INFO: task syz.2.2213:18197 blocked for more than 143 seconds. Tainted: G U L syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz.2.2213 state:D stack:26016 pid:18197 tgid:18186 ppid:16665 task_flags:0x400040 flags:0x00080002 Call Trace: context_switch kernel/sched/core.c:5256 [inline] __schedule+0x1139/0x6150 kernel/sched/core.c:6863 __schedule_loop kernel/sched/core.c:6945 [inline] schedule+0xe7/0x3a0 kernel/sched/core.c:6960 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7017 __mutex_lock_common kernel/locking/mutex.c:692 [inline] __mutex_lock+0xc69/0x1ca0 kernel/locking/mutex.c:776 tty_release_struct+0xad/0xe0 drivers/tty/tty_io.c:1691 tty_release+0xe2d/0x1470 drivers/tty/tty_io.c:1852 __fput+0x402/0xb70 fs/file_table.c:468 task_work_run+0x150/0x240 kernel/task_work.c:233 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] __exit_to_user_mode_loop kernel/entry/common.c:44 [inline] exit_to_user_mode_loop+0xfb/0x540 kernel/entry/common.c:75 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline] syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline] syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline] do_syscall_64+0x4ee/0xf80 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f5f1218f7c9 RSP: 002b:00007f5f103d5038 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 RAX: 0000000000000000 RBX: 00007f5f123e6090 RCX: 00007f5f1218f7c9 RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000002 RBP: 00007f5f12213f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f5f123e6128 R14: 00007f5f123e6090 R15: 00007ffc1eeef008 INFO: task syz.0.2219:18223 blocked for more than 143 seconds. Tainted: G U L syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz.0.2219 state:D stack:28808 pid:18223 tgid:18218 ppid:16812 task_flags:0x400040 flags:0x00080002 Call Trace: context_switch kernel/sched/core.c:5256 [inline] __schedule+0x1139/0x6150 kernel/sched/core.c:6863 __schedule_loop kernel/sched/core.c:6945 [inline] schedule+0xe7/0x3a0 kernel/sched/core.c:6960 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7017 __mutex_lock_common kernel/locking/mutex.c:692 [inline] __mutex_lock+0xc69/0x1ca0 kernel/locking/mutex.c:776 tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] tty_open+0x53d/0xf90 drivers/tty/tty_io.c:2120 chrdev_open+0x234/0x6a0 fs/char_dev.c:414 do_dentry_open+0x748/0x1590 fs/open.c:962 vfs_open+0x82/0x3f0 fs/open.c:1094 do_open fs/namei.c:4628 [inline] path_openat+0x2078/0x3140 fs/namei.c:4787 do_filp_open+0x20b/0x470 fs/namei.c:4814 do_sys_openat2+0x121/0x290 fs/open.c:1430 do_sys_open fs/open.c:1436 [inline] __do_sys_openat fs/open.c:1452 [inline] __se_sys_openat fs/open.c:1447 [inline] __x64_sys_openat+0x174/0x210 fs/open.c:1447 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f71c578f7c9 RSP: 002b:00007f71c65e0038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 00007f71c59e6090 RCX: 00007f71c578f7c9 RDX: 0000000000101840 RSI: 0000200000000080 RDI: ffffffffffffff9c RBP: 00007f71c5813f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f71c59e6128 R14: 00007f71c59e6090 R15: 00007ffe0ca771a8 INFO: task syz.3.2220:18233 blocked for more than 143 seconds. Tainted: G U L syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz.3.2220 state:D stack:26720 pid:18233 tgid:18230 ppid:17272 task_flags:0x400040 flags:0x00080002 Call Trace: context_switch kernel/sched/core.c:5256 [inline] __schedule+0x1139/0x6150 kernel/sched/core.c:6863 __schedule_loop kernel/sched/core.c:6945 [inline] schedule+0xe7/0x3a0 kernel/sched/core.c:6960 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7017 __mutex_lock_common kernel/locking/mutex.c:692 [inline] __mutex_lock+0xc69/0x1ca0 kernel/locking/mutex.c:776 tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] tty_open+0x53d/0xf90 drivers/tty/tty_io.c:2120 chrdev_open+0x234/0x6a0 fs/char_dev.c:414 do_dentry_open+0x748/0x1590 fs/open.c:962 vfs_open+0x82/0x3f0 fs/open.c:1094 do_open fs/namei.c:4628 [inline] path_openat+0x2078/0x3140 fs/namei.c:4787 do_filp_open+0x20b/0x470 fs/namei.c:4814 do_sys_openat2+0x121/0x290 fs/open.c:1430 do_sys_open fs/open.c:1436 [inline] __do_sys_openat fs/open.c:1452 [inline] __se_sys_openat fs/open.c:1447 [inline] __x64_sys_openat+0x174/0x210 fs/open.c:1447 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f19df58f7c9 RSP: 002b:00007f19e04ec038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 00007f19df7e6090 RCX: 00007f19df58f7c9 RDX: 0000000000000201 RSI: 0000200000000540 RDI: ffffffffffffff9c RBP: 00007f19df613f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f19df7e6128 R14: 00007f19df7e6090 R15: 00007ffe695071c8 Showing all locks held in the system: 1 lock held by khungtaskd/31: #0: ffffffff8e3c9520 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #0: ffffffff8e3c9520 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #0: ffffffff8e3c9520 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x36/0x1c0 kernel/locking/lockdep.c:6775 1 lock held by syz.2.186/6828: 1 lock held by syz.9.1985/16513: 2 locks held by getty/16850: #0: ffff88814e4150a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243 #1: ffffc900048832f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x41b/0x1510 drivers/tty/n_tty.c:2211 3 locks held by kworker/u8:6/17687: #0: ffff888030a90148 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x128d/0x1b20 kernel/workqueue.c:3232 #1: ffffc90003657c90 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work+0x914/0x1b20 kernel/workqueue.c:3233 #2: ffffffff90145068 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline] #2: ffffffff90145068 (rtnl_mutex){+.+.}-{4:4}, at: addrconf_dad_work+0x120/0x14f0 net/ipv6/addrconf.c:4194 1 lock held by syz.2.2213/18197: #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_release_struct+0xad/0xe0 drivers/tty/tty_io.c:1691 4 locks held by syz.2.2213/18205: 1 lock held by syz.0.2219/18223: #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x53d/0xf90 drivers/tty/tty_io.c:2120 1 lock held by syz.3.2220/18233: #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x53d/0xf90 drivers/tty/tty_io.c:2120 1 lock held by syz.1.2223/18299: #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x53d/0xf90 drivers/tty/tty_io.c:2120 1 lock held by syz.7.2231/18639: #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x53d/0xf90 drivers/tty/tty_io.c:2120 1 lock held by syz.9.2232/18657: #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x53d/0xf90 drivers/tty/tty_io.c:2120 1 lock held by syz.8.2238/18696: #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x53d/0xf90 drivers/tty/tty_io.c:2120 1 lock held by syz.6.2243/18759: #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x53d/0xf90 drivers/tty/tty_io.c:2120 1 lock held by syz.6.2243/18761: #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x53d/0xf90 drivers/tty/tty_io.c:2120 1 lock held by syz.4.2249/19043: #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x53d/0xf90 drivers/tty/tty_io.c:2120 1 lock held by syz.2.2246/19056: #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x53d/0xf90 drivers/tty/tty_io.c:2120 1 lock held by syz.5.2252/19070: #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x53d/0xf90 drivers/tty/tty_io.c:2120 1 lock held by syz.3.2247/19090: #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x53d/0xf90 drivers/tty/tty_io.c:2120 1 lock held by syz.0.2253/19308: #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x53d/0xf90 drivers/tty/tty_io.c:2120 1 lock held by syz.1.2258/19338: #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x53d/0xf90 drivers/tty/tty_io.c:2120 1 lock held by syz.9.2261/19388: #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x53d/0xf90 drivers/tty/tty_io.c:2120 1 lock held by syz-executor/19434: #0: ffffffff90145068 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline] #0: ffffffff90145068 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline] #0: ffffffff90145068 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0x5f6/0x1f50 net/core/rtnetlink.c:4071 1 lock held by syz.7.2268/19459: #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f071b48 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x53d/0xf90 drivers/tty/tty_io.c:2120 2 locks held by syz-executor/19470: 1 lock held by dhcpcd-run-hook/19482: ============================================= NMI backtrace for cpu 0 CPU: 0 UID: 0 PID: 31 Comm: khungtaskd Tainted: G U L syzkaller #0 PREEMPT(full) Tainted: [U]=USER, [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 nmi_cpu_backtrace+0x27b/0x390 lib/nmi_backtrace.c:113 nmi_trigger_cpumask_backtrace+0x29c/0x300 lib/nmi_backtrace.c:62 trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline] __sys_info lib/sys_info.c:157 [inline] sys_info+0x133/0x180 lib/sys_info.c:165 check_hung_uninterruptible_tasks kernel/hung_task.c:346 [inline] watchdog+0xe66/0x1180 kernel/hung_task.c:515 kthread+0x3c5/0x780 kernel/kthread.c:463 ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246