INFO: task hung in lo_release

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: b11964ad ANDROID: cuttlefish: enable CONFIG_INET_UDP_DIAG=y
git tree: android-4.14
console output: https://syzkaller.appspot.com/x/log.txt?x=120f1313200000
kernel config: https://syzkaller.appspot.com/x/.config?x=322dd7397c84f390
dashboard link: https://syzkaller.appspot.com/bug?extid=e79dcc3616b4360760a0
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=121304cf200000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e79dcc...@syzkaller.appspotmail.com

random: cc1: uninitialized urandom read (8 bytes read)
audit: type=1400 audit(1552198896.753:10): avc: denied { map } for
pid=1954 comm="syz-execprog" path="/root/syzkaller-shm123699983" dev="sda1"
ino=16482 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
tcontext=unconfined_u:object_r:file_t:s0 tclass=file permissive=1
INFO: task blkid:2117 blocked for more than 140 seconds.
Not tainted 4.14.105+ #29
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid D28664 2117 309 0x00000004
Call Trace:
schedule+0x92/0x1c0 kernel/sched/core.c:3492
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3550
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x559/0x1430 kernel/locking/mutex.c:893
__lo_release drivers/block/loop.c:1644 [inline]
lo_release+0x78/0x190 drivers/block/loop.c:1668
__blkdev_put+0x518/0x6d0 fs/block_dev.c:1791
blkdev_close+0x86/0xb0 fs/block_dev.c:1863
__fput+0x25e/0x700 fs/file_table.c:210
task_work_run+0x118/0x190 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x13b/0x160 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+0x372/0x4b0 arch/x86/entry/common.c:294
INFO: task syz-executor.0:2118 blocked for more than 140 seconds.
Not tainted 4.14.105+ #29
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.0 D27272 2118 1968 0x00000004
Call Trace:
schedule+0x92/0x1c0 kernel/sched/core.c:3492
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3550
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x559/0x1430 kernel/locking/mutex.c:893
blkdev_reread_part+0x1b/0x40 block/ioctl.c:192
loop_reread_partitions+0x72/0x80 drivers/block/loop.c:615
loop_set_status+0xbff/0x11f0 drivers/block/loop.c:1184
INFO: task blkid:2120 blocked for more than 140 seconds.
Not tainted 4.14.105+ #29
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid D28936 2120 310 0x00000004
Call Trace:
schedule+0x92/0x1c0 kernel/sched/core.c:3492
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3550
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x559/0x1430 kernel/locking/mutex.c:893
lo_open+0x19/0xb0 drivers/block/loop.c:1624
__blkdev_get+0x963/0xf90 fs/block_dev.c:1537
blkdev_get+0x97/0x8b0 fs/block_dev.c:1612
blkdev_open+0x1cc/0x250 fs/block_dev.c:1770
do_dentry_open+0x41b/0xd60 fs/open.c:764
vfs_open+0x105/0x230 fs/open.c:878
do_last fs/namei.c:3455 [inline]
path_openat+0xb6b/0x2b70 fs/namei.c:3597
do_filp_open+0x1a1/0x280 fs/namei.c:3631
do_sys_open+0x2ca/0x590 fs/open.c:1071
do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289

Showing all locks held in the system:
1 lock held by khungtaskd/23:
#0: (tasklist_lock){.+.+}, at: [<ffffffffb7000e0c>]
debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4541
2 locks held by getty/1762:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffffb7b38782>]
tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:275
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffffb7b33ba7>]
n_tty_read+0x1f7/0x1700 drivers/tty/n_tty.c:2156
3 locks held by blkid/2117:
#0: (&bdev->bd_mutex){+.+.}, at: [<ffffffffb74167d1>]
__blkdev_put+0xb1/0x6d0 fs/block_dev.c:1778
#1: (loop_index_mutex){+.+.}, at: [<ffffffffb7bea1d9>]
lo_release+0x19/0x190 drivers/block/loop.c:1667
#2: (loop_ctl_mutex#2){+.+.}, at: [<ffffffffb7bea238>] __lo_release
drivers/block/loop.c:1644 [inline]
#2: (loop_ctl_mutex#2){+.+.}, at: [<ffffffffb7bea238>]
lo_release+0x78/0x190 drivers/block/loop.c:1668
2 locks held by syz-executor.0/2118:
#0: (loop_ctl_mutex/1){+.+.}, at: [<ffffffffb7be87a3>]
lo_ioctl+0x83/0x1970 drivers/block/loop.c:1405
#1: (&bdev->bd_mutex){+.+.}, at: [<ffffffffb791b5ab>]
blkdev_reread_part+0x1b/0x40 block/ioctl.c:192
2 locks held by blkid/2120:
#0: (&bdev->bd_mutex){+.+.}, at: [<ffffffffb7416ee3>]
__blkdev_get+0xf3/0xf90 fs/block_dev.c:1457
#1: (loop_index_mutex){+.+.}, at: [<ffffffffb7be3b99>] lo_open+0x19/0xb0
drivers/block/loop.c:1624

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

NMI backtrace for cpu 1
CPU: 1 PID: 23 Comm: khungtaskd Not tainted 4.14.105+ #29
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0xb9/0x10e lib/dump_stack.c:53
nmi_cpu_backtrace.cold+0x47/0x86 lib/nmi_backtrace.c:101
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at pc 0xffffffffb86430b2


---
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 can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 62872f95 Merge 4.4.174 into android-4.4
git tree: android-4.4
console output: https://syzkaller.appspot.com/x/log.txt?x=10797723200000
kernel config: https://syzkaller.appspot.com/x/.config?x=47bc4dd423780c4a
dashboard link: https://syzkaller.appspot.com/bug?extid=080cc4a0776f78b26616

compiler: gcc (GCC) 9.0.0 20181231 (experimental)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10a98c83200000

IMPORTANT: if you fix the bug, please add the following tag to the commit:

Reported-by: syzbot+080cc4...@syzkaller.appspotmail.com

INFO: task blkid:2613 blocked for more than 140 seconds.
Not tainted 4.4.174+ #4

"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

blkid D ffff8800b1dd7af8 29008 2613 589 0x00000004
ffff8800b1dd7af8 ffff8800b25997c0 62c6ad62307c3c56 ffff8800b25997c0
0000000000000002 ffff8800b259a000 ffff8801db71f180 ffff8801db71f1a8
ffff8801db71e898 ffff8800b259af80 ffff8800b25997c0 ffffed00163ba001
Call Trace:
[<ffffffff82709b79>] schedule+0x99/0x1d0 kernel/sched/core.c:3355
[<ffffffff8270a333>] schedule_preempt_disabled+0x13/0x20
kernel/sched/core.c:3388
[<ffffffff8270c492>] __mutex_lock_common kernel/locking/mutex.c:582
[inline]
[<ffffffff8270c492>] mutex_lock_nested+0x3c2/0xb80
kernel/locking/mutex.c:621
[<ffffffff81d48124>] __lo_release drivers/block/loop.c:1653 [inline]
[<ffffffff81d48124>] lo_release+0x84/0x1b0 drivers/block/loop.c:1676
[<ffffffff8154e4e1>] __blkdev_put+0x461/0x840 fs/block_dev.c:1535
[<ffffffff8154f738>] blkdev_put+0x88/0x560 fs/block_dev.c:1600
[<ffffffff8154fc9b>] blkdev_close+0x8b/0xb0 fs/block_dev.c:1607
[<ffffffff8149c8c6>] __fput+0x246/0x710 fs/file_table.c:208
[<ffffffff8149ce16>] ____fput+0x16/0x20 fs/file_table.c:244
[<ffffffff8112f352>] task_work_run+0x202/0x2b0 kernel/task_work.c:115
[<ffffffff81003dca>] tracehook_notify_resume include/linux/tracehook.h:191
[inline]
[<ffffffff81003dca>] exit_to_usermode_loop+0x14a/0x170
arch/x86/entry/common.c:188
[<ffffffff8100569b>] prepare_exit_to_usermode arch/x86/entry/common.c:221
[inline]
[<ffffffff8100569b>] syscall_return_slowpath+0x25b/0x2e0
arch/x86/entry/common.c:286
[<ffffffff82718ce1>] int_ret_from_sys_call+0x25/0xa3
3 locks held by blkid/2613:
#0: (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8154e13b>]
__blkdev_put+0xbb/0x840 fs/block_dev.c:1516
#1: (loop_index_mutex){+.+.+.}, at: [<ffffffff81d480be>]
lo_release+0x1e/0x1b0 drivers/block/loop.c:1675
#2: (loop_ctl_mutex#2){+.+.+.}, at: [<ffffffff81d48124>] __lo_release
drivers/block/loop.c:1653 [inline]
#2: (loop_ctl_mutex#2){+.+.+.}, at: [<ffffffff81d48124>]
lo_release+0x84/0x1b0 drivers/block/loop.c:1676
Sending NMI to all CPUs:

NMI backtrace for cpu 0

CPU: 0 PID: 20 Comm: khungtaskd Not tainted 4.4.174+ #4
task: ffff8801da6f4740 task.stack: ffff8800001d0000
RIP: 0010:[<ffffffff8109b617>] [<ffffffff8109b617>] _flat_send_IPI_mask
arch/x86/kernel/apic/apic_flat_64.c:62 [inline]
RIP: 0010:[<ffffffff8109b617>] [<ffffffff8109b617>]
flat_send_IPI_mask+0xf7/0x1b0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8800001d7c88 EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fc300
RBP: ffff8800001d7cb8 R08: 0000000000000018 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000003000000 R14: ffffffff82e5f2e0 R15: 0000000000000002
FS: 0000000000000000(0000) GS:ffff8801db600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2793805000 CR3: 00000000b4a58000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
0000000000000001 ffffffff82e5f2e0 ffffffff831a6ac0 fffffbfff0634c34
000000000001b6c0 0000000000000008 ffff8800001d7cd8 ffffffff81092bee
0000000000000008 ffffffff82924260 ffff8800001d7d30 ffffffff81ab8252
Call Trace:
[<ffffffff81092bee>] nmi_raise_cpu_backtrace+0x5e/0x80
arch/x86/kernel/apic/hw_nmi.c:33
[<ffffffff81ab8252>] nmi_trigger_all_cpu_backtrace.cold+0xa1/0xae
lib/nmi_backtrace.c:85
[<ffffffff81092ca4>] arch_trigger_all_cpu_backtrace+0x14/0x20
arch/x86/kernel/apic/hw_nmi.c:38
[<ffffffff813b4762>] trigger_all_cpu_backtrace include/linux/nmi.h:44
[inline]
[<ffffffff813b4762>] check_hung_task kernel/hung_task.c:125 [inline]
[<ffffffff813b4762>] check_hung_uninterruptible_tasks
kernel/hung_task.c:182 [inline]
[<ffffffff813b4762>] watchdog.cold+0xd3/0xee kernel/hung_task.c:238
[<ffffffff811342c3>] kthread+0x273/0x310 kernel/kthread.c:211
[<ffffffff82718fc5>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:537
Code: 00 c3 5f ff 80 e6 10 75 e1 41 c1 e5 18 44 89 2c 25 10 c3 5f ff 44 89
fa 09 da 80 cf 04 41 83 ff 02 0f 44 d3 89 14 25 00 c3 5f ff <41> f7 c4 00
02 00 00 75 1e 4c 89 e7 57 9d 0f 1f 44 00 00 e8 f1

NMI backtrace for cpu 1

CPU: 1 PID: 1927 Comm: rsyslogd Not tainted 4.4.174+ #4
task: ffff8801d6d55f00 task.stack: ffff8801d6428000
RIP: 0033:[<00007f1cec2c1004>] [<00007f1cec2c1004>] 0x7f1cec2c1004
RSP: 002b:00007f1ce9f68cf0 EFLAGS: 00000206
RAX: 0000000002469480 RBX: 0000000002469588 RCX: 0000000002469470
RDX: 000000000241de10 RSI: 0000000000000000 RDI: 00007f1ce9f68d00
RBP: 0000000002469580 R08: 00007f1cec5ab0a8 R09: 00007f1cec35d100
R10: 0fffffffffffffff R11: 0000000000000000 R12: 0000000000000000
R13: 00007f1ceb79e5a3 R14: 0000000000000574 R15: 00007f1ceb79d5e4
FS: 00007f1ce9f69700(0000) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f355c43da30 CR3: 00000001d875f000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: da9fb784 Merge 4.9.83 into android-4.9
git tree: android-4.9
console output: https://syzkaller.appspot.com/x/log.txt?x=173dc0a3800000
kernel config: https://syzkaller.appspot.com/x/.config?x=287729e29196ff1
dashboard link: https://syzkaller.appspot.com/bug?extid=357e1f2af559567b7333
compiler: gcc (GCC) 7.1.1 20170620

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+357e1f...@syzkaller.appspotmail.com

INFO: task blkid:20189 blocked for more than 120 seconds.
Not tainted 4.9.83-gda9fb78 #40

"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

blkid D28272 20189 2224 0x00000006
ffff8801b7f78000 ffff8801c38eb480 ffff8801c637ea00 ffff8801c2eb6000
ffff8801db221b98 ffff8801b7fc76f8 ffffffff838a3e1b 0000000000000001
0000000000000007 00ff8801b7f78000 ffff8801db222468 ffff8801db222490
Call Trace:
[<ffffffff838a53bf>] schedule+0x7f/0x1b0 kernel/sched/core.c:3550
[<ffffffff838a5d43>] schedule_preempt_disabled+0x13/0x20
kernel/sched/core.c:3583
[<ffffffff838ab352>] __mutex_lock_common kernel/locking/mutex.c:582
[inline]
[<ffffffff838ab352>] mutex_lock_nested+0x312/0x870
kernel/locking/mutex.c:621
[<ffffffff824b9b5f>] lo_release+0x1f/0x160 drivers/block/loop.c:1590
[<ffffffff8162e317>] __blkdev_put+0x5f7/0x7e0 fs/block_dev.c:1598
[<ffffffff8162f2d5>] blkdev_put+0x85/0x550 fs/block_dev.c:1663
[<ffffffff8162f82b>] blkdev_close+0x8b/0xb0 fs/block_dev.c:1670
[<ffffffff8157580c>] __fput+0x28c/0x6e0 fs/file_table.c:208
[<ffffffff81575ce5>] ____fput+0x15/0x20 fs/file_table.c:244
[<ffffffff81195855>] task_work_run+0x115/0x190 kernel/task_work.c:116
[<ffffffff8113c2c7>] exit_task_work include/linux/task_work.h:21 [inline]
[<ffffffff8113c2c7>] do_exit+0x7e7/0x2a40 kernel/exit.c:833
[<ffffffff811429d8>] do_group_exit+0x108/0x320 kernel/exit.c:937
[<ffffffff81165854>] get_signal+0x4d4/0x14e0 kernel/signal.c:2317
[<ffffffff81052c87>] do_signal+0x87/0x19f0 arch/x86/kernel/signal.c:807
[<ffffffff81003a31>] exit_to_usermode_loop+0xe1/0x120
arch/x86/entry/common.c:157
[<ffffffff810066cf>] prepare_exit_to_usermode arch/x86/entry/common.c:191
[inline]
[<ffffffff810066cf>] syscall_return_slowpath arch/x86/entry/common.c:260
[inline]
[<ffffffff810066cf>] do_syscall_64+0x36f/0x490 arch/x86/entry/common.c:287
[<ffffffff838b4e7d>] entry_SYSCALL_64_after_swapgs+0x47/0xc5

Showing all locks held in the system:

2 locks held by khungtaskd/514:
#0: (rcu_read_lock){......}, at: [<ffffffff81373095>]
check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
#0: (rcu_read_lock){......}, at: [<ffffffff81373095>]
watchdog+0x125/0xa70 kernel/hung_task.c:239
#1: (tasklist_lock){.+.?..}, at: [<ffffffff81238190>]
debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336
2 locks held by getty/3664:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff838b3092>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff8200a5a4>]
n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
2 locks held by blkid/20189:
#0: (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162dddc>]
__blkdev_put+0xbc/0x7e0 fs/block_dev.c:1579
#1: (loop_index_mutex){+.+.+.}, at: [<ffffffff824b9b5f>]
lo_release+0x1f/0x160 drivers/block/loop.c:1590
1 lock held by syz-executor2/23126:
#0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff824b727f>]
lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337
2 locks held by syz-executor4/23137:
#0: (loop_index_mutex){+.+.+.}, at: [<ffffffff824b973a>]
loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1899
#1: (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<ffffffff824b9836>]
loop_control_ioctl+0x176/0x300 drivers/block/loop.c:1913

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

NMI backtrace for cpu 0

CPU: 0 PID: 514 Comm: khungtaskd Not tainted 4.9.83-gda9fb78 #40
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
ffff8801d86afd00 ffffffff81d95149 0000000000000000 0000000000000000
0000000000000000 0000000000000001 ffffffff810bb190 ffff8801d86afd38
ffffffff81da026d 0000000000000000 0000000000000000 ffff8801b7f78418
Call Trace:
[<ffffffff81d95149>] __dump_stack lib/dump_stack.c:15 [inline]
[<ffffffff81d95149>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
[<ffffffff81da026d>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
[<ffffffff81da03a7>] nmi_trigger_cpumask_backtrace+0x117/0x190
lib/nmi_backtrace.c:60
[<ffffffff810bb284>] arch_trigger_cpumask_backtrace+0x14/0x20
arch/x86/kernel/apic/hw_nmi.c:37
[<ffffffff81373660>] trigger_all_cpu_backtrace include/linux/nmi.h:58
[inline]
[<ffffffff81373660>] check_hung_task kernel/hung_task.c:125 [inline]
[<ffffffff81373660>] check_hung_uninterruptible_tasks
kernel/hung_task.c:182 [inline]
[<ffffffff81373660>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
[<ffffffff8119a7bd>] kthread+0x26d/0x300 kernel/kthread.c:211
[<ffffffff838b500c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:361
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff838b3b06

[syzbot]

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