[v6.1] INFO: task hung in con_font_op
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syzbot
Sep 10, 2026, 8:27:26 AMSep 10
to syzkaller...@googlegroups.com
Hello,
syzbot found the following issue on:
HEAD commit: cf82dcca9634 Linux 6.1.187
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10e30905580000
kernel config: https://syzkaller.appspot.com/x/.config?x=31dfefc4a14efea3
dashboard link: https://syzkaller.appspot.com/bug?extid=537908831b6690fbd537
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/97e1e40b968b/disk-cf82dcca.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cfec27562c15/vmlinux-cf82dcca.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4c7cd066c46d/bzImage-cf82dcca.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+537908...@syzkaller.appspotmail.com
INFO: task syz.3.3840:15772 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.3840 state:D stack:29136 pid:15772 ppid:4280 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5246 [inline]
__schedule+0x107f/0x4030 kernel/sched/core.c:6563
schedule+0xb9/0x180 kernel/sched/core.c:6639
schedule_timeout+0xbd/0x2d0 kernel/time/timer.c:2144
___down_common kernel/locking/semaphore.c:229 [inline]
__down_common+0x30c/0x740 kernel/locking/semaphore.c:250
down+0x7c/0xd0 kernel/locking/semaphore.c:64
console_lock+0x141/0x1c0 kernel/printk/printk.c:2629
con_font_default drivers/tty/vt/vt.c:4701 [inline]
con_font_op+0x2dd/0xdb0 drivers/tty/vt/vt.c:4728
vt_k_ioctl drivers/tty/vt/vt_ioctl.c:476 [inline]
vt_ioctl+0x161e/0x1ca0 drivers/tty/vt/vt_ioctl.c:754
tty_ioctl+0x7e6/0xba0 drivers/tty/tty_io.c:2776
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f559399e159
RSP: 002b:00007f55948f7028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f5593c26090 RCX: 00007f559399e159
RDX: 0000200000000e40 RSI: 0000000000004b72 RDI: 0000000000000003
RBP: 00007f5593a3503b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5593c26128 R14: 00007f5593c26090 R15: 00007ffd2068f718
</TASK>
Showing all locks held in the system:
3 locks held by kworker/u4:0/9:
3 locks held by kworker/u4:1/11:
1 lock held by rcu_tasks_kthre/12:
#0: ffffffff8cb2e5b0 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xef0 kernel/rcu/tasks.h:517
1 lock held by rcu_tasks_trace/13:
#0: ffffffff8cb2edd0 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xef0 kernel/rcu/tasks.h:517
1 lock held by khungtaskd/27:
#0: ffffffff8cb2dc20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
#0: ffffffff8cb2dc20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
#0: ffffffff8cb2dc20 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6527
1 lock held by udevd/3639:
2 locks held by getty/4028:
#0: ffff88814cf93098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:244
#1: ffffc9000327b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x41e/0x1360 drivers/tty/n_tty.c:2198
3 locks held by udevd/4365:
2 locks held by kworker/0:9/4379:
#0: ffff888017470938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
#1: ffffc90004937d00 (console_work){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
3 locks held by kworker/0:16/5127:
2 locks held by kworker/0:29/5140:
#0: ffff888017472138 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
#1: ffffc9000daf7d00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
1 lock held by syz-executor/8545:
1 lock held by syz.7.3632/14962:
5 locks held by syz.3.3840/15766:
1 lock held by syz.2.3868/15853:
3 locks held by syz-executor/16077:
1 lock held by syz-executor/17779:
#0: ffffffff8cb338f8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:291 [inline]
#0: ffffffff8cb338f8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x2ec/0x890 kernel/rcu/tree_exp.h:962
2 locks held by syz.5.4703/18713:
1 lock held by dhcpcd-run-hook/18715:
=============================================
NMI backtrace for cpu 0
CPU: 0 PID: 27 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+0x188/0x24e lib/dump_stack.c:106
nmi_cpu_backtrace+0x3e6/0x460 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x1d4/0x450 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:220 [inline]
watchdog+0xf0e/0xf50 kernel/hung_task.c:377
kthread+0x29d/0x330 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
---
This report 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 syzk...@googlegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
syzbot found the following issue on:
HEAD commit: cf82dcca9634 Linux 6.1.187
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10e30905580000
kernel config: https://syzkaller.appspot.com/x/.config?x=31dfefc4a14efea3
dashboard link: https://syzkaller.appspot.com/bug?extid=537908831b6690fbd537
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/97e1e40b968b/disk-cf82dcca.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cfec27562c15/vmlinux-cf82dcca.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4c7cd066c46d/bzImage-cf82dcca.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+537908...@syzkaller.appspotmail.com
INFO: task syz.3.3840:15772 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.3840 state:D stack:29136 pid:15772 ppid:4280 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5246 [inline]
__schedule+0x107f/0x4030 kernel/sched/core.c:6563
schedule+0xb9/0x180 kernel/sched/core.c:6639
schedule_timeout+0xbd/0x2d0 kernel/time/timer.c:2144
___down_common kernel/locking/semaphore.c:229 [inline]
__down_common+0x30c/0x740 kernel/locking/semaphore.c:250
down+0x7c/0xd0 kernel/locking/semaphore.c:64
console_lock+0x141/0x1c0 kernel/printk/printk.c:2629
con_font_default drivers/tty/vt/vt.c:4701 [inline]
con_font_op+0x2dd/0xdb0 drivers/tty/vt/vt.c:4728
vt_k_ioctl drivers/tty/vt/vt_ioctl.c:476 [inline]
vt_ioctl+0x161e/0x1ca0 drivers/tty/vt/vt_ioctl.c:754
tty_ioctl+0x7e6/0xba0 drivers/tty/tty_io.c:2776
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f559399e159
RSP: 002b:00007f55948f7028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f5593c26090 RCX: 00007f559399e159
RDX: 0000200000000e40 RSI: 0000000000004b72 RDI: 0000000000000003
RBP: 00007f5593a3503b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5593c26128 R14: 00007f5593c26090 R15: 00007ffd2068f718
</TASK>
Showing all locks held in the system:
3 locks held by kworker/u4:0/9:
3 locks held by kworker/u4:1/11:
1 lock held by rcu_tasks_kthre/12:
#0: ffffffff8cb2e5b0 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xef0 kernel/rcu/tasks.h:517
1 lock held by rcu_tasks_trace/13:
#0: ffffffff8cb2edd0 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xef0 kernel/rcu/tasks.h:517
1 lock held by khungtaskd/27:
#0: ffffffff8cb2dc20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
#0: ffffffff8cb2dc20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
#0: ffffffff8cb2dc20 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6527
1 lock held by udevd/3639:
2 locks held by getty/4028:
#0: ffff88814cf93098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:244
#1: ffffc9000327b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x41e/0x1360 drivers/tty/n_tty.c:2198
3 locks held by udevd/4365:
2 locks held by kworker/0:9/4379:
#0: ffff888017470938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
#1: ffffc90004937d00 (console_work){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
3 locks held by kworker/0:16/5127:
2 locks held by kworker/0:29/5140:
#0: ffff888017472138 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
#1: ffffc9000daf7d00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
1 lock held by syz-executor/8545:
1 lock held by syz.7.3632/14962:
5 locks held by syz.3.3840/15766:
1 lock held by syz.2.3868/15853:
3 locks held by syz-executor/16077:
1 lock held by syz-executor/17779:
#0: ffffffff8cb338f8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:291 [inline]
#0: ffffffff8cb338f8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x2ec/0x890 kernel/rcu/tree_exp.h:962
2 locks held by syz.5.4703/18713:
1 lock held by dhcpcd-run-hook/18715:
=============================================
NMI backtrace for cpu 0
CPU: 0 PID: 27 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+0x188/0x24e lib/dump_stack.c:106
nmi_cpu_backtrace+0x3e6/0x460 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x1d4/0x450 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:220 [inline]
watchdog+0xf0e/0xf50 kernel/hung_task.c:377
kthread+0x29d/0x330 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
---
This report 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 syzk...@googlegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
syzbot
Sep 17, 2026, 7:52:36 AMSep 17
to syzkaller...@googlegroups.com
Hello,
syzbot found the following issue on:
HEAD commit: 0248c33e835e Linux 5.15.221
syzbot found the following issue on:
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=124f3bf9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=21845b39f8fc6be8
dashboard link: https://syzkaller.appspot.com/bug?extid=fc95047591b2b8fe5b7e
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cdcbd8738a16/disk-0248c33e.raw.xz
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
vmlinux: https://storage.googleapis.com/syzbot-assets/864175e96c3d/vmlinux-0248c33e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/cb031d3f4011/bzImage-0248c33e.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
INFO: task syz.6.732:7500 blocked for more than 144 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.6.732 state:D stack:27888 pid: 7500 ppid: 6889 flags:0x00004004
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11c3/0x4350 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
schedule_timeout+0xbd/0x2d0 kernel/time/timer.c:2093
__down_common+0x289/0x3b0 kernel/locking/semaphore.c:228
down+0x7e/0xd0 kernel/locking/semaphore.c:63
console_lock+0x29/0x70 kernel/printk/printk.c:2557
con_font_set drivers/tty/vt/vt.c:4663 [inline]
con_font_op+0x8d9/0xdc0 drivers/tty/vt/vt.c:4715
vt_k_ioctl drivers/tty/vt/vt_ioctl.c:476 [inline]
vt_ioctl+0x1618/0x1ca0 drivers/tty/vt/vt_ioctl.c:754
tty_ioctl+0x848/0xc30 drivers/tty/tty_io.c:2810
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fc1f5902159
RSP: 002b:00007fc1f3b18028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fc1f5b8a180 RCX: 00007fc1f5902159
RDX: 00002000000001c0 RSI: 0000000000004b72 RDI: 0000000000000005
RBP: 00007fc1f599906b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc1f5b8a218 R14: 00007fc1f5b8a180 R15: 00007ffde52ed538
</TASK>
Showing all locks held in the system:
Showing all locks held in the system:
1 lock held by khungtaskd/27:
#0: ffffffff8c31ef60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
2 locks held by getty/3945:
#0: ffff88814d83e098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
#1: ffffc900025e62e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x594/0x1a50 drivers/tty/n_tty.c:2158
4 locks held by kworker/u4:8/4348:
2 locks held by kworker/u4:10/4354:
2 locks held by kworker/0:10/4406:
1 lock held by syz.3.724/7462:
1 lock held by syz-executor/8253:
6 locks held by syz.8.974/8606:
1 lock held by syz.4.976/8611:
=============================================
NMI backtrace for cpu 0
CPU: 0 PID: 27 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<TASK>
nmi_cpu_backtrace+0x3a2/0x3d0 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:212 [inline]
watchdog+0xe1b/0xe60 kernel/hung_task.c:369
kthread+0x42e/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
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