INFO: task hung in con_font_op

Status: upstream: reported on 2026/09/17 11:52
Reported-by: syzbot+fc95047591b2b8fe5b7e@syzkaller.appspotmail.com
First crash: 2d16h, last: 2d16h
Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: task hung in con_font_op 1 1 9d15h 9d15h 0/3 upstream: reported on 2026/09/10 12:27
linux-4.14 INFO: task hung in con_font_op 1 1 2466d 2466d 0/1 auto-closed as invalid on 2020/04/17 20:41
linux-4.19 INFO: task hung in con_font_op 1 3 2331d 2460d 0/1 auto-closed as invalid on 2020/08/30 22:32
upstream INFO: task hung in con_font_op serial 1 2 2305d 2318d 0/29 auto-closed as invalid on 2020/08/26 18:47

Sample crash report:
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
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:
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>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 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
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/17 11:52 linux-5.15.y 0248c33e835e 95928915 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: task hung in con_font_op
* Struck through repros no longer work on HEAD.