syzbot


INFO: task hung in nsim_dev_trap_report_work (2)

Status: upstream: reported on 2025/12/05 08:37
Reported-by: syzbot+fd06e44aa89238f5cd12@syzkaller.appspotmail.com
First crash: 198d, last: 31d
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: task hung in nsim_dev_trap_report_work origin:lts-only 1 syz 84 550d 853d 0/3 auto-obsoleted due to no activity on 2025/02/25 20:54

Sample crash report:
INFO: task kworker/1:8:5663 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/1:8     state:D stack:25944 pid: 5663 ppid:     2 flags:0x00004000
Workqueue: events nsim_dev_trap_report_work

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
 nsim_dev_trap_report_work+0x56/0xb40 drivers/net/netdevsim/dev.c:757
 process_one_work+0x85f/0x1010 kernel/workqueue.c:2310
 worker_thread+0xaa6/0x1290 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
INFO: task syz-executor:13933 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:22488 pid:13933 ppid:     1 flags:0x00004004
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
 rcu_barrier+0xa1/0x4c0 kernel/rcu/tree.c:4043
 netdev_run_todo+0x2fd/0xa70 net/core/dev.c:10688
 nsim_destroy+0xb2/0x150 drivers/net/netdevsim/netdev.c:387
 __nsim_dev_port_del+0x155/0x1c0 drivers/net/netdevsim/dev.c:1349
 nsim_dev_port_del_all drivers/net/netdevsim/dev.c:1362 [inline]
 nsim_dev_reload_destroy+0x16c/0x240 drivers/net/netdevsim/dev.c:1561
 nsim_dev_remove+0x59/0x100 drivers/net/netdevsim/dev.c:1577
 __device_release_driver drivers/base/dd.c:1227 [inline]
 device_release_driver_internal+0x475/0x750 drivers/base/dd.c:1262
 bus_remove_device+0x2e2/0x400 drivers/base/bus.c:531
 device_del+0x6af/0xaf0 drivers/base/core.c:3600
 device_unregister+0x1c/0xc0 drivers/base/core.c:3633
 nsim_bus_dev_del drivers/net/netdevsim/bus.c:454 [inline]
 del_device_store+0x296/0x3a0 drivers/net/netdevsim/bus.c:354
 kernfs_fop_write_iter+0x379/0x4c0 fs/kernfs/file.c:296
 call_write_iter include/linux/fs.h:2173 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x745/0xd60 fs/read_write.c:594
 ksys_write+0x152/0x260 fs/read_write.c:647
 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: 0033:0x7f4decffc68e
RSP: 002b:00007ffd2a41e098 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000055558ef1a500 RCX: 00007f4decffc68e
RDX: 0000000000000001 RSI: 00007ffd2a41e120 RDI: 0000000000000005
RBP: 00007f4ded0d25f2 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffd2a41e120 R14: 00007f4dedde3620 R15: 0000000000000003
 </TASK>
INFO: task syz-executor:14007 blocked for more than 144 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:22512 pid:14007 ppid:     1 flags:0x00004004
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
 del_device_store+0xd3/0x3a0 drivers/net/netdevsim/bus.c:344
 kernfs_fop_write_iter+0x379/0x4c0 fs/kernfs/file.c:296
 call_write_iter include/linux/fs.h:2173 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x745/0xd60 fs/read_write.c:594
 ksys_write+0x152/0x260 fs/read_write.c:647
 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: 0033:0x7f4c33c1e68e
RSP: 002b:00007ffd26861108 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000055558877e500 RCX: 00007f4c33c1e68e
RDX: 0000000000000001 RSI: 00007ffd26861190 RDI: 0000000000000005
RBP: 00007f4c33cf45f2 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffd26861190 R14: 00007f4c34a05620 R15: 0000000000000003
 </TASK>
INFO: task syz.6.2437:14016 blocked for more than 145 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.6.2437      state:D stack:27472 pid:14016 ppid: 11879 flags:0x00004004
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
 rcu_barrier+0xa1/0x4c0 kernel/rcu/tree.c:4043
 netdev_run_todo+0x2fd/0xa70 net/core/dev.c:10688
 tun_detach drivers/net/tun.c:705 [inline]
 tun_chr_close+0x13b/0x1b0 drivers/net/tun.c:3440
 __fput+0x234/0x930 fs/file_table.c:311
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
 __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: 0033:0x7f059b37ae59
RSP: 002b:00007ffc680b62e8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007f059b5f5da0 RCX: 00007f059b37ae59
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f059b5f5da0 R08: 00007f059b5f4038 R09: 0000000000000000
R10: 00000000005ecaa4 R11: 0000000000000246 R12: 000000000009b322
R13: 00007f059b5f409c R14: 000000000009b154 R15: 00007f059b5f4090
 </TASK>
INFO: task syz.3.2438:14026 blocked for more than 145 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.2438      state:D stack:27216 pid:14026 ppid: 12779 flags:0x00004004
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
 rcu_barrier+0xa1/0x4c0 kernel/rcu/tree.c:4043
 netdev_run_todo+0x2fd/0xa70 net/core/dev.c:10688
 tun_detach drivers/net/tun.c:705 [inline]
 tun_chr_close+0x13b/0x1b0 drivers/net/tun.c:3440
 __fput+0x234/0x930 fs/file_table.c:311
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
 __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: 0033:0x7eff210cee59
RSP: 002b:00007eff1f307028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: 0000000000000007 RBX: 00007eff21348090 RCX: 00007eff210cee59
RDX: 0000200000000040 RSI: 00000000400454d1 RDI: 0000000000000004
RBP: 00007eff21164d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007eff21348128 R14: 00007eff21348090 R15: 00007ffd503907c8
 </TASK>
INFO: task syz.0.2446:14097 blocked for more than 146 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.2446      state:D stack:27376 pid:14097 ppid:  4193 flags:0x00004004
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
 rcu_barrier+0xa1/0x4c0 kernel/rcu/tree.c:4043
 netdev_run_todo+0x2fd/0xa70 net/core/dev.c:10688
 tun_detach drivers/net/tun.c:705 [inline]
 tun_chr_close+0x13b/0x1b0 drivers/net/tun.c:3440
 __fput+0x234/0x930 fs/file_table.c:311
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
 __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: 0033:0x7f81a0023e59
RSP: 002b:00007ffd62187ec8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007f81a029eda0 RCX: 00007f81a0023e59
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f81a029eda0 R08: 00007f81a029d038 R09: 0000000000000000
R10: 00000000005e99ac R11: 0000000000000246 R12: 000000000009c5d2
R13: 00007f81a029d09c R14: 000000000009c3b2 R15: 00007f81a029d090
 </TASK>
INFO: task syz-executor:14180 blocked for more than 146 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:22512 pid:14180 ppid:     1 flags:0x00004004
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
 del_device_store+0xd3/0x3a0 drivers/net/netdevsim/bus.c:344
 kernfs_fop_write_iter+0x379/0x4c0 fs/kernfs/file.c:296
 call_write_iter include/linux/fs.h:2173 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x745/0xd60 fs/read_write.c:594
 ksys_write+0x152/0x260 fs/read_write.c:647
 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: 0033:0x7facd528568e
RSP: 002b:00007fffed27e398 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00005555896a0500 RCX: 00007facd528568e
RDX: 0000000000000001 RSI: 00007fffed27e420 RDI: 0000000000000005
RBP: 00007facd535b5f2 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007fffed27e420 R14: 00007facd606c620 R15: 0000000000000003
 </TASK>
INFO: task syz-executor:14185 blocked for more than 147 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:22512 pid:14185 ppid:     1 flags:0x00004004
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
 del_device_store+0xd3/0x3a0 drivers/net/netdevsim/bus.c:344
 kernfs_fop_write_iter+0x379/0x4c0 fs/kernfs/file.c:296
 call_write_iter include/linux/fs.h:2173 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x745/0xd60 fs/read_write.c:594
 ksys_write+0x152/0x260 fs/read_write.c:647
 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: 0033:0x7f7c143e468e
RSP: 002b:00007ffce8aad248 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000555581276500 RCX: 00007f7c143e468e
RDX: 0000000000000001 RSI: 00007ffce8aad2d0 RDI: 0000000000000005
RBP: 00007f7c144ba5f2 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffce8aad2d0 R14: 00007f7c151cb620 R15: 0000000000000003
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/27:
 #0: ffffffff8c31f320 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
5 locks held by kworker/u4:3/156:
 #0: ffff888016dcd938 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x761/0x1010 kernel/workqueue.c:-1
 #1: ffffc90002067d00 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x79f/0x1010 kernel/workqueue.c:2285
 #2: ffffffff8d431cd0 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net+0x148/0xba0 net/core/net_namespace.c:589
 #3: ffff88805a5413e8 (&wg->device_update_lock){+.+.}-{3:3}, at: wg_destruct+0x112/0x300 drivers/net/wireguard/device.c:233
 #4: ffffffff8c323cb0 (rcu_state.barrier_mutex){+.+.}-{3:3}, at: rcu_barrier+0xa1/0x4c0 kernel/rcu/tree.c:4043
2 locks held by getty/3951:
 #0: ffff88802c066098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
 #1: ffffc900025ce2e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x5df/0x1a70 drivers/tty/n_tty.c:2158
3 locks held by kworker/0:4/4228:
3 locks held by kworker/1:8/5663:
 #0: ffff888016c70938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x761/0x1010 kernel/workqueue.c:-1
 #1: ffffc900031efd00 ((work_completion)(&(&nsim_dev->trap_data->trap_report_dw)->work)){+.+.}-{0:0}, at: process_one_work+0x79f/0x1010 kernel/workqueue.c:2285
 #2: ffff88802b7e9400 (&nsim_dev->port_list_lock){+.+.}-{3:3}, at: nsim_dev_trap_report_work+0x56/0xb40 drivers/net/netdevsim/dev.c:757
3 locks held by kworker/u4:0/10902:
1 lock held by syz-executor/13136:
 #0: ffffffff8c323cb0 (rcu_state.barrier_mutex){+.+.}-{3:3}, at: rcu_barrier+0xa1/0x4c0 kernel/rcu/tree.c:4043
7 locks held by syz-executor/13933:
 #0: ffff88807f190460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x295/0xd60 fs/read_write.c:590
 #1: ffff88805b8b3888 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
 #2: ffff888023145490 (kn->active#284){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:288
 #3: ffffffff8cd7aaa8 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xd3/0x3a0 drivers/net/netdevsim/bus.c:344
 #4: ffff88802b7ea178 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:764 [inline]
 #4: ffff88802b7ea178 (&dev->mutex){....}-{3:3}, at: __device_driver_lock drivers/base/dd.c:1044 [inline]
 #4: ffff88802b7ea178 (&dev->mutex){....}-{3:3}, at: device_release_driver_internal+0xb0/0x750 drivers/base/dd.c:1259
 #5: ffff88802b7e9400 (&nsim_dev->port_list_lock){+.+.}-{3:3}, at: nsim_dev_port_del_all drivers/net/netdevsim/dev.c:1359 [inline]
 #5: ffff88802b7e9400 (&nsim_dev->port_list_lock){+.+.}-{3:3}, at: nsim_dev_reload_destroy+0x115/0x240 drivers/net/netdevsim/dev.c:1561
 #6: ffffffff8c323cb0 (rcu_state.barrier_mutex){+.+.}-{3:3}, at: rcu_barrier+0xa1/0x4c0 kernel/rcu/tree.c:4043
4 locks held by syz-executor/14007:
 #0: ffff88807f190460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x295/0xd60 fs/read_write.c:590
 #1: ffff88807a454c88 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
 #2: ffff888023145490 (kn->active#284){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:288
 #3: ffffffff8cd7aaa8 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xd3/0x3a0 drivers/net/netdevsim/bus.c:344
1 lock held by syz.6.2437/14016:
 #0: ffffffff8c323cb0 (rcu_state.barrier_mutex){+.+.}-{3:3}, at: rcu_barrier+0xa1/0x4c0 kernel/rcu/tree.c:4043
1 lock held by syz.3.2438/14026:
 #0: ffffffff8c323cb0 (rcu_state.barrier_mutex){+.+.}-{3:3}, at: rcu_barrier+0xa1/0x4c0 kernel/rcu/tree.c:4043
1 lock held by syz.0.2446/14097:
 #0: ffffffff8c323cb0 (rcu_state.barrier_mutex){+.+.}-{3:3}, at: rcu_barrier+0xa1/0x4c0 kernel/rcu/tree.c:4043
4 locks held by syz-executor/14180:
 #0: ffff88807f190460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x295/0xd60 fs/read_write.c:590
 #1: ffff88804e01dc88 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
 #2: ffff888023145490 (kn->active#284){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:288
 #3: ffffffff8cd7aaa8 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xd3/0x3a0 drivers/net/netdevsim/bus.c:344
4 locks held by syz-executor/14185:
 #0: ffff88807f190460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x295/0xd60 fs/read_write.c:590
 #1: ffff88802255e888 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
 #2: ffff888023145490 (kn->active#284){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:288
 #3: ffffffff8cd7aaa8 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xd3/0x3a0 drivers/net/netdevsim/bus.c:344
4 locks held by syz-executor/14198:
 #0: ffff88807f190460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x295/0xd60 fs/read_write.c:590
 #1: ffff888073a36488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
 #2: ffff888023145490 (kn->active#284){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:288
 #3: ffffffff8cd7aaa8 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xd3/0x3a0 drivers/net/netdevsim/bus.c:344
4 locks held by syz-executor/14209:
 #0: ffff88807f190460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x295/0xd60 fs/read_write.c:590
 #1: ffff888060516888 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
 #2: ffff888023145490 (kn->active#284){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:288
 #3: ffffffff8cd7aaa8 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xd3/0x3a0 drivers/net/netdevsim/bus.c:344
4 locks held by syz-executor/14222:
 #0: ffff88807f190460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x295/0xd60 fs/read_write.c:590
 #1: ffff8880606cc488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
 #2: ffff888023145490 (kn->active#284){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:288
 #3: ffffffff8cd7aaa8 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xd3/0x3a0 drivers/net/netdevsim/bus.c:344
4 locks held by syz-executor/14239:
 #0: ffff88807f190460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x295/0xd60 fs/read_write.c:590
 #1: ffff888061baf488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
 #2: ffff888023145490 (kn->active#284){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:288
 #3: ffffffff8cd7aaa8 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xd3/0x3a0 drivers/net/netdevsim/bus.c:344
4 locks held by syz-executor/14241:
 #0: ffff88807f190460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x295/0xd60 fs/read_write.c:590
 #1: ffff888025526c88 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
 #2: ffff888023145490 (kn->active#284){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:288
 #3: ffffffff8cd7aaa8 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xd3/0x3a0 drivers/net/netdevsim/bus.c:344
4 locks held by syz-executor/14257:
 #0: ffff88807f190460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x295/0xd60 fs/read_write.c:590
 #1: ffff888146a91488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
 #2: ffff888023145490 (kn->active#284){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:288
 #3: ffffffff8cd7aaa8 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xd3/0x3a0 drivers/net/netdevsim/bus.c:344
4 locks held by syz-executor/14268:
 #0: ffff88807f190460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x295/0xd60 fs/read_write.c:590
 #1: ffff888060c29c88 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
 #2: ffff888023145490 (kn->active#284){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:288
 #3: ffffffff8cd7aaa8 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xd3/0x3a0 drivers/net/netdevsim/bus.c:344
4 locks held by syz-executor/14282:
 #0: ffff88807f190460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x295/0xd60 fs/read_write.c:590
 #1: ffff8881477dbc88 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
 #2: ffff888023145490 (kn->active#284){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:288
 #3: ffffffff8cd7aaa8 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xd3/0x3a0 drivers/net/netdevsim/bus.c:344
4 locks held by syz-executor/14298:
 #0: ffff88807f190460 (
sb_writers
#8){.+.+}-{0:0}, at: vfs_write+0x295/0xd60 fs/read_write.c:590
 #1: ffff888062fcdc88 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
 #2: ffff888023145490 (kn->active#284){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:288
 #3: ffffffff8cd7aaa8 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xd3/0x3a0 drivers/net/netdevsim/bus.c:344
4 locks held by syz-executor/14299:
 #0: ffff88807f190460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x295/0xd60 fs/read_write.c:590
 #1: ffff88803b49c888 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
 #2: ffff888023145490 (kn->active#284){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:288
 #3: ffffffff8cd7aaa8 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xd3/0x3a0 drivers/net/netdevsim/bus.c:344
4 locks held by syz-executor/14317:
 #0: ffff88807f190460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x295/0xd60 fs/read_write.c:590
 #1: ffff88804af1d488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
 #2: ffff888023145490 (kn->active#284){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:288
 #3: ffffffff8cd7aaa8 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: del_device_store+0xd3/0x3a0 drivers/net/netdevsim/bus.c:344

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

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: 14 Comm: ksoftirqd/0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:__preempt_count_add arch/x86/include/asm/preempt.h:80 [inline]
RIP: 0010:kvm_clock_read arch/x86/kernel/kvmclock.c:78 [inline]
RIP: 0010:kvm_sched_clock_read+0x0/0x40 arch/x86/kernel/kvmclock.c:91
Code: c7 60 87 28 8a 89 c6 48 89 da 48 c7 c1 60 88 28 8a 5b e9 83 58 7d 08 89 cf 48 89 de 31 d2 e8 27 ce cf 02 eb d4 0f 1f 44 00 00 <65> ff 05 61 a6 cd 7e 65 48 8b 3d 21 ab cd 7e e8 bc 05 00 00 65 ff
RSP: 0018:ffffc90000007a88 EFLAGS: 00000086
RAX: ffffffff819bb7bb RBX: ffff8880791a29c8 RCX: ffff88813fe29dc0
RDX: 0000000000010100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000007d30 R08: ffffc90000007c7f R09: ffffc90000007b80
R10: dffffc0000000000 R11: fffff52000000f90 R12: ffffffff8c3a4f88
R13: ffff8880791a2a60 R14: ffff8880791a29c8 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f819e27cff8 CR3: 000000007576e000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000200000000300 DR2: 0000200000000300
DR3: 0000200000000300 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 sched_clock_cpu+0x15/0x3c0 kernel/sched/clock.c:371
 local_clock include/linux/sched/clock.h:84 [inline]
 cpu_clock_event_update kernel/events/core.c:11011 [inline]
 cpu_clock_event_read+0x17/0x50 kernel/events/core.c:11044
 perf_swevent_hrtimer+0x161/0x5b0 kernel/events/core.c:10927
 __run_hrtimer kernel/time/hrtimer.c:1685 [inline]
 __hrtimer_run_queues+0x4b4/0xb70 kernel/time/hrtimer.c:1749
 hrtimer_interrupt+0x3bb/0x8d0 kernel/time/hrtimer.c:1811
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
 __sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:check_kcov_mode kernel/kcov.c:172 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:227 [inline]
RIP: 0010:__sanitizer_cov_trace_const_cmp8+0x13/0x80 kernel/kcov.c:300
Code: 4a 89 7c 02 10 4a 89 74 02 18 4a 89 44 02 20 48 ff c1 48 89 0a c3 90 48 8b 04 24 65 48 8b 0d c4 35 89 7e 65 8b 15 c5 35 89 7e <81> e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 57 83 b9 34 16 00 00
RSP: 0018:ffffc90000d36a78 EFLAGS: 00000246
RAX: ffffffff840757e3 RBX: ffff0a0000000604 RCX: ffff88813fe29dc0
RDX: 0000000000000101 RSI: ffff0a0000000604 RDI: 0001000000000000
RBP: ffffffff8a2be7c4 R08: ffff88813fe29dc0 R09: 0000000000000012
R10: 0000000000000012 R11: 0000000000000100 R12: ffffc90000d36ca0
R13: 0001000000000000 R14: ffffc90000d36daf R15: 0000000000000000
 string_nocheck lib/vsprintf.c:641 [inline]
 string+0xb3/0x2b0 lib/vsprintf.c:724
 vsnprintf+0x10da/0x1c20 lib/vsprintf.c:2811
 sprintf+0xe4/0x140 lib/vsprintf.c:3013
 print_caller kernel/printk/printk.c:1285 [inline]
 info_print_prefix+0x20c/0x360 kernel/printk/printk.c:1302
 record_print_text kernel/printk/printk.c:1349 [inline]
 console_unlock+0x66e/0x1120 kernel/printk/printk.c:2725
 vprintk_emit+0xc0/0x150 kernel/printk/printk.c:2274
 _printk+0xda/0x130 kernel/printk/printk.c:2299
 br_fdb_update+0x572/0x5b0 net/bridge/br_fdb.c:596
 br_handle_frame_finish+0x3e0/0x1310 net/bridge/br_input.c:106
 br_nf_hook_thresh+0x3c9/0x4a0 net/bridge/br_netfilter_hooks.c:1155
 br_nf_pre_routing_finish_ipv6+0x9c2/0xc90 net/bridge/br_netfilter_ipv6.c:-1
 NF_HOOK include/linux/netfilter.h:302 [inline]
 br_nf_pre_routing_ipv6+0x355/0x680 net/bridge/br_netfilter_ipv6.c:237
 nf_hook_entry_hookfn include/linux/netfilter.h:142 [inline]
 nf_hook_bridge_pre net/bridge/br_input.c:242 [inline]
 br_handle_frame+0xec7/0x10e0 net/bridge/br_input.c:384
 __netif_receive_skb_core+0xfef/0x3690 net/core/dev.c:5445
 __netif_receive_skb_one_core net/core/dev.c:5549 [inline]
 __netif_receive_skb+0x74/0x290 net/core/dev.c:5665
 process_backlog+0x370/0x790 net/core/dev.c:6542
 __napi_poll+0xc0/0x430 net/core/dev.c:7101
 napi_poll net/core/dev.c:7168 [inline]
 net_rx_action+0x4d4/0xa10 net/core/dev.c:7258
 handle_softirqs+0x339/0x830 kernel/softirq.c:576
 run_ksoftirqd+0xa4/0x100 kernel/softirq.c:943
 smpboot_thread_fn+0x4f6/0x970 kernel/smpboot.c:164
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/20 20:36 linux-5.15.y 93741761e5e3 62fb93a2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: task hung in nsim_dev_trap_report_work
2026/03/31 17:36 linux-5.15.y 91d48252ad4b aeea1c72 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: task hung in nsim_dev_trap_report_work
2026/03/02 23:30 linux-5.15.y 3330a8d33e08 b9dd6534 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: task hung in nsim_dev_trap_report_work
2025/12/05 08:36 linux-5.15.y cc5ec8769306 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: task hung in nsim_dev_trap_report_work
* Struck through repros no longer work on HEAD.