INFO: task syz.2.688:9591 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.2.688 state:D stack:26872 pid:9591 tgid:9591 ppid:5823 task_flags:0x400040 flags:0x00080002 Call Trace: context_switch kernel/sched/core.c:5298 [inline] __schedule+0xfee/0x6120 kernel/sched/core.c:6911 __schedule_loop kernel/sched/core.c:6993 [inline] schedule+0xdd/0x390 kernel/sched/core.c:7008 schedule_timeout+0x1b2/0x280 kernel/time/sleep_timeout.c:75 do_wait_for_common kernel/sched/completion.c:100 [inline] __wait_for_common+0x2e7/0x4c0 kernel/sched/completion.c:121 __flush_work+0x7c7/0xcb0 kernel/workqueue.c:4328 vkms_atomic_commit_tail+0x172/0x240 drivers/gpu/drm/vkms/vkms_drv.c:87 commit_tail+0x293/0x430 drivers/gpu/drm/drm_atomic_helper.c:2072 drm_atomic_helper_commit+0x303/0x380 drivers/gpu/drm/drm_atomic_helper.c:2312 drm_atomic_commit+0x230/0x300 drivers/gpu/drm/drm_atomic.c:1775 drm_client_modeset_commit_atomic+0x6a6/0x7e0 drivers/gpu/drm/drm_client_modeset.c:1104 drm_client_modeset_commit_locked+0x14d/0x580 drivers/gpu/drm/drm_client_modeset.c:1207 drm_client_modeset_commit+0x4f/0x80 drivers/gpu/drm/drm_client_modeset.c:1233 __drm_fb_helper_restore_fbdev_mode_unlocked.part.0+0x137/0x160 drivers/gpu/drm/drm_fb_helper.c:137 __drm_fb_helper_restore_fbdev_mode_unlocked drivers/gpu/drm/drm_fb_helper.c:125 [inline] drm_fb_helper_restore_fbdev_mode_unlocked+0x93/0xc0 drivers/gpu/drm/drm_fb_helper.c:168 drm_fbdev_client_restore+0x1b/0x30 drivers/gpu/drm/clients/drm_fbdev_client.c:45 drm_client_dev_restore+0x205/0x2a0 drivers/gpu/drm/drm_client_event.c:118 drm_lastclose drivers/gpu/drm/drm_file.c:411 [inline] drm_release+0x2c6/0x360 drivers/gpu/drm/drm_file.c:444 __fput+0x3ff/0xb40 fs/file_table.c:469 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:67 [inline] exit_to_user_mode_loop+0x100/0x4a0 kernel/entry/common.c:98 __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 include/linux/entry-common.h:325 [inline] do_syscall_64+0x668/0xf80 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7ff925b9c819 RSP: 002b:00007ffeef06b0b8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 RAX: 0000000000000000 RBX: 00007ff925e17da0 RCX: 00007ff925b9c819 RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 RBP: 00007ff925e17da0 R08: 0000000000000006 R09: 0000000000000000 R10: 00000000003c63a4 R11: 0000000000000246 R12: 000000000004488c R13: 00007ff925e1609c R14: 000000000004462d R15: 00007ff925e16090 Showing all locks held in the system: 3 locks held by kworker/0:1/10: #0: ffff88813fe63148 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x1310/0x19a0 kernel/workqueue.c:3251 #1: ffffc900000f7d08 ((work_completion)(&data->fib_event_work)){+.+.}-{0:0}, at: process_one_work+0x988/0x19a0 kernel/workqueue.c:3252 #2: ffff888032ddb240 (&data->fib_lock){+.+.}-{4:4}, at: nsim_fib_event_work+0x1b8/0x63b0 drivers/net/netdevsim/fib.c:1490 1 lock held by khungtaskd/31: #0: ffffffff8e7e7760 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline] #0: ffffffff8e7e7760 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline] #0: ffffffff8e7e7760 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x3d/0x184 kernel/locking/lockdep.c:6775 2 locks held by getty/5585: #0: ffff88803538b0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243 #1: ffffc9000332b2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x419/0x1500 drivers/tty/n_tty.c:2211 3 locks held by kworker/0:4/5905: #0: ffff88813fe63148 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x1310/0x19a0 kernel/workqueue.c:3251 #1: ffffc90004777d08 ((work_completion)(&data->fib_event_work)){+.+.}-{0:0}, at: process_one_work+0x988/0x19a0 kernel/workqueue.c:3252 #2: ffff888047c2a240 (&data->fib_lock){+.+.}-{4:4}, at: nsim_fib_event_work+0x1b8/0x63b0 drivers/net/netdevsim/fib.c:1490 2 locks held by kworker/u10:4/9467: #0: ffff88801cb9e948 ((wq_completion)iou_exit){+.+.}-{0:0}, at: process_one_work+0x1310/0x19a0 kernel/workqueue.c:3251 #1: ffffc90000b87d08 ((work_completion)(&ctx->exit_work)){+.+.}-{0:0}, at: process_one_work+0x988/0x19a0 kernel/workqueue.c:3252 6 locks held by syz.2.688/9591: #0: ffff8880267d8278 (&dev->clientlist_mutex){+.+.}-{4:4}, at: drm_client_dev_restore+0xe9/0x2a0 drivers/gpu/drm/drm_client_event.c:113 #1: ffff8880266e0280 (&helper->lock){+.+.}-{4:4}, at: __drm_fb_helper_restore_fbdev_mode_unlocked.part.0+0x21/0x160 drivers/gpu/drm/drm_fb_helper.c:128 #2: ffff8880267d8130 (&dev->master_mutex){+.+.}-{4:4}, at: drm_master_internal_acquire+0x21/0x80 drivers/gpu/drm/drm_auth.c:435 #3: ffff8880266e0098 (&client->modeset_mutex){+.+.}-{4:4}, at: drm_client_modeset_commit_locked+0x4c/0x580 drivers/gpu/drm/drm_client_modeset.c:1205 #4: ffffc900102d7b30 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_client_modeset_commit_atomic+0xc4/0x7e0 drivers/gpu/drm/drm_client_modeset.c:1043 #5: ffffc900102d7b58 (crtc_ww_class_mutex){+.+.}-{4:4}, at: drm_client_modeset_commit_atomic+0xc4/0x7e0 drivers/gpu/drm/drm_client_modeset.c:1043 2 locks held by kworker/u10:7/10066: #0: ffff88801cb9e948 ((wq_completion)iou_exit){+.+.}-{0:0}, at: process_one_work+0x1310/0x19a0 kernel/workqueue.c:3251 #1: ffffc90004b07d08 ((work_completion)(&ctx->exit_work)){+.+.}-{0:0}, at: process_one_work+0x988/0x19a0 kernel/workqueue.c:3252 2 locks held by syz.4.791/10125: #0: ffffffff8e7d3cc0 (console_lock){+.+.}-{0:0}, at: class_console_lock_constructor include/linux/console.h:736 [inline] #0: ffffffff8e7d3cc0 (console_lock){+.+.}-{0:0}, at: vt_resizex drivers/tty/vt/vt_ioctl.c:700 [inline] #0: ffffffff8e7d3cc0 (console_lock){+.+.}-{0:0}, at: vt_ioctl+0x2657/0x31a0 drivers/tty/vt/vt_ioctl.c:923 #1: ffff8880266e0280 (&helper->lock){+.+.}-{4:4}, at: __drm_fb_helper_restore_fbdev_mode_unlocked.part.0+0x21/0x160 drivers/gpu/drm/drm_fb_helper.c:128 2 locks held by syz.5.810/10275: #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x539/0xfa0 drivers/tty/tty_io.c:2120 #1: ffff8880601ac1c0 (&tty->legacy_mutex){+.+.}-{4:4}, at: tty_init_dev.part.0+0x39/0x470 drivers/tty/tty_io.c:1406 1 lock held by syz.5.810/10276: #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x539/0xfa0 drivers/tty/tty_io.c:2120 1 lock held by syz.1.811/10281: #0: ffff8880267d8130 (&dev->master_mutex){+.+.}-{4:4}, at: class_mutex_constructor include/linux/mutex.h:253 [inline] #0: ffff8880267d8130 (&dev->master_mutex){+.+.}-{4:4}, at: drm_master_open+0x78/0x220 drivers/gpu/drm/drm_auth.c:325 1 lock held by syz.6.812/10371: #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x539/0xfa0 drivers/tty/tty_io.c:2120 1 lock held by syz.8.829/10526: #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x539/0xfa0 drivers/tty/tty_io.c:2120 1 lock held by syz.8.829/10527: #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x539/0xfa0 drivers/tty/tty_io.c:2120 1 lock held by syz.0.841/10794: #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x539/0xfa0 drivers/tty/tty_io.c:2120 1 lock held by syz.4.846/10847: #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x539/0xfa0 drivers/tty/tty_io.c:2120 1 lock held by syz.3.847/10878: #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: class_mutex_constructor include/linux/mutex.h:253 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: ptmx_open drivers/tty/pty.c:798 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: ptmx_open+0x150/0x3c0 drivers/tty/pty.c:765 1 lock held by syz.5.848/10909: #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x539/0xfa0 drivers/tty/tty_io.c:2120 1 lock held by syz.1.850/10941: #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x539/0xfa0 drivers/tty/tty_io.c:2120 1 lock held by syz.7.862/11043: #0: ffff8880267d8130 (&dev->master_mutex){+.+.}-{4:4}, at: class_mutex_constructor include/linux/mutex.h:253 [inline] #0: ffff8880267d8130 (&dev->master_mutex){+.+.}-{4:4}, at: drm_master_open+0x78/0x220 drivers/gpu/drm/drm_auth.c:325 1 lock held by syz.6.863/11050: #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x539/0xfa0 drivers/tty/tty_io.c:2120 1 lock held by syz.9.865/11083: #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x539/0xfa0 drivers/tty/tty_io.c:2120 1 lock held by syz.8.867/11118: #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x539/0xfa0 drivers/tty/tty_io.c:2120 1 lock held by syz.0.877/11203: #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x539/0xfa0 drivers/tty/tty_io.c:2120 1 lock held by syz.2.881/11230: #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x539/0xfa0 drivers/tty/tty_io.c:2120 1 lock held by syz.4.883/11279: #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x539/0xfa0 drivers/tty/tty_io.c:2120 1 lock held by syz.3.885/11286: #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x539/0xfa0 drivers/tty/tty_io.c:2120 1 lock held by syz.3.885/11287: #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x539/0xfa0 drivers/tty/tty_io.c:2120 1 lock held by syz.5.888/11332: #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open_by_driver drivers/tty/tty_io.c:2037 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: tty_open+0x539/0xfa0 drivers/tty/tty_io.c:2120 1 lock held by syz.1.891/11364: #0: ffff8880267d8130 (&dev->master_mutex){+.+.}-{4:4}, at: class_mutex_constructor include/linux/mutex.h:253 [inline] #0: ffff8880267d8130 (&dev->master_mutex){+.+.}-{4:4}, at: drm_master_open+0x78/0x220 drivers/gpu/drm/drm_auth.c:325 2 locks held by syz-executor/11373: 1 lock held by syz.6.894/11408: #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: class_mutex_constructor include/linux/mutex.h:253 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: ptmx_open drivers/tty/pty.c:798 [inline] #0: ffffffff8f4f14a8 (tty_mutex){+.+.}-{4:4}, at: ptmx_open+0x150/0x3c0 drivers/tty/pty.c:765 ============================================= NMI backtrace for cpu 0 CPU: 0 UID: 0 PID: 31 Comm: khungtaskd Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026 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+0x754/0xd80 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245