INFO: task hung in loop_probe

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 47350a9f ANDROID: x86_64_cuttlefish_defconfig: Enable lz4 ..
git tree: android-4.14
console output: https://syzkaller.appspot.com/x/log.txt?x=14cb2d1e400000
kernel config: https://syzkaller.appspot.com/x/.config?x=10d236078f3378a3
dashboard link: https://syzkaller.appspot.com/bug?extid=13fbe14f8fe5bc45fdc8
compiler: gcc (GCC) 8.0.1 20180413 (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+13fbe1...@syzkaller.appspotmail.com

INFO: task syz-executor0:2040 blocked for more than 140 seconds.
Not tainted 4.14.67+ #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0 D26376 2040 1 0x00000004
Call Trace:
schedule+0x7f/0x1b0 kernel/sched/core.c:3490
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3548
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x521/0x1480 kernel/locking/mutex.c:893
loop_probe+0x71/0x180 drivers/block/loop.c:1931
kobj_lookup+0x230/0x420 drivers/base/map.c:124
get_gendisk+0x32/0x230 block/genhd.c:785
__blkdev_get+0x345/0xe50 fs/block_dev.c:1446
blkdev_get+0x97/0x8c0 fs/block_dev.c:1604
blkdev_open+0x1bd/0x240 fs/block_dev.c:1762
do_dentry_open+0x426/0xda0 fs/open.c:764
vfs_open+0x11c/0x210 fs/open.c:878
do_last fs/namei.c:3408 [inline]
path_openat+0x4eb/0x23a0 fs/namei.c:3550
do_filp_open+0x197/0x270 fs/namei.c:3584
do_sys_open+0x2ef/0x580 fs/open.c:1071
do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x410db0
RSP: 002b:00007ffe290fe338 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000410db0
RDX: 00007ffe290fe37a RSI: 0000000000000002 RDI: 00007ffe290fe370
RBP: 000000000000086f R08: 0000000000000000 R09: 000000000000000a
R10: 0000000000000075 R11: 0000000000000246 R12: 000000000000000d
R13: 000000000005a139 R14: 000000000000021e R15: badc0ffeebadface
INFO: task syz-executor3:2043 blocked for more than 140 seconds.
Not tainted 4.14.67+ #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor3 D27384 2043 1 0x00000004
Call Trace:
schedule+0x7f/0x1b0 kernel/sched/core.c:3490
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3548
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x521/0x1480 kernel/locking/mutex.c:893
lo_open+0x17/0xa0 drivers/block/loop.c:1592
__blkdev_get+0x8e2/0xe50 fs/block_dev.c:1529
blkdev_get+0x97/0x8c0 fs/block_dev.c:1604
blkdev_open+0x1bd/0x240 fs/block_dev.c:1762
do_dentry_open+0x426/0xda0 fs/open.c:764
vfs_open+0x11c/0x210 fs/open.c:878
do_last fs/namei.c:3408 [inline]
path_openat+0x4eb/0x23a0 fs/namei.c:3550
do_filp_open+0x197/0x270 fs/namei.c:3584
do_sys_open+0x2ef/0x580 fs/open.c:1071
do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x410db0
RSP: 002b:00007ffd395aa7f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000410db0
RDX: 00007ffd395aa83a RSI: 0000000000000002 RDI: 00007ffd395aa830
RBP: 000000000000083a R08: 0000000000000000 R09: 000000000000000a
R10: 0000000000000075 R11: 0000000000000246 R12: 0000000000000019
R13: 000000000005a134 R14: 000000000000020b R15: badc0ffeebadface
INFO: task syz-executor7:18945 blocked for more than 140 seconds.
Not tainted 4.14.67+ #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor7 D28104 18945 1 0x00000004
Call Trace:
schedule+0x7f/0x1b0 kernel/sched/core.c:3490
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3548
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x521/0x1480 kernel/locking/mutex.c:893
lo_open+0x17/0xa0 drivers/block/loop.c:1592
__blkdev_get+0x267/0xe50 fs/block_dev.c:1467
blkdev_get+0x97/0x8c0 fs/block_dev.c:1604
blkdev_open+0x1bd/0x240 fs/block_dev.c:1762
do_dentry_open+0x426/0xda0 fs/open.c:764
vfs_open+0x11c/0x210 fs/open.c:878
do_last fs/namei.c:3408 [inline]
path_openat+0x4eb/0x23a0 fs/namei.c:3550
do_filp_open+0x197/0x270 fs/namei.c:3584
do_sys_open+0x2ef/0x580 fs/open.c:1071
do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x410db0
RSP: 002b:00007ffdb3c4d7b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000410db0
RDX: 00007ffdb3c4d7fa RSI: 0000000000000002 RDI: 00007ffdb3c4d7f0
RBP: 00000000000003a7 R08: 0000000000000000 R09: 000000000000000a
R10: 0000000000000075 R11: 0000000000000246 R12: 0000000000000014
R13: 000000000005a11f R14: 00000000000000ce R15: badc0ffeebadface
INFO: task syz-executor1:3323 blocked for more than 140 seconds.
Not tainted 4.14.67+ #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor1 D30216 3323 8865 0x00000004
Call Trace:
schedule+0x7f/0x1b0 kernel/sched/core.c:3490
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3548
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x521/0x1480 kernel/locking/mutex.c:893
loop_control_ioctl+0x71/0x310 drivers/block/loop.c:1951
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x1a0/0x1030 fs/ioctl.c:684
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x7e/0xb0 fs/ioctl.c:692
do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x457099
RSP: 002b:00007f71e96ccc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f71e96cd6d4 RCX: 0000000000457099
RDX: 0000000000000000 RSI: 0000000000004c81 RDI: 0000000000000006
RBP: 00000000009301e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004cf8c8 R14: 00000000004c5b29 R15: 0000000000000002
INFO: task blkid:3160 blocked for more than 140 seconds.
Not tainted 4.14.67+ #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid D27688 3160 6557 0x00000004
Call Trace:
schedule+0x7f/0x1b0 kernel/sched/core.c:3490
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3548
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x521/0x1480 kernel/locking/mutex.c:893
blkdev_put+0x27/0x4d0 fs/block_dev.c:1806
blkdev_close+0x86/0xb0 fs/block_dev.c:1855
__fput+0x25e/0x6f0 fs/file_table.c:210
task_work_run+0x116/0x190 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x12e/0x150 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+0x35d/0x4b0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7f6969ccb2b0
RSP: 002b:00007fffce7e59b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007f6969ccb2b0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000028 R09: 0000000001680000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000064d030
R13: 0000000000000000 R14: 0000000000000003 R15: 0000000000000005
INFO: task blkid:3161 blocked for more than 140 seconds.
Not tainted 4.14.67+ #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid D28376 3161 17629 0x00000004
Call Trace:
schedule+0x7f/0x1b0 kernel/sched/core.c:3490
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3548
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x521/0x1480 kernel/locking/mutex.c:893
lo_release+0x1a/0x190 drivers/block/loop.c:1635
__blkdev_put+0x526/0x6e0 fs/block_dev.c:1783
blkdev_close+0x86/0xb0 fs/block_dev.c:1855
__fput+0x25e/0x6f0 fs/file_table.c:210
task_work_run+0x116/0x190 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x12e/0x150 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+0x35d/0x4b0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7f8a733752b0
RSP: 002b:00007ffc7e0ba728 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007f8a733752b0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000241e030
R13: 0000000000000000 R14: 0000000000000003 R15: 0000000000000005
INFO: task syz-executor2:3178 blocked for more than 140 seconds.
Not tainted 4.14.67+ #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor2 D27992 3178 2042 0x00000004
Call Trace:
schedule+0x7f/0x1b0 kernel/sched/core.c:3490
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3548
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x521/0x1480 kernel/locking/mutex.c:893
blkdev_reread_part+0x18/0x30 block/ioctl.c:192
loop_reread_partitions+0x72/0x80 drivers/block/loop.c:614
loop_set_status+0xa84/0xf40 drivers/block/loop.c:1169
loop_set_status64+0x8d/0xe0 drivers/block/loop.c:1287
lo_ioctl+0x3cd/0x17d0 drivers/block/loop.c:1400
__blkdev_driver_ioctl block/ioctl.c:297 [inline]
blkdev_ioctl+0x57d/0x18c0 block/ioctl.c:594
block_ioctl+0xd9/0x120 fs/block_dev.c:1873
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x1a0/0x1030 fs/ioctl.c:684
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x7e/0xb0 fs/ioctl.c:692
do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x456f07
RSP: 002b:00007f355ce4ea18 EFLAGS: 00000202 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f355ce4f6d4 RCX: 0000000000456f07
RDX: 00007f355ce4eab0 RSI: 0000000000004c04 RDI: 0000000000000005
RBP: 0000000000000001 R08: 0000000000000000 R09: 000000000000000a
R10: 0000000000000075 R11: 0000000000000202 R12: 00007f355ce4f6d4
R13: 0000000000000004 R14: 0000000000000005 R15: 0000000000000001
INFO: task syz-executor5:3223 blocked for more than 140 seconds.
Not tainted 4.14.67+ #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor5 D29848 3223 17032 0x00000004
Call Trace:
schedule+0x7f/0x1b0 kernel/sched/core.c:3490
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3548
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x521/0x1480 kernel/locking/mutex.c:893
loop_control_ioctl+0x180/0x310 drivers/block/loop.c:1965
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x1a0/0x1030 fs/ioctl.c:684
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x7e/0xb0 fs/ioctl.c:692
do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x457099
RSP: 002b:00007f1e6d374c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f1e6d3756d4 RCX: 0000000000457099
RDX: 0000000000000002 RSI: 0000000000004c81 RDI: 0000000000000006
RBP: 00000000009301e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004cf8c8 R14: 00000000004c5b29 R15: 0000000000000002
INFO: task syz-executor6:3180 blocked for more than 140 seconds.
Not tainted 4.14.67+ #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor6 D28168 3180 2041 0x00000004
Call Trace:
schedule+0x7f/0x1b0 kernel/sched/core.c:3490
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3548
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x521/0x1480 kernel/locking/mutex.c:893
blkdev_reread_part+0x18/0x30 block/ioctl.c:192
loop_reread_partitions+0x72/0x80 drivers/block/loop.c:614
loop_set_status+0xa84/0xf40 drivers/block/loop.c:1169
loop_set_status64+0x8d/0xe0 drivers/block/loop.c:1287
lo_ioctl+0x3cd/0x17d0 drivers/block/loop.c:1400
__blkdev_driver_ioctl block/ioctl.c:297 [inline]
blkdev_ioctl+0x57d/0x18c0 block/ioctl.c:594
block_ioctl+0xd9/0x120 fs/block_dev.c:1873
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x1a0/0x1030 fs/ioctl.c:684
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x7e/0xb0 fs/ioctl.c:692
do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x456f07
RSP: 002b:00007f85bcd69a18 EFLAGS: 00000202 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f85bcd6a6d4 RCX: 0000000000456f07
RDX: 00007f85bcd69ab0 RSI: 0000000000004c04 RDI: 0000000000000005
RBP: 0000000000000001 R08: 0000000000000000 R09: 000000000000000a
R10: 0000000000000075 R11: 0000000000000202 R12: 00007f85bcd6a6d4
R13: 0000000000000004 R14: 0000000000000005 R15: 0000000000000001
INFO: task blkid:3221 blocked for more than 140 seconds.
Not tainted 4.14.67+ #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid D28728 3221 6450 0x00000004
Call Trace:
schedule+0x7f/0x1b0 kernel/sched/core.c:3490
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3548
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x521/0x1480 kernel/locking/mutex.c:893
lo_open+0x17/0xa0 drivers/block/loop.c:1592
__blkdev_get+0x8e2/0xe50 fs/block_dev.c:1529
blkdev_get+0x97/0x8c0 fs/block_dev.c:1604
blkdev_open+0x1bd/0x240 fs/block_dev.c:1762
do_dentry_open+0x426/0xda0 fs/open.c:764
vfs_open+0x11c/0x210 fs/open.c:878
do_last fs/namei.c:3408 [inline]
path_openat+0x4eb/0x23a0 fs/namei.c:3550
do_filp_open+0x197/0x270 fs/namei.c:3584
do_sys_open+0x2ef/0x580 fs/open.c:1071
do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7fe8f22a5120
RSP: 002b:00007ffc2e749928 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fe8f22a5120
RDX: 00007ffc2e74af41 RSI: 0000000000000000 RDI: 00007ffc2e74af41
RBP: 0000000000000000 R08: 0000000000000078 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000169a030
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000005

Showing all locks held in the system:
1 lock held by khungtaskd/23:
#0: (tasklist_lock){.+.+}, at: [<ffffffff85801847>]
debug_show_all_locks+0x74/0x20f kernel/locking/lockdep.c:4541
1 lock held by rsyslogd/1854:
#0: (&f->f_pos_lock){+.+.}, at: [<ffffffff85bbcab2>]
__fdget_pos+0xa2/0xc0 fs/file.c:768
2 locks held by getty/1950:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff8631c500>]
tty_ldisc_ref_wait+0x20/0x80 drivers/tty/tty_ldisc.c:275
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff86317a7f>]
n_tty_read+0x1ff/0x15e0 drivers/tty/n_tty.c:2142
1 lock held by syz-executor0/2040:
#0: (loop_index_mutex){+.+.}, at: [<ffffffff863ce4c1>]
loop_probe+0x71/0x180 drivers/block/loop.c:1931
2 locks held by syz-executor3/2043:
#0: (&bdev->bd_mutex){+.+.}, at: [<ffffffff85c188c3>]
__blkdev_get+0xf3/0xe50 fs/block_dev.c:1452
#1: (loop_index_mutex){+.+.}, at: [<ffffffff863c7107>] lo_open+0x17/0xa0
drivers/block/loop.c:1592
2 locks held by syz-executor7/18945:
#0: (&bdev->bd_mutex){+.+.}, at: [<ffffffff85c188c3>]
__blkdev_get+0xf3/0xe50 fs/block_dev.c:1452
#1: (loop_index_mutex){+.+.}, at: [<ffffffff863c7107>] lo_open+0x17/0xa0
drivers/block/loop.c:1592
1 lock held by syz-executor1/3323:
#0: (loop_index_mutex){+.+.}, at: [<ffffffff863ce641>]
loop_control_ioctl+0x71/0x310 drivers/block/loop.c:1951
1 lock held by blkid/3160:
#0: (&bdev->bd_mutex){+.+.}, at: [<ffffffff85c19647>]
blkdev_put+0x27/0x4d0 fs/block_dev.c:1806
2 locks held by blkid/3161:
#0: (&bdev->bd_mutex){+.+.}, at: [<ffffffff85c181a1>]
__blkdev_put+0xb1/0x6e0 fs/block_dev.c:1770
#1: (loop_index_mutex){+.+.}, at: [<ffffffff863cd16a>]
lo_release+0x1a/0x190 drivers/block/loop.c:1635
2 locks held by syz-executor2/3178:
#0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<ffffffff863cb8d5>]
lo_ioctl+0x85/0x17d0 drivers/block/loop.c:1373
#1: (&bdev->bd_mutex){+.+.}, at: [<ffffffff860fd838>]
blkdev_reread_part+0x18/0x30 block/ioctl.c:192
2 locks held by syz-executor5/3223:
#0: (loop_index_mutex){+.+.}, at: [<ffffffff863ce641>]
loop_control_ioctl+0x71/0x310 drivers/block/loop.c:1951
#1: (&lo->lo_ctl_mutex#2){+.+.}, at: [<ffffffff863ce750>]
loop_control_ioctl+0x180/0x310 drivers/block/loop.c:1965
2 locks held by syz-executor6/3180:
#0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<ffffffff863cb8d5>]
lo_ioctl+0x85/0x17d0 drivers/block/loop.c:1373
#1: (&bdev->bd_mutex){+.+.}, at: [<ffffffff860fd838>]
blkdev_reread_part+0x18/0x30 block/ioctl.c:192
2 locks held by blkid/3221:
#0: (&bdev->bd_mutex){+.+.}, at: [<ffffffff85c188c3>]
__blkdev_get+0xf3/0xe50 fs/block_dev.c:1452
#1: (loop_index_mutex){+.+.}, at: [<ffffffff863c7107>] lo_open+0x17/0xa0
drivers/block/loop.c:1592

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

NMI backtrace for cpu 0
CPU: 0 PID: 23 Comm: khungtaskd Not tainted 4.14.67+ #1
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0xb9/0x11b lib/dump_stack.c:53
nmi_cpu_backtrace.cold.0+0x18/0x8e lib/nmi_backtrace.c:103
nmi_trigger_cpumask_backtrace+0x121/0x146 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:138 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:196 [inline]
watchdog+0x574/0xa70 kernel/hung_task.c:252
kthread+0x348/0x420 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 skipped: idling at pc 0xffffffff86e40572


---
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[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 71fce1ed UPSTREAM: tracing: always define trace_{irq,preem..
git tree: android-4.9
console output: https://syzkaller.appspot.com/x/log.txt?x=118b5247800000
kernel config: https://syzkaller.appspot.com/x/.config?x=a54f56879744de40
dashboard link: https://syzkaller.appspot.com/bug?extid=5a733e158a1b007f0d62

compiler: gcc (GCC) 8.0.1 20180413 (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+5a733e...@syzkaller.appspotmail.com

IPVS: Creating netns size=2536 id=20
syz-executor3 uses obsolete (PF_INET,SOCK_PACKET)
INFO: task syz-executor0:3777 blocked for more than 120 seconds.
Not tainted 4.9.96-g71fce1e #10

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

syz-executor0 D26104 3777 3772 0x00000000
ffff8801d9510000 0000000000000000 ffff8801d951af40 ffff8801d9a6b000
ffff8801db321b98 ffff8801bd6874e8 ffffffff839e240d ffff8801d95108c8
ffffed003b2a2118 ffff8801d9510000 00fffc0000000000 ffff8801db322468
Call Trace:
[<ffffffff839e3a0f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
[<ffffffff839e4393>] schedule_preempt_disabled+0x13/0x20
kernel/sched/core.c:3590
[<ffffffff839e8816>] __mutex_lock_common kernel/locking/mutex.c:582
[inline]
[<ffffffff839e8816>] mutex_lock_nested+0x326/0x870
kernel/locking/mutex.c:621
[<ffffffff825c9874>] loop_probe+0x74/0x180 drivers/block/loop.c:1886
[<ffffffff8256ec03>] kobj_lookup+0x223/0x410 drivers/base/map.c:124
[<ffffffff81e57a19>] get_gendisk+0x39/0x2d0 block/genhd.c:716
[<ffffffff8162ec81>] __blkdev_get+0x351/0xd60 fs/block_dev.c:1262
[<ffffffff81631f2a>] blkdev_get+0x2da/0x920 fs/block_dev.c:1416
[<ffffffff81632785>] blkdev_open+0x1a5/0x250 fs/block_dev.c:1571
[<ffffffff81567583>] do_dentry_open+0x703/0xc80 fs/open.c:766
[<ffffffff8156ad6c>] vfs_open+0x11c/0x210 fs/open.c:879
[<ffffffff815a1ea8>] do_last fs/namei.c:3410 [inline]
[<ffffffff815a1ea8>] path_openat+0x758/0x3590 fs/namei.c:3534
[<ffffffff815a8fa7>] do_filp_open+0x197/0x270 fs/namei.c:3568
[<ffffffff8156b77d>] do_sys_open+0x30d/0x5c0 fs/open.c:1072
[<ffffffff8156ba5d>] SYSC_open fs/open.c:1090 [inline]
[<ffffffff8156ba5d>] SyS_open+0x2d/0x40 fs/open.c:1085
[<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
[<ffffffff839f3313>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:

2 locks held by khungtaskd/518:
#0: (rcu_read_lock){......}, at: [<ffffffff813646ec>]
check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
#0: (rcu_read_lock){......}, at: [<ffffffff813646ec>]
watchdog+0x11c/0xa20 kernel/hung_task.c:239
#1: (tasklist_lock){.+.+..}, at: [<ffffffff81423ce0>]
debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
1 lock held by rsyslogd/3584:
#0: (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d579c>]
__fdget_pos+0xac/0xd0 fs/file.c:781
2 locks held by getty/3680:
#0: (&tty->ldisc_sem){++++++}, at: [<ffffffff839f14b2>]
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
#1: (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211c792>]
n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133
1 lock held by syz-executor0/3777:
#0: (loop_index_mutex){+.+.+.}, at: [<ffffffff825c9874>]
loop_probe+0x74/0x180 drivers/block/loop.c:1886
2 locks held by syz-executor4/3786:
#0: (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162ea3c>]
__blkdev_get+0x10c/0xd60 fs/block_dev.c:1268
#1: (loop_index_mutex){+.+.+.}, at: [<ffffffff825c203b>]
lo_open+0x1b/0xa0 drivers/block/loop.c:1555
2 locks held by syz-executor6/3792:
#0: (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162ea3c>]
__blkdev_get+0x10c/0xd60 fs/block_dev.c:1268
#1: (loop_index_mutex){+.+.+.}, at: [<ffffffff825c203b>]
lo_open+0x1b/0xa0 drivers/block/loop.c:1555
1 lock held by syz-executor5/8273:
#0: (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162ea3c>]
__blkdev_get+0x10c/0xd60 fs/block_dev.c:1268
2 locks held by syz-executor2/9497:
#0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c6f9b>]
lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
#1: (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff81e531ee>]
blkdev_reread_part+0x1e/0x40 block/ioctl.c:189
2 locks held by syz-executor7/9496:
#0: (loop_index_mutex){+.+.+.}, at: [<ffffffff825c957a>]
loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1906
#1: (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<ffffffff825c9686>]
loop_control_ioctl+0x186/0x300 drivers/block/loop.c:1920
1 lock held by syz-executor7/9556:
#0: (loop_index_mutex){+.+.+.}, at: [<ffffffff825c957a>]
loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1906
1 lock held by syz-executor7/9557:
#0: (loop_index_mutex){+.+.+.}, at: [<ffffffff825c957a>]
loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1906
1 lock held by syz-executor7/9558:
#0: (loop_index_mutex){+.+.+.}, at: [<ffffffff825c957a>]
loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1906
1 lock held by syz-executor7/9559:
#0: (loop_index_mutex){+.+.+.}, at: [<ffffffff825c957a>]
loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1906
1 lock held by syz-executor7/9560:
#0: (loop_index_mutex){+.+.+.}, at: [<ffffffff825c957a>]
loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1906
1 lock held by syz-executor7/9562:
#0: (loop_index_mutex){+.+.+.}, at: [<ffffffff825c957a>]
loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1906
1 lock held by syz-executor7/9564:
#0: (loop_index_mutex){+.+.+.}, at: [<ffffffff825c957a>]
loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1906
2 locks held by blkid/9529:
#0: (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162ea3c>]
__blkdev_get+0x10c/0xd60 fs/block_dev.c:1268
#1: (loop_index_mutex){+.+.+.}, at: [<ffffffff825c203b>]
lo_open+0x1b/0xa0 drivers/block/loop.c:1555
1 lock held by syz-executor3/9548:
#0: (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162ea3c>]
__blkdev_get+0x10c/0xd60 fs/block_dev.c:1268
1 lock held by syz-executor3/9566:
#0: (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162ea3c>]
__blkdev_get+0x10c/0xd60 fs/block_dev.c:1268
2 locks held by blkid/9540:
#0: (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162ea3c>]
__blkdev_get+0x10c/0xd60 fs/block_dev.c:1268
#1: (loop_index_mutex){+.+.+.}, at: [<ffffffff825c203b>]
lo_open+0x1b/0xa0 drivers/block/loop.c:1555
2 locks held by blkid/9541:
#0: (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162ea3c>]
__blkdev_get+0x10c/0xd60 fs/block_dev.c:1268
#1: (loop_index_mutex){+.+.+.}, at: [<ffffffff825c203b>]
lo_open+0x1b/0xa0 drivers/block/loop.c:1555

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

NMI backtrace for cpu 0

CPU: 0 PID: 518 Comm: khungtaskd Not tainted 4.9.96-g71fce1e #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
ffff8801d85efd08 ffffffff81eb0b69 0000000000000000 0000000000000000
0000000000000000 0000000000000001 ffffffff810b7d60 ffff8801d85efd40
ffffffff81ebbe97 0000000000000000 0000000000000000 0000000000000003
Call Trace:
[<ffffffff81eb0b69>] __dump_stack lib/dump_stack.c:15 [inline]
[<ffffffff81eb0b69>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
[<ffffffff81ebbe97>] nmi_cpu_backtrace.cold.2+0x48/0x87
lib/nmi_backtrace.c:99
[<ffffffff81ebbe2a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f
lib/nmi_backtrace.c:60
[<ffffffff810b7e64>] arch_trigger_cpumask_backtrace+0x14/0x20
arch/x86/kernel/apic/hw_nmi.c:37
[<ffffffff81364c84>] trigger_all_cpu_backtrace include/linux/nmi.h:58
[inline]
[<ffffffff81364c84>] check_hung_task kernel/hung_task.c:125 [inline]
[<ffffffff81364c84>] check_hung_uninterruptible_tasks
kernel/hung_task.c:182 [inline]
[<ffffffff81364c84>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
[<ffffffff8119ad5d>] kthread+0x26d/0x300 kernel/kthread.c:211
[<ffffffff839f34dc>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373

Sending NMI from CPU 0 to CPUs 1:

NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff839f1f16

[syzbot]

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

[syzbot]