[syzbot] [kernel?] INFO: task hung in vcs_open (10)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e7ae89a0c97c Linux 7.1-rc5
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11d8c62e580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e327ee9a867dd6b9
dashboard link: https://syzkaller.appspot.com/bug?extid=99897fb26901360e1e8e
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bbe0fa53b9f3/disk-e7ae89a0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8a6e244da62c/vmlinux-e7ae89a0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/eb16b1c79be7/bzImage-e7ae89a0.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+99897f...@syzkaller.appspotmail.com

INFO: task syz.9.2438:15503 blocked for more than 143 seconds.
Tainted: G L syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.9.2438 state:D stack:26792 pid:15503 tgid:15501 ppid:14199 task_flags:0x400140 flags:0x00080002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5388 [inline]
__schedule+0x1295/0x67a0 kernel/sched/core.c:7189
__schedule_loop kernel/sched/core.c:7268 [inline]
schedule+0xdd/0x390 kernel/sched/core.c:7283
schedule_timeout+0x1b2/0x280 kernel/time/sleep_timeout.c:75
___down_common kernel/locking/semaphore.c:289 [inline]
__down_common+0x371/0x8a0 kernel/locking/semaphore.c:314
down+0x74/0xa0 kernel/locking/semaphore.c:100
console_lock+0x5b/0xa0 kernel/printk/printk.c:2896
class_console_lock_constructor include/linux/console.h:736 [inline]
vcs_open+0x64/0xc0 drivers/tty/vt/vc_screen.c:746
chrdev_open+0x234/0x6a0 fs/char_dev.c:411
do_dentry_open+0x6d8/0x1660 fs/open.c:947
vfs_open+0x82/0x3f0 fs/open.c:1079
do_open fs/namei.c:4699 [inline]
path_openat+0x208c/0x31a0 fs/namei.c:4858
do_file_open+0x20e/0x430 fs/namei.c:4887
do_sys_openat2+0x10d/0x1e0 fs/open.c:1364
do_sys_open fs/open.c:1370 [inline]
__do_sys_openat fs/open.c:1386 [inline]
__se_sys_openat fs/open.c:1381 [inline]
__x64_sys_openat+0x12d/0x210 fs/open.c:1381
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x10b/0x860 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa79339ce59
RSP: 002b:00007fa794264028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fa793615fa0 RCX: 00007fa79339ce59
RDX: 0000000000000040 RSI: 0000200000000100 RDI: ffffffffffffff9c
RBP: 00007fa793432d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa793616038 R14: 00007fa793615fa0 R15: 00007ffefb5dd5d8
</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/30:
#0: ffffffff8e7e5620 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
#0: ffffffff8e7e5620 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
#0: ffffffff8e7e5620 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x3d/0x184 kernel/locking/lockdep.c:6775
2 locks held by getty/5365:
#0: ffff888039d210a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
#1: ffffc900032332e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x419/0x14f0 drivers/tty/n_tty.c:2211
2 locks held by kworker/0:7/5804:
6 locks held by syz.2.1808/12584:
4 locks held by syz-executor/16651:
2 locks held by syz.6.2786/17075:
#0: ffffffff8f5023c0 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline]
#0: ffffffff8f5023c0 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x539/0xfa0 drivers/tty/tty_io.c:2120
#1: ffff8880261a61b0 (&tty->legacy_mutex){+.+.}-{4:4}, at: tty_init_dev.part.0+0x39/0x470 drivers/tty/tty_io.c:1406
1 lock held by syz.2.2827/17451:
#0: ffffffff8f5023c0 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline]
#0: ffffffff8f5023c0 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x539/0xfa0 drivers/tty/tty_io.c:2120
1 lock held by syz.1.2888/17504:
1 lock held by syz.7.2903/17552:
1 lock held by syz.8.2907/17560:
#0: ffff88807e610dc8 (&ima_iint_mutex_key[depth]){+.+.}-{4:4}, at: ima_check_last_writer security/integrity/ima/ima_main.c:215 [inline]
#0: ffff88807e610dc8 (&ima_iint_mutex_key[depth]){+.+.}-{4:4}, at: ima_file_free+0x146/0x340 security/integrity/ima/ima_main.c:251
1 lock held by syz.8.2907/17566:

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 30 Comm: khungtaskd Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
nmi_cpu_backtrace.cold+0x12d/0x151 lib/nmi_backtrace.c:113
nmi_trigger_cpumask_backtrace+0x1d7/0x230 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline]
__sys_info lib/sys_info.c:157 [inline]
sys_info+0x141/0x190 lib/sys_info.c:165
check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
watchdog+0xcb1/0x1030 kernel/hung_task.c:561
kthread+0x370/0x450 kernel/kthread.c:436
ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:63
Code: 56 92 02 c3 cc cc cc cc 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 43 41 20 00 fb f4 <e9> 7c 42 03 00 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90
RSP: 0018:ffffc90000197df0 EFLAGS: 00000246
RAX: 0000000005d0e9e7 RBX: ffff88801e2ca500 RCX: ffffffff8b8b50b5
RDX: 0000000000000000 RSI: ffffffff8df24460 RDI: ffffffff8c1c4500
RBP: 0000000000000000 R08: 0000000000000001 R09: ffffed10170a67b5
R10: ffff8880b8533dab R11: 0000000000000000 R12: 0000000000000001
R13: ffffed1003c594a0 R14: 0000000000000001 R15: ffffffff90d7e950
FS: 0000000000000000(0000) GS:ffff88812446a000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc8e89456b8 CR3: 0000000043fd1000 CR4: 00000000003526f0
Call Trace:
<TASK>
arch_safe_halt arch/x86/include/asm/paravirt.h:62 [inline]
default_idle+0x9/0x10 arch/x86/kernel/process.c:767
default_idle_call+0x6c/0xb0 kernel/sched/idle.c:122
cpuidle_idle_call kernel/sched/idle.c:199 [inline]
do_idle+0x464/0x590 kernel/sched/idle.c:352
cpu_startup_entry+0x4f/0x60 kernel/sched/idle.c:451
start_secondary+0x21d/0x2d0 arch/x86/kernel/smpboot.c:312
common_startup_64+0x13e/0x148
</TASK>


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