INFO: task syz.0.18:6400 blocked for more
INFO: task syz.0.18:6400 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.18 state:D stack:27328 pid:6400 tgid:6399 ppid:6286 task_flags:0x400140 flags:0x00080003
Call Trace:
context_switch kernel/sched/core.c:5521 [inline]
__schedule+0x1b57/0x5bc0 kernel/sched/core.c:7272
__schedule_loop kernel/sched/core.c:7349 [inline]
schedule+0x164/0x2b0 kernel/sched/core.c:7364
schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7421
__mutex_lock_common kernel/locking/mutex.c:726 [inline]
__mutex_lock+0x7c1/0x1550 kernel/locking/mutex.c:821
bdev_release+0x1b8/0x690 block/bdev.c:1173
blkdev_release+0x15/0x20 block/fops.c:682
__fput+0x418/0xa50 fs/file_table.c:512
task_work_run+0x1d9/0x270 kernel/task_work.c:233
get_signal+0x1181/0x12c0 kernel/signal.c:2811
arch_do_signal_or_restart+0xbb/0x860 arch/x86/kernel/signal.c:337
__exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
exit_to_user_mode_loop+0x10e/0x770 kernel/entry/common.c:101
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:336 [inline]
do_syscall_64+0x328/0x520 arch/x86/entry/syscall_64.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe7bc99a379
RSP: 002b:00007fe7bd85a028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: 0000000000000000 RBX: 00007fe7bcbd5fa0 RCX: 00007fe7bc99a379
RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000003
RBP: 00007fe7bca2dd68 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe7bcbd6038 R14: 00007fe7bcbd5fa0 R15: 00007ffd06057568
Showing all locks held in the system:
locks held by pr/ttyS0/16: 2, last CPU#1:
#0: ffffffff8ec36638 (console_srcu){....}-{0:0}, at: rcu_try_lock_acquire include/linux/rcupdate.h:314 [inline]
#0: ffffffff8ec36638 (console_srcu){....}-{0:0}, at: srcu_read_lock_nmisafe include/linux/srcu.h:439 [inline]
#0: ffffffff8ec36638 (console_srcu){....}-{0:0}, at: console_srcu_read_lock+0x30/0x60 kernel/printk/printk.c:291
#1: ffffffff9ad2f0b8 (&port_lock_key){-.-.}-{3:3}, at: __uart_port_lock_irqsave include/linux/serial_core.h:613 [inline]
#1: ffffffff9ad2f0b8 (&port_lock_key){-.-.}-{3:3}, at: univ8250_console_device_lock+0x67/0xc0 drivers/tty/serial/8250/8250_core.c:413
locks held by khungtaskd/32: 1, last CPU#0:
#0: ffffffff8ed5ca60 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
#0: ffffffff8ed5ca60 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
#0: ffffffff8ed5ca60 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6837
locks held by getty/5374: 2, on CPU#0:
#0: ffff888033e7e0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc9000322b2e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45a/0x1360 drivers/tty/n_tty.c:2211
locks held by udevd/6087: 1, on CPU#0:
#0: ffff888026f3c350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xde/0xd70 block/bdev.c:990
locks held by udevd/6260: 1, on CPU#0:
#0: ffff888026f37350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xde/0xd70 block/bdev.c:990
locks held by syz.0.18/6400: 1, on CPU#0:
#0: ffff888026f3c350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_release+0x1b8/0x690 block/bdev.c:1173
locks held by syz.1.19/6436: 1, on CPU#0:
#0: ffff888027400350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_release+0x1b8/0x690 block/bdev.c:1173
locks held by udevd/6437: 1, on CPU#1:
#0: ffff888027400350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xde/0xd70 block/bdev.c:990
locks held by udevd/6441: 1, on CPU#1:
#0: ffff888027404350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xde/0xd70 block/bdev.c:990
locks held by syz.2.21/6477: 1, on CPU#1:
#0: ffff888027404350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_release+0x1b8/0x690 block/bdev.c:1173
locks held by udevd/6487: 1, on CPU#0:
#0: ffff8880274df350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xde/0xd70 block/bdev.c:990
locks held by syz.3.23/6522: 1, on CPU#0:
#0: ffff8880274df350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_release+0x1b8/0x690 block/bdev.c:1173
locks held by udevd/6565: 1, on CPU#1:
#0: ffff888026f33350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xde/0xd70 block/bdev.c:990
locks held by syz.4.26/6569: 1, on CPU#1:
#0: ffff888026f33350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_release+0x1b8/0x690 block/bdev.c:1173
locks held by udevd/6573: 1, on CPU#0:
#0: ffff888027481350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xde/0xd70 block/bdev.c:990
locks held by syz.5.28/6614: 1, on CPU#1:
#0: ffff888026f37350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_release+0x1b8/0x690 block/bdev.c:1173
locks held by udevd/6618: 1, on CPU#1:
#0: ffff888026d1b350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xde/0xd70 block/bdev.c:990
locks held by syz.6.29/6657: 1, on CPU#1:
#0: ffff888026d1b350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_release+0x1b8/0x690 block/bdev.c:1173
locks held by syz.7.30/6705: 1, on CPU#1:
#0: ffff888026d1f350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_release+0x1b8/0x690 block/bdev.c:1173
locks held by udevd/6706: 1, on CPU#0:
#0: ffff888026d1f350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xde/0xd70 block/bdev.c:990
locks held by syz.8.31/6749: 1, on CPU#1:
#0: ffff888027481350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_release+0x1b8/0x690 block/bdev.c:1173
=============================================
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 32 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:123
nmi_trigger_cpumask_backtrace+0x17d/0x390 lib/nmi_backtrace.c:66
trigger_all_cpu_backtrace include/linux/nmi.h:164 [inline]
__sys_info lib/sys_info.c:157 [inline]
sys_info+0x135/0x170 lib/sys_info.c:165
check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
watchdog+0xfd7/0x1030 kernel/hung_task.c:561
kthread+0x38b/0x480 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 16 Comm: pr/ttyS0 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:io_serial_in+0x77/0xc0 drivers/tty/serial/8250/8250_port.c:409
Code: e8 4e 7e 56 fc 44 89 f9 d3 e3 49 83 c6 40 4c 89 f0 48 c1 e8 03 42 80 3c 20 00 74 08 4c 89 f7 e8 ef 48 c6 fc 41 03 1e 89 da ec <0f> b6 c0 5b 41 5c 41 5e 41 5f e9 9a 9a 74 06 cc 44 89 f9 80 e1 07
RSP: 0018:ffffc900001578b8 EFLAGS: 00000002
RAX: 1ffffffff35a5e00 RBX: 00000000000003fd RCX: 0000000000000000
RDX: 00000000000003fd RSI: 0000000000000000 RDI: 0000000000000020
RBP: dffffc0000000000 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: ffffffff85714080 R12: dffffc0000000000
R13: 0000000000000000 R14: ffffffff9ad2f0e0 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff888124ddc000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f779d7e7ac0 CR3: 000000000eb48000 CR4: 00000000003526f0
Call Trace:
serial_in drivers/tty/serial/8250/8250.h:128 [inline]
serial_lsr_in drivers/tty/serial/8250/8250.h:150 [inline]
wait_for_lsr+0x184/0x2f0 drivers/tty/serial/8250/8250_port.c:2013
serial8250_fifo_wait_for_lsr_thre drivers/tty/serial/8250/8250_port.c:3270 [inline]
__serial8250_console_fifo_write+0xcd/0x3e0 drivers/tty/serial/8250/8250_port.c:3345
serial8250_console_fifo_write drivers/tty/serial/8250/8250_port.c:3378 [inline]
__serial8250_console_write drivers/tty/serial/8250/8250_port.c:3429 [inline]
serial8250_console_write+0xaa1/0x1200 drivers/tty/serial/8250/8250_port.c:3493
nbcon_emit_next_record+0xef5/0x1a90 kernel/printk/nbcon.c:-1
nbcon_emit_one kernel/printk/nbcon.c:1157 [inline]
nbcon_kthread_func+0x679/0x880 kernel/printk/nbcon.c:1271
kthread+0x38b/0x480 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245