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SubjectINFO: task hung in __blkdev_get (2)
From
Hello,

syzbot found the following crash on:

HEAD commit: b50694381cfc Merge branch 'stable/for-linus-4.17' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=166708d7800000
kernel config: https://syzkaller.appspot.com/x/.config?x=982e2df1b9e60b02
dashboard link: https://syzkaller.appspot.com/bug?extid=2a732b5a87000875c1f3
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+2a732b5a87000875c1f3@syzkaller.appspotmail.com

binder: 17633:17652 ioctl c0306201 20007000 returned -22
INFO: task syz-executor0:17586 blocked for more than 120 seconds.
Not tainted 4.17.0-rc6+ #66
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0 D22720 17586 16831 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2859 [inline]
__schedule+0x801/0x1e30 kernel/sched/core.c:3501
schedule+0xef/0x430 kernel/sched/core.c:3545
schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:3603
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0xe38/0x17f0 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
__blkdev_get+0x193/0x13a0 fs/block_dev.c:1460
blkdev_get+0xb9/0xb30 fs/block_dev.c:1611
blkdev_get_by_dev+0x3f/0x80 fs/block_dev.c:1733
journal_init_dev fs/reiserfs/journal.c:2625 [inline]
journal_init+0xcad/0x6a20 fs/reiserfs/journal.c:2772
reiserfs_fill_super+0xd59/0x3900 fs/reiserfs/super.c:2034
mount_bdev+0x30c/0x3e0 fs/super.c:1174
get_super_block+0x34/0x40 fs/reiserfs/super.c:2605
mount_fs+0xae/0x328 fs/super.c:1277
vfs_kern_mount.part.34+0xd4/0x4d0 fs/namespace.c:1037
vfs_kern_mount fs/namespace.c:1027 [inline]
do_new_mount fs/namespace.c:2518 [inline]
do_mount+0x564/0x3070 fs/namespace.c:2848
ksys_mount+0x12d/0x140 fs/namespace.c:3064
__do_sys_mount fs/namespace.c:3078 [inline]
__se_sys_mount fs/namespace.c:3075 [inline]
__x64_sys_mount+0xbe/0x150 fs/namespace.c:3075
do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45843a
RSP: 002b:00007fc481e97ba8 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000020000000 RCX: 000000000045843a
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007fc481e97bf0
RBP: 0000000000000001 R08: 0000000020013900 R09: 0000000020000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000019
R13: 0000000000000001 R14: 00000000006fed68 R15: 0000000000000000

Showing all locks held in the system:
2 locks held by khungtaskd/894:
#0: 00000000555ac416 (rcu_read_lock){....}, at:
check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
#0: 00000000555ac416 (rcu_read_lock){....}, at: watchdog+0x1ff/0xf60
kernel/hung_task.c:249
#1: 00000000dd73bdbb (tasklist_lock){.+.+}, at:
debug_show_all_locks+0xde/0x34a kernel/locking/lockdep.c:4470
1 lock held by rsyslogd/4380:
#0: 00000000ca6266dd (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x1a9/0x1e0
fs/file.c:766
2 locks held by getty/4470:
#0: 000000001d015e21 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 000000000d332adb (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4471:
#0: 0000000048bf8be6 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 0000000023f3c5d7 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4472:
#0: 000000006b8ddf0c (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 0000000061b8fb1b (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4473:
#0: 000000007a3e9951 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 00000000cc33e1ac (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4474:
#0: 00000000d4d7bced (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 00000000cea9fd89 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4475:
#0: 00000000c455607f (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 0000000074a85a34 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4476:
#0: 000000000dda4794 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 0000000096899971 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by syz-executor0/17586:
#0: 00000000a67274d0 (&type->s_umount_key#20/1){+.+.}, at: alloc_super
fs/super.c:223 [inline]
#0: 00000000a67274d0 (&type->s_umount_key#20/1){+.+.}, at:
sget_userns+0x2dd/0xf00 fs/super.c:516
#1: 000000005e3a2817 (&bdev->bd_mutex){+.+.}, at:
__blkdev_get+0x193/0x13a0 fs/block_dev.c:1460
1 lock held by syz-executor0/17667:
#0: 000000005e3a2817 (&bdev->bd_mutex){+.+.}, at:
__blkdev_get+0x193/0x13a0 fs/block_dev.c:1460
1 lock held by blkid/17605:
#0: 000000005e3a2817 (&bdev->bd_mutex){+.+.}, at:
__blkdev_get+0x193/0x13a0 fs/block_dev.c:1460
3 locks held by syz-executor4/17608:
#0: 00000000777e5516 (&lo->lo_ctl_mutex/1){+.+.}, at: lo_ioctl+0x8d/0x2130
drivers/block/loop.c:1392
#1: 000000005e3a2817 (&bdev->bd_mutex){+.+.}, at:
blkdev_reread_part+0x1e/0x40 block/ioctl.c:192
#2: 00000000a67274d0 (&type->s_umount_key#70){.+.+}, at:
__get_super.part.12+0x20f/0x2e0 fs/super.c:695
1 lock held by syz-executor4/17671:
#0: 000000005e3a2817 (&bdev->bd_mutex){+.+.}, at:
__blkdev_get+0x193/0x13a0 fs/block_dev.c:1460

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

NMI backtrace for cpu 1
CPU: 1 PID: 894 Comm: khungtaskd Not tainted 4.17.0-rc6+ #66
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+0x1b9/0x294 lib/dump_stack.c:113
nmi_cpu_backtrace.cold.4+0x19/0xce lib/nmi_backtrace.c:103
nmi_trigger_cpumask_backtrace+0x151/0x192 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:138 [inline]
check_hung_task kernel/hung_task.c:132 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline]
watchdog+0xc10/0xf60 kernel/hung_task.c:249
kthread+0x345/0x410 kernel/kthread.c:240
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0x6/0x10
arch/x86/include/asm/irqflags.h:54


---
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 syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
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syzbot.

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