Date:   Sun, 23 Feb 2020 22:48:12 -0800
From:   syzbot <syzbot+853639d0cb16c31c7a14@...kaller.appspotmail.com>
To:     linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org,
        miquel.raynal@...tlin.com, richard@....at,
        syzkaller-bugs@...glegroups.com, vigneshr@...com
Subject: INFO: task hung in ubi_detach_mtd_dev

Hello,

syzbot found the following crash on:

HEAD commit:    54dedb5b Merge tag 'for-linus-5.6-rc3-tag' of git://git.ke..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11d81c81e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3b8906eb6a7d6028
dashboard link: https://syzkaller.appspot.com/bug?extid=853639d0cb16c31c7a14
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12037de9e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+853639d0cb16c31c7a14@...kaller.appspotmail.com

INFO: task syz-executor.0:10515 blocked for more than 143 seconds.
      Not tainted 5.6.0-rc2-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.0  D28360 10515      1 0x00004004
Call Trace:
 context_switch kernel/sched/core.c:3380 [inline]
 __schedule+0x934/0x1f90 kernel/sched/core.c:4080
 schedule+0xdc/0x2b0 kernel/sched/core.c:4154
 schedule_timeout+0x717/0xc50 kernel/time/timer.c:1871
 do_wait_for_common kernel/sched/completion.c:83 [inline]
 __wait_for_common kernel/sched/completion.c:104 [inline]
 wait_for_common kernel/sched/completion.c:115 [inline]
 wait_for_completion+0x29c/0x440 kernel/sched/completion.c:136
 kthread_stop+0x187/0x800 kernel/kthread.c:559
 ubi_detach_mtd_dev+0x219/0x43a drivers/mtd/ubi/build.c:1101
 ctrl_cdev_ioctl+0x1d6/0x2d0 drivers/mtd/ubi/cdev.c:1068
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x123/0x180 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:770
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c429
Code: Bad RIP value.
RSP: 002b:00007f8a63950c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f8a639516d4 RCX: 000000000045c429
RDX: 000000000076006e RSI: 0000000040046f41 RDI: 0000000000000003
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000207 R14: 00000000004c3e69 R15: 000000000076bf2c
INFO: task syz-executor.2:10517 blocked for more than 143 seconds.
      Not tainted 5.6.0-rc2-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.2  D28360 10517      1 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:3380 [inline]
 __schedule+0x934/0x1f90 kernel/sched/core.c:4080
 schedule+0xdc/0x2b0 kernel/sched/core.c:4154
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:4213
 __mutex_lock_common kernel/locking/mutex.c:1033 [inline]
 __mutex_lock+0x7ab/0x13c0 kernel/locking/mutex.c:1103
 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1118
 ctrl_cdev_ioctl+0x1cd/0x2d0 drivers/mtd/ubi/cdev.c:1067
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x123/0x180 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:770
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c429
Code: Bad RIP value.
RSP: 002b:00007f0e054ecc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f0e054ed6d4 RCX: 000000000045c429
RDX: 000000000076006e RSI: 0000000040046f41 RDI: 0000000000000003
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000207 R14: 00000000004c3e69 R15: 000000000076bf2c
INFO: task syz-executor.1:10526 blocked for more than 143 seconds.
      Not tainted 5.6.0-rc2-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.1  D28360 10526      1 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:3380 [inline]
 __schedule+0x934/0x1f90 kernel/sched/core.c:4080
 schedule+0xdc/0x2b0 kernel/sched/core.c:4154
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:4213
 __mutex_lock_common kernel/locking/mutex.c:1033 [inline]
 __mutex_lock+0x7ab/0x13c0 kernel/locking/mutex.c:1103
 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1118
 ctrl_cdev_ioctl+0x1cd/0x2d0 drivers/mtd/ubi/cdev.c:1067
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x123/0x180 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:770
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c429
Code: Bad RIP value.
RSP: 002b:00007efcab39fc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007efcab3a06d4 RCX: 000000000045c429
RDX: 000000000076006e RSI: 0000000040046f41 RDI: 0000000000000003
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000207 R14: 00000000004c3e69 R15: 000000000076bf2c
INFO: task syz-executor.5:10531 blocked for more than 144 seconds.
      Not tainted 5.6.0-rc2-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5  D28360 10531      1 0x00004004
Call Trace:
 context_switch kernel/sched/core.c:3380 [inline]
 __schedule+0x934/0x1f90 kernel/sched/core.c:4080
 schedule+0xdc/0x2b0 kernel/sched/core.c:4154
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:4213
 __mutex_lock_common kernel/locking/mutex.c:1033 [inline]
 __mutex_lock+0x7ab/0x13c0 kernel/locking/mutex.c:1103
 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1118
 ctrl_cdev_ioctl+0x1cd/0x2d0 drivers/mtd/ubi/cdev.c:1067
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x123/0x180 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:770
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c429
Code: Bad RIP value.
RSP: 002b:00007f2004611c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f20046126d4 RCX: 000000000045c429
RDX: 000000000076006e RSI: 0000000040046f41 RDI: 0000000000000003
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000207 R14: 00000000004c3e69 R15: 000000000076bf2c
INFO: task syz-executor.5:10535 blocked for more than 144 seconds.
      Not tainted 5.6.0-rc2-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5  D28360 10535      1 0x00004004
Call Trace:
 context_switch kernel/sched/core.c:3380 [inline]
 __schedule+0x934/0x1f90 kernel/sched/core.c:4080
 schedule+0xdc/0x2b0 kernel/sched/core.c:4154
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:4213
 __mutex_lock_common kernel/locking/mutex.c:1033 [inline]
 __mutex_lock+0x7ab/0x13c0 kernel/locking/mutex.c:1103
 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1118
 ctrl_cdev_ioctl+0x22b/0x2d0 drivers/mtd/ubi/cdev.c:1042
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x123/0x180 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:770
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c429
Code: Bad RIP value.
RSP: 002b:00007f20045f0c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f20045f16d4 RCX: 000000000045c429
RDX: 000000000076006e RSI: 0000000040186f40 RDI: 0000000000000004
RBP: 000000000076bfc0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000207 R14: 00000000004c3e69 R15: 000000000076bfcc
INFO: task syz-executor.5:10542 blocked for more than 144 seconds.
      Not tainted 5.6.0-rc2-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5  D28360 10542      1 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:3380 [inline]
 __schedule+0x934/0x1f90 kernel/sched/core.c:4080
 schedule+0xdc/0x2b0 kernel/sched/core.c:4154
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:4213
 __mutex_lock_common kernel/locking/mutex.c:1033 [inline]
 __mutex_lock+0x7ab/0x13c0 kernel/locking/mutex.c:1103
 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1118
 ctrl_cdev_ioctl+0x1cd/0x2d0 drivers/mtd/ubi/cdev.c:1067
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x123/0x180 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:770
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c429
Code: Bad RIP value.
RSP: 002b:00007f20045cfc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f20045d06d4 RCX: 000000000045c429
RDX: 000000000076006e RSI: 0000000040046f41 RDI: 0000000000000003
RBP: 000000000076c060 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000207 R14: 00000000004c3e69 R15: 000000000076c06c
INFO: task syz-executor.3:10537 blocked for more than 144 seconds.
      Not tainted 5.6.0-rc2-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.3  D28360 10537      1 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:3380 [inline]
 __schedule+0x934/0x1f90 kernel/sched/core.c:4080
 schedule+0xdc/0x2b0 kernel/sched/core.c:4154
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:4213
 __mutex_lock_common kernel/locking/mutex.c:1033 [inline]
 __mutex_lock+0x7ab/0x13c0 kernel/locking/mutex.c:1103
 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1118
 ctrl_cdev_ioctl+0x1cd/0x2d0 drivers/mtd/ubi/cdev.c:1067
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x123/0x180 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:770
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c429
Code: Bad RIP value.
RSP: 002b:00007fa602909c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fa60290a6d4 RCX: 000000000045c429
RDX: 000000000076006e RSI: 0000000040046f41 RDI: 0000000000000003
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000207 R14: 00000000004c3e69 R15: 000000000076bf2c
INFO: task syz-executor.3:10540 blocked for more than 144 seconds.
      Not tainted 5.6.0-rc2-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.3  D28360 10540      1 0x00004004
Call Trace:
 context_switch kernel/sched/core.c:3380 [inline]
 __schedule+0x934/0x1f90 kernel/sched/core.c:4080
 schedule+0xdc/0x2b0 kernel/sched/core.c:4154
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:4213
 __mutex_lock_common kernel/locking/mutex.c:1033 [inline]
 __mutex_lock+0x7ab/0x13c0 kernel/locking/mutex.c:1103
 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1118
 ctrl_cdev_ioctl+0x22b/0x2d0 drivers/mtd/ubi/cdev.c:1042
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x123/0x180 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:770
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c429
Code: Bad RIP value.
RSP: 002b:00007fa6028e8c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fa6028e96d4 RCX: 000000000045c429
RDX: 000000000076006e RSI: 0000000040186f40 RDI: 0000000000000004
RBP: 000000000076bfc0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000207 R14: 00000000004c3e69 R15: 000000000076bfcc
INFO: task syz-executor.3:10544 blocked for more than 145 seconds.
      Not tainted 5.6.0-rc2-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.3  D28360 10544      1 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:3380 [inline]
 __schedule+0x934/0x1f90 kernel/sched/core.c:4080
 schedule+0xdc/0x2b0 kernel/sched/core.c:4154
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:4213
 __mutex_lock_common kernel/locking/mutex.c:1033 [inline]
 __mutex_lock+0x7ab/0x13c0 kernel/locking/mutex.c:1103
 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1118
 ctrl_cdev_ioctl+0x1cd/0x2d0 drivers/mtd/ubi/cdev.c:1067
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x123/0x180 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:770
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c429
Code: Bad RIP value.
RSP: 002b:00007fa6028c7c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fa6028c86d4 RCX: 000000000045c429
RDX: 000000000076006e RSI: 0000000040046f41 RDI: 0000000000000003
RBP: 000000000076c060 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000207 R14: 00000000004c3e69 R15: 000000000076c06c
INFO: task syz-executor.4:10538 blocked for more than 145 seconds.
      Not tainted 5.6.0-rc2-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.4  D28360 10538      1 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:3380 [inline]
 __schedule+0x934/0x1f90 kernel/sched/core.c:4080
 schedule+0xdc/0x2b0 kernel/sched/core.c:4154
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:4213
 __mutex_lock_common kernel/locking/mutex.c:1033 [inline]
 __mutex_lock+0x7ab/0x13c0 kernel/locking/mutex.c:1103
 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1118
 ctrl_cdev_ioctl+0x1cd/0x2d0 drivers/mtd/ubi/cdev.c:1067
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x123/0x180 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:770
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c429
Code: Bad RIP value.
RSP: 002b:00007f9d3b12ac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f9d3b12b6d4 RCX: 000000000045c429
RDX: 000000000076006e RSI: 0000000040046f41 RDI: 0000000000000003
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000207 R14: 00000000004c3e69 R15: 000000000076bf2c

Showing all locks held in the system:
1 lock held by khungtaskd/1106:
 #0: ffffffff89bac240 (rcu_read_lock){....}, at: debug_show_all_locks+0x5f/0x279 kernel/locking/lockdep.c:5333
1 lock held by rsyslogd/9451:
 #0: ffff88808bc82e20 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xee/0x110 fs/file.c:821
2 locks held by getty/9541:
 #0: ffff8880a00c1090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
 #1: ffffc900058532e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/9542:
 #0: ffff88809f997090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
 #1: ffffc9000589b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/9543:
 #0: ffff8880a962c090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
 #1: ffffc900058432e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/9544:
 #0: ffff8880a30bc090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
 #1: ffffc9000587c2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/9545:
 #0: ffff88809fa28090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
 #1: ffffc900058672e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/9546:
 #0: ffff888099536090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
 #1: ffffc900058ab2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/9547:
 #0: ffff8880a039e090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
 #1: ffffc900058132e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
1 lock held by syz-executor.0/10515:
 #0: ffffffff8a330480 (ubi_devices_mutex){+.+.}, at: ctrl_cdev_ioctl+0x1cd/0x2d0 drivers/mtd/ubi/cdev.c:1067
1 lock held by syz-executor.2/10517:
 #0: ffffffff8a330480 (ubi_devices_mutex){+.+.}, at: ctrl_cdev_ioctl+0x1cd/0x2d0 drivers/mtd/ubi/cdev.c:1067
1 lock held by syz-executor.1/10526:
 #0: ffffffff8a330480 (ubi_devices_mutex){+.+.}, at: ctrl_cdev_ioctl+0x1cd/0x2d0 drivers/mtd/ubi/cdev.c:1067
1 lock held by syz-executor.5/10531:
 #0: ffffffff8a330480 (ubi_devices_mutex){+.+.}, at: ctrl_cdev_ioctl+0x1cd/0x2d0 drivers/mtd/ubi/cdev.c:1067
1 lock held by syz-executor.5/10535:
 #0: ffffffff8a330480 (ubi_devices_mutex){+.+.}, at: ctrl_cdev_ioctl+0x22b/0x2d0 drivers/mtd/ubi/cdev.c:1042
1 lock held by syz-executor.5/10542:
 #0: ffffffff8a330480 (ubi_devices_mutex){+.+.}, at: ctrl_cdev_ioctl+0x1cd/0x2d0 drivers/mtd/ubi/cdev.c:1067
1 lock held by syz-executor.3/10537:
 #0: ffffffff8a330480 (ubi_devices_mutex){+.+.}, at: ctrl_cdev_ioctl+0x1cd/0x2d0 drivers/mtd/ubi/cdev.c:1067
1 lock held by syz-executor.3/10540:
 #0: ffffffff8a330480 (ubi_devices_mutex){+.+.}, at: ctrl_cdev_ioctl+0x22b/0x2d0 drivers/mtd/ubi/cdev.c:1042
1 lock held by syz-executor.3/10544:
 #0: ffffffff8a330480 (ubi_devices_mutex){+.+.}, at: ctrl_cdev_ioctl+0x1cd/0x2d0 drivers/mtd/ubi/cdev.c:1067
1 lock held by syz-executor.4/10538:
 #0: ffffffff8a330480 (ubi_devices_mutex){+.+.}, at: ctrl_cdev_ioctl+0x1cd/0x2d0 drivers/mtd/ubi/cdev.c:1067
1 lock held by syz-executor.4/10541:
 #0: ffffffff8a330480 (ubi_devices_mutex){+.+.}, at: ctrl_cdev_ioctl+0x22b/0x2d0 drivers/mtd/ubi/cdev.c:1042
1 lock held by syz-executor.4/10546:
 #0: ffffffff8a330480 (ubi_devices_mutex){+.+.}, at: ctrl_cdev_ioctl+0x1cd/0x2d0 drivers/mtd/ubi/cdev.c:1067

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

NMI backtrace for cpu 0
CPU: 0 PID: 1106 Comm: khungtaskd Not tainted 5.6.0-rc2-syzkaller #0
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+0x197/0x210 lib/dump_stack.c:118
 nmi_cpu_backtrace.cold+0x70/0xb2 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x23b/0x28b 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:146 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:205 [inline]
 watchdog+0xb11/0x10c0 kernel/hung_task.c:289
 kthread+0x361/0x430 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:60


---
This bug is generated by a bot. It may contain errors.
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