INFO: task syz-executor.1:27402 blocked for more than 140 seconds.
      Not tainted 4.19.134-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.1  D29336 27402   6599 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:2828 [inline]
 __schedule+0x887/0x2040 kernel/sched/core.c:3517
 schedule+0x8d/0x1b0 kernel/sched/core.c:3561
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:3619
 __mutex_lock_common kernel/locking/mutex.c:1002 [inline]
 __mutex_lock+0x647/0x1260 kernel/locking/mutex.c:1072
 fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1457
 chrdev_open+0x266/0x770 fs/char_dev.c:423
 do_dentry_open+0x4aa/0x1160 fs/open.c:796
 do_last fs/namei.c:3421 [inline]
 path_openat+0x793/0x2df0 fs/namei.c:3537
 do_filp_open+0x18c/0x3f0 fs/namei.c:3567
 do_sys_open+0x3b3/0x520 fs/open.c:1085
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c369
Code: Bad RIP value.
RSP: 002b:00007f946d0ebc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000021000 RCX: 000000000045c369
RDX: 0000000000000000 RSI: 0000000020000180 RDI: ffffffffffffff9c
RBP: 000000000078bfe8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078bfac
R13: 00007ffe944cd60f R14: 00007f946d0ec9c0 R15: 000000000078bfac

Showing all locks held in the system:
1 lock held by khungtaskd/1085:
 #0: 00000000d9f7b4c4 (rcu_read_lock){....}, at: debug_show_all_locks+0x53/0x265 kernel/locking/lockdep.c:4440
1 lock held by in:imklog/6148:
 #0: 00000000b0e25c7d (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x26f/0x310 fs/file.c:767
2 locks held by agetty/6370:
 #0: 000000003b5a23b8 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:272
 #1: 00000000a40bea2d (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x217/0x1950 drivers/tty/n_tty.c:2154
2 locks held by kworker/u4:0/21315:
3 locks held by syz-executor.1/27332:
1 lock held by syz-executor.1/27402:
 #0: 0000000092a2b51c (&fb_info->lock){+.+.}, at: fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1457

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

NMI backtrace for cpu 1
CPU: 1 PID: 1085 Comm: khungtaskd Not tainted 4.19.134-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+0x1fc/0x2fe lib/dump_stack.c:118
 nmi_cpu_backtrace.cold+0x63/0xa2 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x1a6/0x1eb lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:203 [inline]
 watchdog+0x991/0xe60 kernel/hung_task.c:287
 kthread+0x30b/0x410 kernel/kthread.c:246
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 21315 Comm: kworker/u4:0 Not tainted 4.19.134-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: bat_events batadv_dat_purge
RIP: 0010:hlock_class kernel/locking/lockdep.c:152 [inline]
RIP: 0010:mark_lock+0x66/0x1160 kernel/locking/lockdep.c:3105
Code: c0 74 08 3c 01 0f 8e f1 07 00 00 0f b7 45 20 66 a9 ff 1f 74 7c 48 ba 00 00 00 00 00 fc ff df 4c 89 f1 48 c1 e9 03 0f b6 14 11 <84> d2 74 09 80 fa 03 0f 8e d2 07 00 00 25 ff 1f 00 00 48 69 d8 50
RSP: 0018:ffff88803a8afc00 EFLAGS: 00000802
RAX: 0000000000000699 RBX: 0000000000000001 RCX: 1ffff1100ac23592
RDX: 0000000000000000 RSI: ffff88805611ac70 RDI: ffff88805611a3c0
RBP: ffff88805611ac70 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000040
R13: ffff88805611a3c0 R14: ffff88805611ac90 R15: 0000000000000006
FS:  0000000000000000(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c00046f000 CR3: 000000009f456000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 mark_held_locks+0xa6/0xf0 kernel/locking/lockdep.c:2809
 __trace_hardirqs_on_caller kernel/locking/lockdep.c:2838 [inline]
 lockdep_hardirqs_on+0x3a8/0x5c0 kernel/locking/lockdep.c:2883
 __local_bh_enable_ip+0x159/0x270 kernel/softirq.c:194
 spin_unlock_bh include/linux/spinlock.h:374 [inline]
 __batadv_dat_purge.part.0+0x232/0x330 net/batman-adv/distributed-arp-table.c:151
 __batadv_dat_purge net/batman-adv/distributed-arp-table.c:132 [inline]
 batadv_dat_purge+0x47/0x60 net/batman-adv/distributed-arp-table.c:170
 process_one_work+0x864/0x1570 kernel/workqueue.c:2155
 worker_thread+0x64c/0x1130 kernel/workqueue.c:2298
 kthread+0x30b/0x410 kernel/kthread.c:246
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415