INFO: task udevd:4195 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:udevd           state:D stack:23120 pid: 4195 ppid:  3562 flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11ef/0x43c0 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+0xcfc/0x2400 kernel/locking/mutex.c:669
 __mutex_lock kernel/locking/mutex.c:729 [inline]
 mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
 device_lock include/linux/device.h:809 [inline]
 uevent_show+0x17a/0x330 drivers/base/core.c:2408
 dev_attr_show+0x50/0xb0 drivers/base/core.c:2110
 sysfs_kf_seq_show+0x316/0x4c0 fs/sysfs/file.c:61
 seq_read_iter+0x49b/0xd50 fs/seq_file.c:230
 call_read_iter include/linux/fs.h:2167 [inline]
 new_sync_read fs/read_write.c:404 [inline]
 vfs_read+0x759/0xd60 fs/read_write.c:485
 ksys_read+0x152/0x260 fs/read_write.c:623
 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: 0033:0x7f298df5d407
RSP: 002b:00007ffee2f39660 EFLAGS: 00000202 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f298de6f880 RCX: 00007f298df5d407
RDX: 0000000000001000 RSI: 0000563bfdcc5a00 RDI: 0000000000000008
RBP: 00007f298e0a5ff0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 000000000000000a
R13: 00007f298e0a5ea0 R14: 0000000000000000 R15: 0000563bfdcd0ae0
 </TASK>

Showing all locks held in the system:
6 locks held by kworker/1:1/23:
 #0: ffff88801bd3b138 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x761/0x1010 kernel/workqueue.c:-1
 #1: ffffc90000ddfd00 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x79f/0x1010 kernel/workqueue.c:2285
 #2: ffff888147ed1220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:809 [inline]
 #2: ffff888147ed1220 (&dev->mutex){....}-{3:3}, at: hub_event+0x19f/0x55e0 drivers/usb/core/hub.c:5827
 #3: ffff888061dfb220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:809 [inline]
 #3: ffff888061dfb220 (&dev->mutex){....}-{3:3}, at: __device_attach+0x85/0x480 drivers/base/dd.c:974
 #4: ffff8880618531a8 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:809 [inline]
 #4: ffff8880618531a8 (&dev->mutex){....}-{3:3}, at: __device_attach+0x85/0x480 drivers/base/dd.c:974
 #5: ffffffff8c1cfb90 (umhelper_sem){++++}-{3:3}, at: usermodehelper_read_trylock+0xf4/0x330 kernel/umh.c:217
1 lock held by khungtaskd/27:
 #0: ffffffff8c31f360 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
2 locks held by syslogd/3544:
 #0: ffff8880b903a358 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x26/0x140 kernel/sched/core.c:475
 #1: ffff8880b9027888 (&per_cpu_ptr(group->pcpu, cpu)->seq){-.-.}-{0:0}, at: psi_task_switch+0x4fe/0x7d0 kernel/sched/psi.c:891
2 locks held by udevd/3562:
 #0: ffff8880206b3d18 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_put+0xf9/0x7d0 block/bdev.c:915
 #1: ffff888020923468 (&lo->lo_mutex){+.+.}-{3:3}, at: lo_release+0x4d/0x1f0 drivers/block/loop.c:2071
2 locks held by getty/3948:
 #0: ffff88814c9c4098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
 #1: ffffc900026562e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x5df/0x1a70 drivers/tty/n_tty.c:2158
4 locks held by udevd/4195:
 #0: ffff88801f5189e0 (&p->lock){+.+.}-{3:3}, at: seq_read_iter+0xad/0xd50 fs/seq_file.c:182
 #1: ffff888062891488 (&of->mutex){+.+.}-{3:3}, at: kernfs_seq_start+0x51/0x3c0 fs/kernfs/file.c:112
 #2: ffff8880621b7cb8 (kn->active#32){++++}-{0:0}, at: kernfs_seq_start+0x71/0x3c0 fs/kernfs/file.c:113
 #3: ffff888061dfb220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:809 [inline]
 #3: ffff888061dfb220 (&dev->mutex){....}-{3:3}, at: uevent_show+0x17a/0x330 drivers/base/core.c:2408
1 lock held by udevd/4210:
 #0: ffff8880206b3d18 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev+0x157/0xa60 block/bdev.c:820
5 locks held by kworker/0:17/4737:
 #0: ffff88801bd3b138 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x761/0x1010 kernel/workqueue.c:-1
 #1: ffffc90004177d00 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x79f/0x1010 kernel/workqueue.c:2285
 #2: ffff888024769220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:809 [inline]
 #2: ffff888024769220 (&dev->mutex){....}-{3:3}, at: hub_event+0x19f/0x55e0 drivers/usb/core/hub.c:5827
 #3: ffff88802476c5c8 (&port_dev->status_lock){+.+.}-{3:3}, at: usb_lock_port drivers/usb/core/hub.c:3168 [inline]
 #3: ffff88802476c5c8 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_port_connect drivers/usb/core/hub.c:5393 [inline]
 #3: ffff88802476c5c8 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_port_connect_change drivers/usb/core/hub.c:5637 [inline]
 #3: ffff88802476c5c8 (&port_dev->status_lock){+.+.}-{3:3}, at: port_event drivers/usb/core/hub.c:5799 [inline]
 #3: ffff88802476c5c8 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_event+0x3163/0x55e0 drivers/usb/core/hub.c:5881
 #4: ffff888024111768 (hcd->address0_mutex){+.+.}-{3:3}, at: hub_port_connect drivers/usb/core/hub.c:5394 [inline]
 #4: ffff888024111768 (hcd->address0_mutex){+.+.}-{3:3}, at: hub_port_connect_change drivers/usb/core/hub.c:5637 [inline]
 #4: ffff888024111768 (hcd->address0_mutex){+.+.}-{3:3}, at: port_event drivers/usb/core/hub.c:5799 [inline]
 #4: ffff888024111768 (hcd->address0_mutex){+.+.}-{3:3}, at: hub_event+0x3195/0x55e0 drivers/usb/core/hub.c:5881
2 locks held by syz.4.961/11827:
 #0: ffffffff8c809388 (uuid_mutex){+.+.}-{3:3}, at: btrfs_mount_root+0x271/0x930 fs/btrfs/super.c:1708
 #1: ffff8880206b3d18 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev+0x157/0xa60 block/bdev.c:820

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

NMI backtrace for cpu 1
CPU: 1 PID: 27 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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+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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 9875 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:preempt_count arch/x86/include/asm/preempt.h:27 [inline]
RIP: 0010:check_kcov_mode kernel/kcov.c:172 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0xc/0x60 kernel/kcov.c:206
Code: 89 fb e8 17 00 00 00 48 8b 3d 30 c0 10 0c 48 89 de 5b e9 57 50 44 00 00 00 cc cc 00 00 cc 48 8b 04 24 65 48 8b 0d c4 26 89 7e <65> 8b 15 c5 26 89 7e 81 e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75
RSP: 0018:ffffc9000312feb0 EFLAGS: 00000006
RAX: ffffffff812c2a19 RBX: 0000000000004000 RCX: ffff888021479dc0
RDX: 0000000000000000 RSI: 0000000000004000 RDI: 0000000000000000
RBP: ffffc9000312ff48 R08: ffff888021479dc7 R09: 1ffff1100428f3b8
R10: dffffc0000000000 R11: ffffed100428f3b9 R12: 0000000000000000
R13: dffffc0000000000 R14: ffffc9000312ff58 R15: ffff888021479dc0
FS:  000055558e866500(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f20d32752f8 CR3: 000000005445b000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 switch_fpu_return+0x19/0x1d0 arch/x86/kernel/fpu/core.c:399
 arch_exit_to_user_mode_prepare arch/x86/include/asm/entry-common.h:58 [inline]
 exit_to_user_mode_prepare+0x11d/0x180 kernel/entry/common.c:216
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fbaa6fb268e
Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
RSP: 002b:00007ffca987cd38 EFLAGS: 00000246 ORIG_RAX: 00000000000000e6
RAX: 0000000000000000 RBX: 000055558e866500 RCX: 00007fbaa6fb268e
RDX: 00007ffca987cd90 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007ffca987cdfc R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000001388
R13: 00000000000927c0 R14: 000000000004dd31 R15: 00007ffca987ce50
 </TASK>