[v5.15] INFO: task hung in comedi_open

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 68efe5a6c16a Linux 5.15.197
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=137359c2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7e6ed99963d6ee1d
dashboard link: https://syzkaller.appspot.com/bug?extid=f2f4686fdb22d0d3d598
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/900f9b9bd850/disk-68efe5a6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1e089a5019a6/vmlinux-68efe5a6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b319f477b907/bzImage-68efe5a6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f2f468...@syzkaller.appspotmail.com

INFO: task syz.0.707:7927 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.707 state:D stack:27872 pid: 7927 ppid: 4184 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6537
__mutex_lock_common+0xc71/0x2390 kernel/locking/mutex.c:669
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
chrdev_open+0x597/0x670 fs/char_dev.c:414
do_dentry_open+0x7ff/0xf80 fs/open.c:826
do_open fs/namei.c:3616 [inline]
path_openat+0x2682/0x2f30 fs/namei.c:3750
do_filp_open+0x1b3/0x3e0 fs/namei.c:3777
do_sys_openat2+0x142/0x4a0 fs/open.c:1255
do_sys_open fs/open.c:1271 [inline]
__do_sys_openat fs/open.c:1287 [inline]
__se_sys_openat fs/open.c:1282 [inline]
__x64_sys_openat+0x135/0x160 fs/open.c:1282
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: 0033:0x7f2bc5283749
RSP: 002b:00007f2bc34ea038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f2bc54d9fa0 RCX: 00007f2bc5283749
RDX: 0000000000000400 RSI: 0000200000000080 RDI: ffffffffffffff9c
RBP: 00007f2bc5307f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2bc54da038 R14: 00007f2bc54d9fa0 R15: 00007ffe1aef5988
</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/27:
#0: ffffffff8c11c720 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
2 locks held by dhcpcd/3853:
#0: ffffffff8d28f190 (cb_lock){++++}-{3:3}, at: genl_rcv+0x15/0x40 net/netlink/genetlink.c:802
#1: ffffffff8d232788 (rtnl_mutex){+.+.}-{3:3}, at: nl80211_pre_doit+0x28/0x540 net/wireless/nl80211.c:14969
2 locks held by getty/3949:
#0: ffff88802c43f098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
#1: ffffc90002cf62e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x5ba/0x1a30 drivers/tty/n_tty.c:2158
3 locks held by kworker/0:5/4261:
#0: ffff888016870938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
#1: ffffc9000323fd00 ((work_completion)(&(&nsim_dev->trap_data->trap_report_dw)->work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
#2: ffff888141ba3400 (&nsim_dev->port_list_lock#2){+.+.}-{3:3}, at: nsim_dev_trap_report_work+0x56/0xb40 drivers/net/netdevsim/dev.c:757
3 locks held by kworker/u4:12/4426:
4 locks held by udevd/4475:
#0: ffff88807a954540 (&p->lock){+.+.}-{3:3}, at: seq_read_iter+0xad/0xd50 fs/seq_file.c:182
#1: ffff8880202ec488 (&of->mutex){+.+.}-{3:3}, at: kernfs_seq_start+0x51/0x3c0 fs/kernfs/file.c:112
#2: ffff88806240fda0 (kn->active#32){++++}-{0:0}, at: kernfs_seq_start+0x71/0x3c0 fs/kernfs/file.c:113
#3: ffff88807de9b220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:764 [inline]
#3: ffff88807de9b220 (&dev->mutex){....}-{3:3}, at: uevent_show+0x17a/0x330 drivers/base/core.c:2408
1 lock held by udevd/4476:
#0: ffff8880202ce118 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev+0x157/0xa60 block/bdev.c:820
3 locks held by kworker/u4:13/4520:
5 locks held by kworker/1:13/5299:
#0: ffff8881421fdd38 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
#1: ffffc90003a5fd00 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
#2: ffff8880240c3220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:764 [inline]
#2: ffff8880240c3220 (&dev->mutex){....}-{3:3}, at: hub_event+0x1a7/0x5560 drivers/usb/core/hub.c:5827
#3: ffff88807de9b220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:764 [inline]
#3: ffff88807de9b220 (&dev->mutex){....}-{3:3}, at: __device_attach+0x85/0x460 drivers/base/dd.c:954
#4: ffff88807a2aa1a8 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:764 [inline]
#4: ffff88807a2aa1a8 (&dev->mutex){....}-{3:3}, at: __device_attach+0x85/0x460 drivers/base/dd.c:954
2 locks held by kworker/0:10/5746:
#0: ffff888016872138 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
#1: ffffc90003f5fd00 ((work_completion)(&rew.rew_work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
1 lock held by syz.3.492/7001:
1 lock held by syz.0.707/7927:
#0: ffff88802ac508f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.9.1108/10273:
#0: ffff88802ac508f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
3 locks held by syz-executor/10625:
#0: ffffffff8d28f190 (cb_lock){++++}-{3:3}, at: genl_rcv+0x15/0x40 net/netlink/genetlink.c:802
#1: ffffffff8d28efe8 (genl_mutex){+.+.}-{3:3}, at: genl_lock net/netlink/genetlink.c:33 [inline]
#1: ffffffff8d28efe8 (genl_mutex){+.+.}-{3:3}, at: genl_rcv_msg+0x137/0xf40 net/netlink/genetlink.c:790
#2: ffffffff8d232788 (rtnl_mutex){+.+.}-{3:3}, at: wg_set_device+0xf2/0x1e70 drivers/net/wireguard/netlink.c:504
4 locks held by syz-executor/10628:
#0: ffff88807f144460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x28a/0xd00 fs/read_write.c:590
#1: ffff888060e60888 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
#2: ffff888147c4c578 (kn->active#297){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:288
#3: ffffffff8cb72648 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: new_device_store+0x13c/0x740 drivers/net/netdevsim/bus.c:295
8 locks held by syz-executor/10643:
#0: ffff88807f144460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x28a/0xd00 fs/read_write.c:590
#1: ffff888023087488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
#2: ffff888147c4c660 (kn->active#296){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:288
#3: ffffffff8cb72648 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xce/0x380 drivers/net/netdevsim/bus.c:344
#4: ffff88814c509178 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:764 [inline]
#4: ffff88814c509178 (&dev->mutex){....}-{3:3}, at: __device_driver_lock drivers/base/dd.c:1044 [inline]
#4: ffff88814c509178 (&dev->mutex){....}-{3:3}, at: device_release_driver_internal+0xb0/0x750 drivers/base/dd.c:1259
#5: ffff888141ba3400 (&nsim_dev->port_list_lock#2){+.+.}-{3:3}, at: nsim_dev_port_del_all drivers/net/netdevsim/dev.c:1359 [inline]
#5: ffff888141ba3400 (&nsim_dev->port_list_lock#2){+.+.}-{3:3}, at: nsim_dev_reload_destroy+0x115/0x240 drivers/net/netdevsim/dev.c:1561
#6: ffffffff8d232788 (rtnl_mutex){+.+.}-{3:3}, at: nsim_destroy+0x3b/0x150 drivers/net/netdevsim/netdev.c:381
#7: ffffffff8c1211a8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:290 [inline]
#7: ffffffff8c1211a8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x347/0x6b0 kernel/rcu/tree_exp.h:845
2 locks held by syz.8.1162/10727:
#0: ffffffff8d28f190 (cb_lock){++++}-{3:3}, at: genl_rcv+0x15/0x40 net/netlink/genetlink.c:802
#1: ffffffff8d28efe8 (genl_mutex){+.+.}-{3:3}, at: genl_lock net/netlink/genetlink.c:33 [inline]
#1: ffffffff8d28efe8 (genl_mutex){+.+.}-{3:3}, at: genl_rcv_msg+0x137/0xf40 net/netlink/genetlink.c:790
2 locks held by syz.3.1164/10724:
#0: ffff8880202ce118 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_put+0xf9/0x7d0 block/bdev.c:915
#1: ffff88802046e468 (&lo->lo_mutex){+.+.}-{3:3}, at: lo_release+0x4d/0x1f0 drivers/block/loop.c:2071

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

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 10/25/2025
Call Trace:
<TASK>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
nmi_cpu_backtrace+0x397/0x3d0 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+0xe0f/0xe50 kernel/hung_task.c:369
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 4426 Comm: kworker/u4:12 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: phy5 ieee80211_iface_work
RIP: 0010:ieee802_11_find_bssid_profile net/mac80211/util.c:1410 [inline]
RIP: 0010:ieee802_11_parse_elems_crc+0x297/0x10c0 net/mac80211/util.c:1489
Code: 20 84 c0 48 89 7c 24 18 0f 85 89 08 00 00 44 0f b6 3f 4d 8d 6f 02 4c 89 f7 4c 89 ee e8 22 ed 3f f8 4d 39 ee 0f 82 29 09 00 00 <48> 89 d8 48 c1 e8 03 42 0f b6 04 20 84 c0 0f 85 75 08 00 00 0f b6
RSP: 0018:ffffc900039ff6a0 EFLAGS: 00000216
RAX: ffffffff8937e0ce RBX: ffff888061120889 RCX: ffff88802a830000
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000013
RBP: ffffc900039ff848 R08: ffffffff8100460f R09: 0000000000000003
R10: 0000000094940420 R11: 0000000017171071 R12: dffffc0000000000
R13: 0000000000000004 R14: 0000000000000013 R15: 0000000000000002
FS: 0000000000000000(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc76ea07a60 CR3: 000000005be9c000 CR4: 00000000003526e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
ieee802_11_parse_elems net/mac80211/ieee80211_i.h:2243 [inline]
ieee80211_bss_info_update+0x75d/0xaa0 net/mac80211/scan.c:212
ieee80211_rx_bss_info net/mac80211/ibss.c:1123 [inline]
ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1614 [inline]
ieee80211_ibss_rx_queued_mgmt+0x16d0/0x29c0 net/mac80211/ibss.c:1643
ieee80211_iface_process_skb net/mac80211/iface.c:1459 [inline]
ieee80211_iface_work+0x70e/0xc60 net/mac80211/iface.c:1513
process_one_work+0x863/0x1000 kernel/workqueue.c:2310
worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>


---
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If the report is already addressed, let syzbot know by replying with:
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If you want to overwrite report's subsystems, reply with:
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If the report is a duplicate of another one, reply with:
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If you want to undo deduplication, reply with:
#syz undup

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 50cbba13faa2 Linux 6.1.159
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17062bb4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6a5cbd268406bf43
dashboard link: https://syzkaller.appspot.com/bug?extid=793d40929aaafbecd56c

compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=119ea09a580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14862bb4580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/50ceb00b1b39/disk-50cbba13.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ebb8883b9a29/vmlinux-50cbba13.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7edc2a795f03/bzImage-50cbba13.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by: syzbot+793d40...@syzkaller.appspotmail.com

INFO: task syz.4.21:4532 blocked for more than 143 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:syz.4.21 state:D stack:26688 pid:4532 ppid:4405 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5244 [inline]
__schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
schedule+0xb9/0x180 kernel/sched/core.c:6637
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6696
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x555/0xaf0 kernel/locking/mutex.c:747

comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
chrdev_open+0x597/0x670 fs/char_dev.c:414

do_dentry_open+0x7e9/0x10d0 fs/open.c:882
do_open fs/namei.c:3634 [inline]
path_openat+0x25c6/0x2e70 fs/namei.c:3791
do_filp_open+0x1c1/0x3c0 fs/namei.c:3818
do_sys_openat2+0x142/0x490 fs/open.c:1320
do_sys_open fs/open.c:1336 [inline]
__do_sys_openat fs/open.c:1352 [inline]
__se_sys_openat fs/open.c:1347 [inline]
__x64_sys_openat+0x135/0x160 fs/open.c:1347
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f81fd18f749
RSP: 002b:00007ffd401a6c18 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f81fd3e5fa0 RCX: 00007f81fd18f749

RDX: 0000000000000400 RSI: 0000200000000080 RDI: ffffffffffffff9c

RBP: 00007f81fd213f91 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007f81fd3e5fa0 R14: 00007f81fd3e5fa0 R15: 0000000000000004
</TASK>
INFO: task syz.0.17:4535 blocked for more than 143 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:syz.0.17 state:D stack:26688 pid:4535 ppid:4395 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5244 [inline]
__schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
schedule+0xb9/0x180 kernel/sched/core.c:6637
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6696
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x555/0xaf0 kernel/locking/mutex.c:747

comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
chrdev_open+0x597/0x670 fs/char_dev.c:414

do_dentry_open+0x7e9/0x10d0 fs/open.c:882
do_open fs/namei.c:3634 [inline]
path_openat+0x25c6/0x2e70 fs/namei.c:3791
do_filp_open+0x1c1/0x3c0 fs/namei.c:3818
do_sys_openat2+0x142/0x490 fs/open.c:1320
do_sys_open fs/open.c:1336 [inline]
__do_sys_openat fs/open.c:1352 [inline]
__se_sys_openat fs/open.c:1347 [inline]
__x64_sys_openat+0x135/0x160 fs/open.c:1347
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f3cc038f749
RSP: 002b:00007ffd5918f538 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f3cc05e5fa0 RCX: 00007f3cc038f749

RDX: 0000000000000400 RSI: 0000200000000080 RDI: ffffffffffffff9c

RBP: 00007f3cc0413f91 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007f3cc05e5fa0 R14: 00007f3cc05e5fa0 R15: 0000000000000004
</TASK>
INFO: task syz.2.19:4540 blocked for more than 144 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:syz.2.19 state:D stack:26688 pid:4540 ppid:4408 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5244 [inline]
__schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
schedule+0xb9/0x180 kernel/sched/core.c:6637
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6696
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x555/0xaf0 kernel/locking/mutex.c:747

comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
chrdev_open+0x597/0x670 fs/char_dev.c:414

do_dentry_open+0x7e9/0x10d0 fs/open.c:882
do_open fs/namei.c:3634 [inline]
path_openat+0x25c6/0x2e70 fs/namei.c:3791
do_filp_open+0x1c1/0x3c0 fs/namei.c:3818
do_sys_openat2+0x142/0x490 fs/open.c:1320
do_sys_open fs/open.c:1336 [inline]
__do_sys_openat fs/open.c:1352 [inline]
__se_sys_openat fs/open.c:1347 [inline]
__x64_sys_openat+0x135/0x160 fs/open.c:1347
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f623b78f749
RSP: 002b:00007ffdca7de6a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f623b9e5fa0 RCX: 00007f623b78f749

RDX: 0000000000000400 RSI: 0000200000000080 RDI: ffffffffffffff9c

RBP: 00007f623b813f91 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007f623b9e5fa0 R14: 00007f623b9e5fa0 R15: 0000000000000004
</TASK>
INFO: task syz.3.20:4541 blocked for more than 144 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:syz.3.20 state:D stack:26688 pid:4541 ppid:4404 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5244 [inline]
__schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
schedule+0xb9/0x180 kernel/sched/core.c:6637
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6696
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x555/0xaf0 kernel/locking/mutex.c:747

comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
chrdev_open+0x597/0x670 fs/char_dev.c:414

do_dentry_open+0x7e9/0x10d0 fs/open.c:882
do_open fs/namei.c:3634 [inline]
path_openat+0x25c6/0x2e70 fs/namei.c:3791
do_filp_open+0x1c1/0x3c0 fs/namei.c:3818
do_sys_openat2+0x142/0x490 fs/open.c:1320
do_sys_open fs/open.c:1336 [inline]
__do_sys_openat fs/open.c:1352 [inline]
__se_sys_openat fs/open.c:1347 [inline]
__x64_sys_openat+0x135/0x160 fs/open.c:1347
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fce27d8f749
RSP: 002b:00007ffc09d11cf8 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fce27fe5fa0 RCX: 00007fce27d8f749

RDX: 0000000000000400 RSI: 0000200000000080 RDI: ffffffffffffff9c

RBP: 00007fce27e13f91 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007fce27fe5fa0 R14: 00007fce27fe5fa0 R15: 0000000000000004
</TASK>
INFO: task syz.5.22:4584 blocked for more than 145 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:syz.5.22 state:D stack:26688 pid:4584 ppid:4543 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5244 [inline]
__schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
schedule+0xb9/0x180 kernel/sched/core.c:6637
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6696
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x555/0xaf0 kernel/locking/mutex.c:747

comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
chrdev_open+0x597/0x670 fs/char_dev.c:414

do_dentry_open+0x7e9/0x10d0 fs/open.c:882
do_open fs/namei.c:3634 [inline]
path_openat+0x25c6/0x2e70 fs/namei.c:3791
do_filp_open+0x1c1/0x3c0 fs/namei.c:3818
do_sys_openat2+0x142/0x490 fs/open.c:1320
do_sys_open fs/open.c:1336 [inline]
__do_sys_openat fs/open.c:1352 [inline]
__se_sys_openat fs/open.c:1347 [inline]
__x64_sys_openat+0x135/0x160 fs/open.c:1347
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f203938f749
RSP: 002b:00007ffe37599a18 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f20395e5fa0 RCX: 00007f203938f749

RDX: 0000000000000400 RSI: 0000200000000080 RDI: ffffffffffffff9c

RBP: 00007f2039413f91 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007f20395e5fa0 R14: 00007f20395e5fa0 R15: 0000000000000004

</TASK>

Showing all locks held in the system:

1 lock held by rcu_tasks_kthre/12:
#0: ffffffff8c92bab0 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xf00 kernel/rcu/tasks.h:517
1 lock held by rcu_tasks_trace/13:
#0: ffffffff8c92c2d0 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xf00 kernel/rcu/tasks.h:517
1 lock held by khungtaskd/28:
#0: ffffffff8c92b120 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
#0: ffffffff8c92b120 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
#0: ffffffff8c92b120 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6513
2 locks held by udevd/3636:
#0: ffff8880b8e3aad8 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x26/0x140 kernel/sched/core.c:537
#1: ffff8880b8e27848
(&per_cpu_ptr(group->pcpu, cpu)->seq){-.-.}-{0:0}, at: psi_task_switch+0x398/0x6d0 kernel/sched/psi.c:999
2 locks held by getty/4024:
#0: ffff88802fe7f098 (&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+0x41b/0x1380 drivers/tty/n_tty.c:2198
2 locks held by kworker/u4:5/4366:
#0: ffff888017479138 ((wq_completion)events_unbound){+.+.}-{0:0}
, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
#1: ffffc90002e87d00 ((work_completion)(&sub_info->work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
3 locks held by kworker/u4:7/4461:
2 locks held by syz.1.18/4523:
1 lock held by syz.4.21/4532:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.0.17/4535:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.2.19/4540:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.3.20/4541:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.5.22/4584:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.6.23/4659:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.7.24/4668:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.8.25/4673:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.9.26/4676:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.1.27/4691:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.4.28/4760:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.0.29/4795:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.3.31/4810:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.2.30/4811:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.5.32/4812:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.6.33/4846:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.7.34/4888:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.8.35/4943:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.1.37/4950:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.9.36/4951:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.4.38/4977:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.0.39/4987:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.2.40/5079:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.3.41/5080:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.5.42/5093:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.6.43/5111:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
1 lock held by syz.7.44/5112:
#0: ffff88814cade8f8 (&dev->mutex#3){+.+.}-{3:3}, at: comedi_open+0xbc/0x580 drivers/comedi/comedi_fops.c:2811
2 locks held by syz-executor/5114:
#0: ffffffff8db3b3a8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
#0: ffffffff8db3b3a8 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x740/0xed0 net/core/rtnetlink.c:6147
#1: ffffffff8c930df8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:291 [inline]
#1: ffffffff8c930df8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x455/0x830 kernel/rcu/tree_exp.h:962
1 lock held by syz-executor/5119:
#0: ffffffff8db3b3a8 (rtnl_mutex){+.+.}-{3:3}, at: __tun_chr_ioctl+0x3ab/0x1e10 drivers/net/tun.c:3104

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

NMI backtrace for cpu 1
CPU: 1 PID: 28 Comm: khungtaskd Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
<TASK>

dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106
nmi_cpu_backtrace+0x3f4/0x470 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+0xeee/0xf30 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>
Sending NMI from CPU 1 to CPUs 0:

NMI backtrace for cpu 0

CPU: 0 PID: 46 Comm: kworker/u4:3 Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025

Workqueue: phy17 ieee80211_iface_work
RIP: 0010:hlock_class kernel/locking/lockdep.c:228 [inline]
RIP: 0010:lookup_chain_cache_add kernel/locking/lockdep.c:3737 [inline]
RIP: 0010:validate_chain kernel/locking/lockdep.c:3793 [inline]
RIP: 0010:__lock_acquire+0x13d2/0x7c50 kernel/locking/lockdep.c:5049
Code: e8 03 25 f8 03 00 00 48 8d b8 40 82 8c 90 be 08 00 00 00 e8 90 f7 6d 00 49 b8 00 00 00 00 00 fc ff df 48 0f a3 1d 0e 67 29 0f <72> 25 48 c7 c0 40 f1 9c 96 48 c1 e8 03 42 0f b6 04 00 84 c0 0f 85
RSP: 0018:ffffc90000b778a0 EFLAGS: 00000057
RAX: 0000000000000001 RBX: 0000000000000785 RCX: ffffffff81631b20
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff908c8330
RBP: ffffc90000b77af0 R08: dffffc0000000000 R09: fffffbfff2119067
R10: fffffbfff2119067 R11: 1ffffffff2119066 R12: a80c8f3debaf2941
R13: 0000000057483bae R14: a80c8f3debaf2941 R15: ffff88801cecc650
FS: 0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00007fb983517d60 CR3: 000000000c68e000 CR4: 00000000003506f0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>

lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
process_one_work+0x7d9/0x1160 kernel/workqueue.c:2268
worker_thread+0xaa2/0x1250 kernel/workqueue.c:2439
kthread+0x29d/0x330 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

</TASK>


---
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