INFO: task hung in blkdev_put

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 58b454eb Linux 4.14.112
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=12594d8f200000
kernel config: https://syzkaller.appspot.com/x/.config?x=8b0e7ab7678533ab
dashboard link: https://syzkaller.appspot.com/bug?extid=8fcb28f1e98b73e71986
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+8fcb28...@syzkaller.appspotmail.com

loop0: p10 start 1024196688 is beyond EOD, truncated
loop0: p11 start 889836404 is beyond EOD, truncated
loop0: p12 start 1272861677 is beyond EOD, truncated
audit: type=1400 audit(1555525021.602:56): avc: denied { map } for
pid=9228 comm="sh" path="/bin/dash" dev="sda1" ino=1473
scontext=system_u:system_r:insmod_t:s0-s0:c0.c1023
tcontext=system_u:object_r:file_t:s0 tclass=file permissive=1
INFO: task syz-executor.1:7105 blocked for more than 140 seconds.
Not tainted 4.14.112 #2
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.1 D24992 7105 1 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2807 [inline]
__schedule+0x7be/0x1cf0 kernel/sched/core.c:3383
schedule+0x92/0x1c0 kernel/sched/core.c:3427
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3485
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x73c/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
blkdev_put+0x2b/0x510 fs/block_dev.c:1814
blkdev_close+0x8b/0xb0 fs/block_dev.c:1863
__fput+0x277/0x7a0 fs/file_table.c:210
____fput+0x16/0x20 fs/file_table.c:244
task_work_run+0x119/0x190 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1da/0x220 arch/x86/entry/common.c:163
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:267 [inline]
do_syscall_64+0x4a9/0x630 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x4129c0
RSP: 002b:00007ffe06877dd8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 00000000004129c0
RDX: 0000000000000000 RSI: 0000000000004c01 RDI: 0000000000000003
RBP: 00000000000000b7 R08: 0000000000000000 R09: 000000000000000a
R10: 0000000000000075 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffe06877e10 R14: 0000000000033d21 R15: 00007ffe06877e20
INFO: task syz-executor.2:7107 blocked for more than 140 seconds.
Not tainted 4.14.112 #2
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.2 D24992 7107 1 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2807 [inline]
__schedule+0x7be/0x1cf0 kernel/sched/core.c:3383
schedule+0x92/0x1c0 kernel/sched/core.c:3427
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3485
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x73c/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
blkdev_put+0x2b/0x510 fs/block_dev.c:1814
blkdev_close+0x8b/0xb0 fs/block_dev.c:1863
__fput+0x277/0x7a0 fs/file_table.c:210
____fput+0x16/0x20 fs/file_table.c:244
task_work_run+0x119/0x190 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1da/0x220 arch/x86/entry/common.c:163
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:267 [inline]
do_syscall_64+0x4a9/0x630 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x4129c0
RSP: 002b:00007ffccb1a94e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 00000000004129c0
RDX: 0000000000000000 RSI: 0000000000004c01 RDI: 0000000000000003
RBP: 00000000000000c6 R08: 0000000000000000 R09: 000000000000000a
R10: 0000000000000075 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffccb1a9520 R14: 0000000000033d21 R15: 00007ffccb1a9530
INFO: task syz-executor.3:7108 blocked for more than 140 seconds.
Not tainted 4.14.112 #2
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.3 D25168 7108 1 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2807 [inline]
__schedule+0x7be/0x1cf0 kernel/sched/core.c:3383
schedule+0x92/0x1c0 kernel/sched/core.c:3427
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3485
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x73c/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
__lo_release drivers/block/loop.c:1644 [inline]
lo_release+0x84/0x1b0 drivers/block/loop.c:1668
__blkdev_put+0x436/0x7f0 fs/block_dev.c:1791
blkdev_put+0x88/0x510 fs/block_dev.c:1856
blkdev_close+0x8b/0xb0 fs/block_dev.c:1863
__fput+0x277/0x7a0 fs/file_table.c:210
____fput+0x16/0x20 fs/file_table.c:244
task_work_run+0x119/0x190 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1da/0x220 arch/x86/entry/common.c:163
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:267 [inline]
do_syscall_64+0x4a9/0x630 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x4129c0
RSP: 002b:00007fff8e6d2e78 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 00000000004129c0
RDX: 0000000000000000 RSI: 0000000000004c01 RDI: 0000000000000003
RBP: 00000000000000b5 R08: 0000000000000000 R09: 000000000000000a
R10: 0000000000000075 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fff8e6d2eb0 R14: 0000000000033bd2 R15: 00007fff8e6d2ec0
INFO: task syz-executor.4:7109 blocked for more than 140 seconds.
Not tainted 4.14.112 #2
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.4 D24320 7109 1 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2807 [inline]
__schedule+0x7be/0x1cf0 kernel/sched/core.c:3383
schedule+0x92/0x1c0 kernel/sched/core.c:3427
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3485
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x73c/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
blkdev_put+0x2b/0x510 fs/block_dev.c:1814
blkdev_close+0x8b/0xb0 fs/block_dev.c:1863
__fput+0x277/0x7a0 fs/file_table.c:210
____fput+0x16/0x20 fs/file_table.c:244
task_work_run+0x119/0x190 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1da/0x220 arch/x86/entry/common.c:163
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:267 [inline]
do_syscall_64+0x4a9/0x630 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x4129c0
RSP: 002b:00007ffe0d2ca848 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 00000000004129c0
RDX: 0000000000000000 RSI: 0000000000004c01 RDI: 0000000000000003
RBP: 00000000000000bc R08: 0000000000000000 R09: 000000000000000a
R10: 0000000000000075 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffe0d2ca880 R14: 0000000000033d0a R15: 00007ffe0d2ca890
INFO: task syz-executor.0:9207 blocked for more than 140 seconds.
Not tainted 4.14.112 #2
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.0 D27296 9207 7102 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2807 [inline]
__schedule+0x7be/0x1cf0 kernel/sched/core.c:3383
schedule+0x92/0x1c0 kernel/sched/core.c:3427
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3485
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x73c/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
blkdev_reread_part+0x1f/0x40 block/ioctl.c:192
loop_reread_partitions+0x7c/0x90 drivers/block/loop.c:615
loop_clr_fd+0x844/0xae0 drivers/block/loop.c:1069
lo_ioctl+0x8d0/0x1c70 drivers/block/loop.c:1415
__blkdev_driver_ioctl block/ioctl.c:297 [inline]
blkdev_ioctl+0x983/0x1880 block/ioctl.c:594
block_ioctl+0xde/0x120 fs/block_dev.c:1881
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x7b9/0x1070 fs/ioctl.c:684
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
do_syscall_64+0x1eb/0x630 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x458a97
RSP: 002b:00007fc1ed9139f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fc1ed9146d4 RCX: 0000000000458a97
RDX: 0000000000000000 RSI: 0000000000004c01 RDI: 0000000000000004
RBP: 0000000000000000 R08: 0000000000000000 R09: 000000000000000c
R10: 0000000000000064 R11: 0000000000000246 R12: 0000000000000003
R13: 0000000000000000 R14: 0000000000000004 R15: 00000000ffffffff
INFO: task blkid:9211 blocked for more than 140 seconds.
Not tainted 4.14.112 #2
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid D28512 9211 7206 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2807 [inline]
__schedule+0x7be/0x1cf0 kernel/sched/core.c:3383
schedule+0x92/0x1c0 kernel/sched/core.c:3427
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3485
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x73c/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
lo_release+0x1e/0x1b0 drivers/block/loop.c:1667
__blkdev_put+0x436/0x7f0 fs/block_dev.c:1791
blkdev_put+0x88/0x510 fs/block_dev.c:1856
blkdev_close+0x8b/0xb0 fs/block_dev.c:1863
__fput+0x277/0x7a0 fs/file_table.c:210
____fput+0x16/0x20 fs/file_table.c:244
task_work_run+0x119/0x190 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1da/0x220 arch/x86/entry/common.c:163
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:267 [inline]
do_syscall_64+0x4a9/0x630 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7f7d37ce82b0
RSP: 002b:00007fff057b98a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007f7d37ce82b0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000001245030
R13: 0000000000000000 R14: 0000000000000003 R15: 0000000000000005
INFO: task blkid:9213 blocked for more than 140 seconds.
Not tainted 4.14.112 #2
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid D28512 9213 7298 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2807 [inline]
__schedule+0x7be/0x1cf0 kernel/sched/core.c:3383
schedule+0x92/0x1c0 kernel/sched/core.c:3427
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3485
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x73c/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
lo_release+0x1e/0x1b0 drivers/block/loop.c:1667
__blkdev_put+0x436/0x7f0 fs/block_dev.c:1791
blkdev_put+0x88/0x510 fs/block_dev.c:1856
blkdev_close+0x8b/0xb0 fs/block_dev.c:1863
__fput+0x277/0x7a0 fs/file_table.c:210
____fput+0x16/0x20 fs/file_table.c:244
task_work_run+0x119/0x190 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1da/0x220 arch/x86/entry/common.c:163
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:267 [inline]
do_syscall_64+0x4a9/0x630 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7f2556d072b0
RSP: 002b:00007ffe77aaa738 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007f2556d072b0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000b95030
R13: 0000000000000000 R14: 0000000000000003 R15: 0000000000000005
INFO: task blkid:9214 blocked for more than 140 seconds.
Not tainted 4.14.112 #2
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid D28512 9214 7720 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2807 [inline]
__schedule+0x7be/0x1cf0 kernel/sched/core.c:3383
schedule+0x92/0x1c0 kernel/sched/core.c:3427
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3485
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x73c/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
lo_release+0x1e/0x1b0 drivers/block/loop.c:1667
__blkdev_put+0x436/0x7f0 fs/block_dev.c:1791
blkdev_put+0x88/0x510 fs/block_dev.c:1856
blkdev_close+0x8b/0xb0 fs/block_dev.c:1863
__fput+0x277/0x7a0 fs/file_table.c:210
____fput+0x16/0x20 fs/file_table.c:244
task_work_run+0x119/0x190 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1da/0x220 arch/x86/entry/common.c:163
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:267 [inline]
do_syscall_64+0x4a9/0x630 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7f55561352b0
RSP: 002b:00007ffc68415e18 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007f55561352b0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000f92030
R13: 0000000000000000 R14: 0000000000000003 R15: 0000000000000005
INFO: task blkid:9220 blocked for more than 140 seconds.
Not tainted 4.14.112 #2
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid D29040 9220 7069 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2807 [inline]
__schedule+0x7be/0x1cf0 kernel/sched/core.c:3383
schedule+0x92/0x1c0 kernel/sched/core.c:3427
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3485
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x73c/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
lo_ioctl+0x87/0x1c70 drivers/block/loop.c:1405
__blkdev_driver_ioctl block/ioctl.c:297 [inline]
blkdev_ioctl+0x983/0x1880 block/ioctl.c:594
block_ioctl+0xde/0x120 fs/block_dev.c:1881
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x7b9/0x1070 fs/ioctl.c:684
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
do_syscall_64+0x1eb/0x630 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7fb8cadd3347
RSP: 002b:00007ffeb9c48db8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000001333030 RCX: 00007fb8cadd3347
RDX: 0000000000000000 RSI: 0000000000005331 RDI: 0000000000000003
RBP: 0000000000000003 R08: 00007fb8cb0835a0 R09: 0000000000000008
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000003 R15: 0000000000000005
INFO: task blkid:9221 blocked for more than 140 seconds.
Not tainted 4.14.112 #2
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid D28568 9221 7068 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2807 [inline]
__schedule+0x7be/0x1cf0 kernel/sched/core.c:3383
schedule+0x92/0x1c0 kernel/sched/core.c:3427
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3485
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x73c/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
lo_ioctl+0x87/0x1c70 drivers/block/loop.c:1405
__blkdev_driver_ioctl block/ioctl.c:297 [inline]
blkdev_ioctl+0x983/0x1880 block/ioctl.c:594
block_ioctl+0xde/0x120 fs/block_dev.c:1881
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x7b9/0x1070 fs/ioctl.c:684
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
do_syscall_64+0x1eb/0x630 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7f3019c6d347
RSP: 002b:00007fff93403228 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000649030 RCX: 00007f3019c6d347
RDX: 0000000000000000 RSI: 0000000000005331 RDI: 0000000000000003
RBP: 0000000000000003 R08: 00007f3019f1d5a0 R09: 0000000000000008
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000200 R14: 0000000000000003 R15: 0000000000000005

Showing all locks held in the system:
1 lock held by khungtaskd/1008:
#0: (tasklist_lock){.+.+}, at: [<ffffffff81485f98>]
debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4544
2 locks held by getty/7060:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff861a9863>]
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff831070a6>]
n_tty_read+0x1e6/0x17b0 drivers/tty/n_tty.c:2156
2 locks held by getty/7061:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff861a9863>]
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff831070a6>]
n_tty_read+0x1e6/0x17b0 drivers/tty/n_tty.c:2156
2 locks held by getty/7062:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff861a9863>]
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff831070a6>]
n_tty_read+0x1e6/0x17b0 drivers/tty/n_tty.c:2156
2 locks held by getty/7063:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff861a9863>]
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff831070a6>]
n_tty_read+0x1e6/0x17b0 drivers/tty/n_tty.c:2156
2 locks held by getty/7064:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff861a9863>]
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff831070a6>]
n_tty_read+0x1e6/0x17b0 drivers/tty/n_tty.c:2156
2 locks held by getty/7065:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff861a9863>]
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff831070a6>]
n_tty_read+0x1e6/0x17b0 drivers/tty/n_tty.c:2156
2 locks held by getty/7066:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff861a9863>]
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff831070a6>]
n_tty_read+0x1e6/0x17b0 drivers/tty/n_tty.c:2156
1 lock held by syz-executor.1/7105:
#0: (&bdev->bd_mutex){+.+.}, at: [<ffffffff819a440b>]
blkdev_put+0x2b/0x510 fs/block_dev.c:1814
1 lock held by syz-executor.2/7107:
#0: (&bdev->bd_mutex){+.+.}, at: [<ffffffff819a440b>]
blkdev_put+0x2b/0x510 fs/block_dev.c:1814
3 locks held by syz-executor.3/7108:
#0: (&bdev->bd_mutex){+.+.}, at: [<ffffffff819a2b76>]
__blkdev_put+0xa6/0x7f0 fs/block_dev.c:1778
#1: (loop_index_mutex){+.+.}, at: [<ffffffff83735b3e>]
lo_release+0x1e/0x1b0 drivers/block/loop.c:1667
#2: (loop_ctl_mutex#2){+.+.}, at: [<ffffffff83735ba4>] __lo_release
drivers/block/loop.c:1644 [inline]
#2: (loop_ctl_mutex#2){+.+.}, at: [<ffffffff83735ba4>]
lo_release+0x84/0x1b0 drivers/block/loop.c:1668
1 lock held by syz-executor.4/7109:
#0: (&bdev->bd_mutex){+.+.}, at: [<ffffffff819a440b>]
blkdev_put+0x2b/0x510 fs/block_dev.c:1814
2 locks held by syz-executor.0/9207:
#0: (loop_ctl_mutex/1){+.+.}, at: [<ffffffff83737817>]
lo_ioctl+0x87/0x1c70 drivers/block/loop.c:1405
#1: (&bdev->bd_mutex){+.+.}, at: [<ffffffff82ca518f>]
blkdev_reread_part+0x1f/0x40 block/ioctl.c:192
2 locks held by blkid/9211:
#0: (&bdev->bd_mutex){+.+.}, at: [<ffffffff819a2b76>]
__blkdev_put+0xa6/0x7f0 fs/block_dev.c:1778
#1: (loop_index_mutex){+.+.}, at: [<ffffffff83735b3e>]
lo_release+0x1e/0x1b0 drivers/block/loop.c:1667
2 locks held by blkid/9213:
#0: (&bdev->bd_mutex){+.+.}, at: [<ffffffff819a2b76>]
__blkdev_put+0xa6/0x7f0 fs/block_dev.c:1778
#1: (loop_index_mutex){+.+.}, at: [<ffffffff83735b3e>]
lo_release+0x1e/0x1b0 drivers/block/loop.c:1667
2 locks held by blkid/9214:
#0: (&bdev->bd_mutex){+.+.}, at: [<ffffffff819a2b76>]
__blkdev_put+0xa6/0x7f0 fs/block_dev.c:1778
#1: (loop_index_mutex){+.+.}, at: [<ffffffff83735b3e>]
lo_release+0x1e/0x1b0 drivers/block/loop.c:1667
1 lock held by blkid/9220:
#0: (loop_ctl_mutex/1){+.+.}, at: [<ffffffff83737817>]
lo_ioctl+0x87/0x1c70 drivers/block/loop.c:1405
1 lock held by blkid/9221:
#0: (loop_ctl_mutex/1){+.+.}, at: [<ffffffff83737817>]
lo_ioctl+0x87/0x1c70 drivers/block/loop.c:1405
1 lock held by blkid/9222:
#0: (&bdev->bd_mutex){+.+.}, at: [<ffffffff819a3405>]
__blkdev_get+0x145/0x1120 fs/block_dev.c:1457
2 locks held by syz-executor.5/9224:
#0: (&bdev->bd_mutex){+.+.}, at: [<ffffffff819a3405>]
__blkdev_get+0x145/0x1120 fs/block_dev.c:1457
#1: (loop_index_mutex){+.+.}, at: [<ffffffff83730f8d>] lo_open+0x1d/0xb0
drivers/block/loop.c:1624

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

NMI backtrace for cpu 0
CPU: 0 PID: 1008 Comm: khungtaskd Not tainted 4.14.112 #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x138/0x19c lib/dump_stack.c:53
nmi_cpu_backtrace.cold+0x57/0x94 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x141/0x189 lib/nmi_backtrace.c:62
arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
trigger_all_cpu_backtrace include/linux/nmi.h:140 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:194 [inline]
watchdog+0x5d8/0xb80 kernel/hung_task.c:250
kthread+0x31c/0x430 kernel/kthread.c:232
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:402
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 7298 Comm: udevd Not tainted 4.14.112 #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
task: ffff88808a398740 task.stack: ffff888065cf8000
RIP: 0033:0x7f3229ad3680
RSP: 002b:00007fff2916be80 EFLAGS: 00000207
RAX: 0000000000000000 RBX: 20c49ba5e353f7cf RCX: 00007f3229ad3678
RDX: 00000000000003e8 RSI: 0000000000000001 RDI: 00007fff2916bf40
RBP: 0000000000000000 R08: 0000000000000008 R09: 0000007437ff41c0
R10: 000da3b1ee800000 R11: 0000000000000246 R12: 0000000001acca10
R13: 00000000000023fd R14: 0000000000000005 R15: 0000000001ac2030
FS: 00007f322a3ca7a0(0000) GS:ffff8880aef00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffc4ec328c8 CR3: 0000000082cc1000 CR4: 00000000001406e0


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[syzbot]

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