INFO: task udevd:2854 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:R running task stack:23752 pid:2854 tgid:2854 ppid:1 task_flags:0x400140 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5298 [inline] __schedule+0xeb1/0x4220 kernel/sched/core.c:6911 __schedule_loop kernel/sched/core.c:6993 [inline] schedule+0xdd/0x390 kernel/sched/core.c:7008 schedule_hrtimeout_range_clock+0x21b/0x320 kernel/time/sleep_timeout.c:216 ep_poll fs/eventpoll.c:2028 [inline] do_epoll_wait+0xdc3/0x1020 fs/eventpoll.c:2462 __do_sys_epoll_wait fs/eventpoll.c:2470 [inline] __se_sys_epoll_wait fs/eventpoll.c:2465 [inline] __x64_sys_epoll_wait+0x194/0x290 fs/eventpoll.c:2465 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x106/0x7b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f402a1c0407 RSP: 002b:00007fffaa855e20 EFLAGS: 00000202 ORIG_RAX: 00000000000000e8 RAX: ffffffffffffffda RBX: 00007f402a0d2880 RCX: 00007f402a1c0407 RDX: 0000000000000008 RSI: 00007fffaa855f80 RDI: 000000000000000b RBP: 00005650e86312a0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000bb8 R11: 0000000000000202 R12: 0000000000000000 R13: 00005650ca54b100 R14: 0000000000000000 R15: 0000000000000000 Showing all locks held in the system: 1 lock held by khungtaskd/29: #0: ffffffff896de6e0 ( rcu_read_lock ){....}-{1:3} , at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline] , at: rcu_read_lock include/linux/rcupdate.h:850 [inline] , at: debug_show_all_locks+0x3d/0x184 kernel/locking/lockdep.c:6775 7 locks held by kworker/1:1/36: 4 locks held by kworker/u8:3/43: #0: ffff888101299148 ( (wq_completion)netns ){+.+.}-{0:0} , at: process_one_work+0x1310/0x19a0 kernel/workqueue.c:3251 #1: ffffc900004e7d18 ( net_cleanup_work ){+.+.}-{0:0} , at: process_one_work+0x988/0x19a0 kernel/workqueue.c:3252 #2: ffffffff8aae1bf0 ( pernet_ops_rwsem ){++++}-{4:4} , at: cleanup_net+0xb8/0x9e0 net/core/net_namespace.c:675 #3: ffffffff8aafa128 ( rtnl_mutex ){+.+.}-{4:4} , at: ops_exit_rtnl_list net/core/net_namespace.c:173 [inline] , at: ops_undo_list+0x7ec/0xab0 net/core/net_namespace.c:248 3 locks held by kworker/0:2/352: #0: ffff88810006b148 ( (wq_completion)events ){+.+.}-{0:0} , at: process_one_work+0x1310/0x19a0 kernel/workqueue.c:3251 #1: ffffc9000182fd18 ( free_ipc_work ){+.+.}-{0:0} , at: process_one_work+0x988/0x19a0 kernel/workqueue.c:3252 #2: ffffffff896ea2f8 ( rcu_state.exp_mutex ){+.+.}-{4:4} , at: exp_funnel_lock+0x19e/0x3c0 kernel/rcu/tree_exp.h:343 5 locks held by kworker/1:2/1119: 2 locks held by acpid/2839: #0: ffff8881228cd118 ( &evdev->mutex ){+.+.}-{4:4} , at: evdev_close_device drivers/input/evdev.c:402 [inline] , at: evdev_release+0x29e/0x420 drivers/input/evdev.c:447 #1: ffff88811c5262c0 ( &dev->mutex #2 ){+.+.}-{4:4} , at: class_mutex_constructor include/linux/mutex.h:253 [inline] , at: input_close_device+0x46/0x2b0 drivers/input/input.c:646 2 locks held by getty/2917: #0: ffff8881127100a0 ( &tty->ldisc_sem ){++++}-{0:0} , at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243 #1: ffffc900000432f0 ( &ldata->atomic_read_lock ){+.+.}-{4:4} , at: n_tty_read+0x419/0x1500 drivers/tty/n_tty.c:2211 2 locks held by udevd/5231: #0: ffff88811aadc118 ( &evdev->mutex ){+.+.}-{4:4} , at: evdev_close_device drivers/input/evdev.c:402 [inline] , at: evdev_release+0x29e/0x420 drivers/input/evdev.c:447 #1: ffff88811aadd2c0 ( &dev->mutex #2 ){+.+.}-{4:4} , at: class_mutex_constructor include/linux/mutex.h:253 [inline] , at: input_close_device+0x46/0x2b0 drivers/input/input.c:646 2 locks held by kworker/1:4/5251: 3 locks held by kworker/1:6/5647: 3 locks held by kworker/1:5/9236: 8 locks held by kworker/1:0/11868: 2 locks held by kworker/1:8/12199: 1 lock held by syz-executor/12254: #0: ffffffff8aafa128 ( rtnl_mutex ){+.+.}-{4:4} , at: rtnl_lock net/core/rtnetlink.c:80 [inline] , at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline] , at: rtnl_newlink+0x8c9/0x2300 net/core/rtnetlink.c:4071 1 lock held by syz-executor/12255: #0: ffffffff8aafa128 ( rtnl_mutex ){+.+.}-{4:4} , at: rtnl_lock net/core/rtnetlink.c:80 [inline] , at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline] , at: rtnl_newlink+0x8c9/0x2300 net/core/rtnetlink.c:4071 1 lock held by syz-executor/13315: #0: ffffffff8aafa128 (rtnl_mutex){+.+.}-{4:4} , at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline] , at: inet_rtm_newaddr+0x30c/0x18b0 net/ipv4/devinet.c:978 1 lock held by syz-executor/13317: #0: ffffffff8aafa128 ( rtnl_mutex ){+.+.}-{4:4} , at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline] , at: inet_rtm_newaddr+0x30c/0x18b0 net/ipv4/devinet.c:978 1 lock held by syz-executor/13321: #0: ffffffff8aafa128 ( rtnl_mutex ){+.+.}-{4:4} , at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline] , at: inet_rtm_newaddr+0x30c/0x18b0 net/ipv4/devinet.c:978 1 lock held by syz-executor/13323: #0: ffffffff8aafa128 ( rtnl_mutex ){+.+.}-{4:4} , at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline] , at: inet_rtm_newaddr+0x30c/0x18b0 net/ipv4/devinet.c:978 1 lock held by syz-executor/13326: #0: ffffffff8aafa128 ( rtnl_mutex ){+.+.}-{4:4} , at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline] , at: inet_rtm_newaddr+0x30c/0x18b0 net/ipv4/devinet.c:978 ============================================= NMI backtrace for cpu 0 CPU: 0 UID: 0 PID: 29 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 Call Trace: __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:161 [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:346 [inline] watchdog+0xd25/0x1050 kernel/hung_task.c:515 kthread+0x370/0x450 kernel/kthread.c:436 ret_from_fork+0x6c3/0xcb0 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 Sending NMI from CPU 0 to CPUs 1: yealink 4-1:36.0: urb_irq_callback - urb status -71 NMI backtrace for cpu 1 CPU: 1 UID: 0 PID: 11868 Comm: kworker/1:0 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 Workqueue: events free_obj_work RIP: 0010:check_kcov_mode kernel/kcov.c:183 [inline] RIP: 0010:__sanitizer_cov_trace_pc+0x17/0x70 kernel/kcov.c:217 Code: 01 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 65 8b 05 05 3b 43 0b 48 8b 34 24 65 48 8b 15 e1 3a 43 0b 00 01 ff 00 74 1b f6 c4 01 74 07 a9 00 00 ff 00 74 05 e9 91 25 RSP: 0018:ffffc900001a8448 EFLAGS: 00000046 RAX: 0000000080000102 RBX: 0000000000000000 RCX: ffffffff8321a79e RDX: ffff888116d50000 RSI: ffffffff83201d67 RDI: ffffffff941b36c0 RBP: ffffffff941b36c0 R08: 0000000000000001 R09: 000000000000000a R10: 0000000000000031 R11: 0000000000000000 R12: 0000000000000003 R13: 0000000000000031 R14: 0000000000000010 R15: ffffffff83201d50 FS: 0000000000000000(0000) GS:ffff8882687ce000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fdadabd1000 CR3: 00000001189c6000 CR4: 00000000003506f0 Call Trace: io_serial_out+0x17/0xb0 drivers/tty/serial/8250/8250_port.c:405 serial_port_out include/linux/serial_core.h:811 [inline] serial8250_console_putchar drivers/tty/serial/8250/8250_port.c:3192 [inline] serial8250_console_fifo_write drivers/tty/serial/8250/8250_port.c:3264 [inline] serial8250_console_write+0xde8/0x1900 drivers/tty/serial/8250/8250_port.c:3342 console_emit_next_record kernel/printk/printk.c:3183 [inline] console_flush_one_record+0x790/0xe50 kernel/printk/printk.c:3269 console_flush_all kernel/printk/printk.c:3343 [inline] __console_flush_and_unlock kernel/printk/printk.c:3373 [inline] console_unlock+0x103/0x260 kernel/printk/printk.c:3413 vprintk_emit+0x407/0x6b0 kernel/printk/printk.c:2479 dev_vprintk_emit+0x394/0x3e0 drivers/base/core.c:4913 dev_printk_emit+0xd2/0x10d drivers/base/core.c:4924 __dev_printk+0xcb/0x100 drivers/base/core.c:4936 _dev_err+0xef/0x127 drivers/base/core.c:4979 urb_irq_callback.cold+0x41/0xfd drivers/input/misc/yealink.c:418 __usb_hcd_giveback_urb+0x38d/0x610 drivers/usb/core/hcd.c:1657 usb_hcd_giveback_urb+0x3ca/0x4a0 drivers/usb/core/hcd.c:1741 dummy_timer+0xd85/0x3670 drivers/usb/gadget/udc/dummy_hcd.c:1995 __run_hrtimer kernel/time/hrtimer.c:1785 [inline] __hrtimer_run_queues+0x50e/0xa70 kernel/time/hrtimer.c:1849 hrtimer_run_softirq+0x17d/0x350 kernel/time/hrtimer.c:1866 handle_softirqs+0x1de/0x9d0 kernel/softirq.c:622 __do_softirq kernel/softirq.c:656 [inline] invoke_softirq kernel/softirq.c:496 [inline] __irq_exit_rcu+0xed/0x150 kernel/softirq.c:723 irq_exit_rcu+0x9/0x30 kernel/softirq.c:739 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline] sysvec_apic_timer_interrupt+0x8f/0xb0 arch/x86/kernel/apic/apic.c:1056 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 RIP: 0010:lock_acquire+0x5e/0x380 kernel/locking/lockdep.c:5872 Code: 05 3b 44 66 0b 83 f8 07 0f 87 f0 00 00 00 48 0f a3 05 c6 20 61 09 0f 82 c2 02 00 00 8b 35 6e 30 61 09 85 f6 0f 85 dd 00 00 00 <48> 8b 44 24 30 65 48 2b 05 dd 43 66 0b 0f 85 02 03 00 00 48 83 c4 RSP: 0018:ffffc90012947690 EFLAGS: 00000206 RAX: 0000000000000046 RBX: 0000000000000000 RCX: 0000000000000002 RDX: 0000000000000000 RSI: ffffffff890010b3 RDI: ffffffff87afc6a0 RBP: ffffffff896de6e0 R08: 000000002d532367 R09: 0000000000000007 R10: 0000000000000200 R11: 0000000000000000 R12: 0000000000000002 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 rcu_lock_acquire include/linux/rcupdate.h:312 [inline] rcu_read_lock include/linux/rcupdate.h:850 [inline] class_rcu_constructor include/linux/rcupdate.h:1193 [inline] unwind_next_frame+0xd1/0x1ea0 arch/x86/kernel/unwind_orc.c:495 arch_stack_walk+0x94/0xf0 arch/x86/kernel/stacktrace.c:25 stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57 kasan_save_track+0x14/0x30 mm/kasan/common.c:78 kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:253 [inline] __kasan_slab_free+0x43/0x70 mm/kasan/common.c:285 kasan_slab_free include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:2685 [inline] slab_free mm/slub.c:6165 [inline] kmem_cache_free+0x105/0x640 mm/slub.c:6295 free_object_list.isra.0+0xf8/0x2a0 lib/debugobjects.c:326 free_obj_work+0x19d/0x3d0 lib/debugobjects.c:530 process_one_work+0xa23/0x19a0 kernel/workqueue.c:3276 process_scheduled_works kernel/workqueue.c:3359 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3440 kthread+0x370/0x450 kernel/kthread.c:436 ret_from_fork+0x6c3/0xcb0 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245