fault+0x3c3/0x6da mm/memory.c:4150
__do_page_fault+0x477/0xbb0 arch/x86/mm/fault.c:1420
page_fault+0x22/0x50 arch/x86/entry/entry_64.S:1122
RIP: 0010:copy_user_enhanced_fast_string+0x7/0x10
arch/x86/lib/copy_user_64.S:181
RSP: 0018:ffff8881a0597b58 EFLAGS: 00010206
RAX: 0000000000000000 RBX: 0000000000001000 RCX: 0000000000001000
RDX: 0000000000001000 RSI: ffff8881a0bdf000 RDI: 00000000201a0500
RBP: 00000000201a0500 R08: ffffed103417c000 R09: 0000000000000000
R10: ffffed103417bfff R11: ffff8881a0bdffff R12: ffff8881a0bdf000
R13: 00007ffffffff000 R14: 00000000201a1500 R15: ffff8881a0597dd0
copy_user_generic arch/x86/include/asm/uaccess_64.h:37 [inline]
raw_copy_to_user arch/x86/include/asm/uaccess_64.h:112 [inline]
copyout+0x99/0xc0 lib/iov_iter.c:137
copy_page_to_iter_iovec lib/iov_iter.c:206 [inline]
copy_page_to_iter+0x367/0xd50 lib/iov_iter.c:723
pipe_to_user+0xa8/0x160 fs/splice.c:1237
splice_from_pipe_feed fs/splice.c:502 [inline]
__splice_from_pipe+0x331/0x740 fs/splice.c:626
vmsplice_to_user+0x1bd/0x1e0 fs/splice.c:1272
SYSC_vmsplice fs/splice.c:1353 [inline]
SyS_vmsplice+0x12a/0x150 fs/splice.c:1334
do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x459a59
RSP: 002b:00007f3a8db3ec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000116
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000459a59
RDX: 0000000000000001 RSI: 0000000020000000 RDI: 0000000000000005
RBP: 000000000075c268 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f3a8db3f6d4
R13: 00000000004c94e5 R14: 00000000004e0c68 R15: 00000000ffffffff
Code: 00 00 e9 90 ed ff ff 90 65 48 8b 04 25 c0 de 01 00 48 85 c0 74 1a 65
8b 15 bb bc 90 7c 81 e2 00 01 1f 00 75 0b 8b 90 a8 11 00 00 <83> fa 01 74
01 c3 48 c7 c2 00 00 00 81 48 81 ea 00 00 40 83 48


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.