syzbot
INFO: task hung in tty_release_struct
Status:
upstream: reported on 2026/08/22 05:26
Reported-by: syzbot+334cb50f831c80acc6eb@syzkaller.appspotmail.com
First crash: 6d09h, last: 6d09h
Sample crash report:
INFO: task syz.8.1579:12050 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.8.1579 state:D stack:27400 pid:12050 ppid:8976 flags:0x00004006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5382 [inline]
__schedule+0x15ae/0x4660 kernel/sched/core.c:6701
schedule+0xbd/0x170 kernel/sched/core.c:6775
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6834
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x673/0xc80 kernel/locking/mutex.c:747
tty_release_struct+0xae/0xd0 drivers/tty/tty_io.c:1698
tty_release+0xbcc/0x14f0 drivers/tty/tty_io.c:1859
__fput+0x221/0x940 fs/file_table.c:418
__do_sys_close fs/open.c:1574 [inline]
__se_sys_close+0x15c/0x1e0 fs/open.c:1559
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f9c1b59e0d9
RSP: 002b:00007f9c1c401028 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: ffffffffffffffda RBX: 00007f9c1b826090 RCX: 00007f9c1b59e0d9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f9c1b635024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9c1b826128 R14: 00007f9c1b826090 R15: 00007ffe5e15a548
</TASK>
INFO: task syz.0.1596:12098 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.1596 state:D stack:27912 pid:12098 ppid:5786 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5382 [inline]
__schedule+0x15ae/0x4660 kernel/sched/core.c:6701
schedule+0xbd/0x170 kernel/sched/core.c:6775
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6834
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x673/0xc80 kernel/locking/mutex.c:747
ptmx_open+0xd0/0x2c0 drivers/tty/pty.c:823
chrdev_open+0x58c/0x600 fs/char_dev.c:414
do_dentry_open+0x880/0x14b0 fs/open.c:929
do_open fs/namei.c:3683 [inline]
path_openat+0x284f/0x3270 fs/namei.c:3844
do_filp_open+0x1f2/0x430 fs/namei.c:3871
do_sys_openat2+0x134/0x1d0 fs/open.c:1422
do_sys_open fs/open.c:1437 [inline]
__do_sys_openat fs/open.c:1453 [inline]
__se_sys_openat fs/open.c:1448 [inline]
__x64_sys_openat+0x139/0x160 fs/open.c:1448
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f6211f9e0d9
RSP: 002b:00007f6212e2b028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f6212226090 RCX: 00007f6211f9e0d9
RDX: 0000000000008080 RSI: 00002000000000c0 RDI: ffffffffffffff9c
RBP: 00007f6212035024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6212226128 R14: 00007f6212226090 R15: 00007fffb96215b8
</TASK>
INFO: task syz.7.1655:12263 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.7.1655 state:D stack:25832 pid:12263 ppid:7735 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5382 [inline]
__schedule+0x15ae/0x4660 kernel/sched/core.c:6701
schedule+0xbd/0x170 kernel/sched/core.c:6775
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6834
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x673/0xc80 kernel/locking/mutex.c:747
tty_open_by_driver drivers/tty/tty_io.c:2044 [inline]
tty_open+0x211/0xcc0 drivers/tty/tty_io.c:2127
chrdev_open+0x58c/0x600 fs/char_dev.c:414
do_dentry_open+0x880/0x14b0 fs/open.c:929
do_open fs/namei.c:3683 [inline]
path_openat+0x284f/0x3270 fs/namei.c:3844
do_filp_open+0x1f2/0x430 fs/namei.c:3871
do_sys_openat2+0x134/0x1d0 fs/open.c:1422
do_sys_open fs/open.c:1437 [inline]
__do_sys_openat fs/open.c:1453 [inline]
__se_sys_openat fs/open.c:1448 [inline]
__x64_sys_openat+0x139/0x160 fs/open.c:1448
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7ffa6915e90e
RSP: 002b:00007ffa66f90b28 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007ffa66f916c0 RCX: 00007ffa6915e90e
RDX: 0000000000000002 RSI: 00007ffa66f90c00 RDI: ffffffffffffff9c
RBP: 00007ffa69235024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffa69426308 R14: 00007ffa69426270 R15: 00007ffdac03d488
</TASK>
Showing all locks held in the system:
1 lock held by khungtaskd/29:
#0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
#0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
#0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
3 locks held by kworker/u4:8/2946:
2 locks held by getty/5533:
#0: ffff8880313720a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc9000325e2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x428/0x1370 drivers/tty/n_tty.c:2217
4 locks held by syz.8.1579/12047:
1 lock held by syz.8.1579/12050:
#0: ffffffff8d8b6d68 (tty_mutex){+.+.}-{3:3}, at: tty_release_struct+0xae/0xd0 drivers/tty/tty_io.c:1698
1 lock held by syz.0.1596/12098:
#0: ffffffff8d8b6d68 (tty_mutex){+.+.}-{3:3}, at: ptmx_open+0xd0/0x2c0 drivers/tty/pty.c:823
1 lock held by syz.7.1655/12263:
#0: ffffffff8d8b6d68 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2044 [inline]
#0: ffffffff8d8b6d68 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x211/0xcc0 drivers/tty/tty_io.c:2127
1 lock held by syz.2.1678/12391:
#0: ffffffff8d8b6d68 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2044 [inline]
#0: ffffffff8d8b6d68 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x211/0xcc0 drivers/tty/tty_io.c:2127
4 locks held by syz-executor/12969:
1 lock held by syz.4.1940/13468:
2 locks held by syz-executor/13630:
1 lock held by dhcpcd-run-hook/13727:
=============================================
NMI backtrace for cpu 0
CPU: 0 PID: 29 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<TASK>
dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
nmi_cpu_backtrace+0x3a6/0x3e0 lib/nmi_backtrace.c:113
nmi_trigger_cpumask_backtrace+0x17a/0x2f0 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline]
watchdog+0xf59/0xfa0 kernel/hung_task.c:379
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>
Struck through repros no longer work on HEAD.