syzbot

INFO: task syz.5.688:12541 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.5.688       state:D stack:25640 pid:12541 tgid:12505 ppid:10662  task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5388 [inline]
 __schedule+0x16d8/0x55e0 kernel/sched/core.c:7189
 __schedule_loop kernel/sched/core.c:7268 [inline]
 schedule+0x164/0x360 kernel/sched/core.c:7283
 percpu_rwsem_wait+0x32d/0x4a0 kernel/locking/percpu-rwsem.c:164
 __percpu_down_read+0xf8/0x140 kernel/locking/percpu-rwsem.c:180
 percpu_down_read_internal include/linux/percpu-rwsem.h:67 [inline]
 percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
 __sb_start_write include/linux/fs/super.h:19 [inline]
 sb_start_write+0x18e/0x1c0 include/linux/fs/super.h:125
 mnt_want_write+0x41/0x90 fs/namespace.c:493
 filename_create+0x154/0x370 fs/namei.c:4943
 filename_mkdirat+0xd2/0x520 fs/namei.c:5297
 __do_sys_mkdirat fs/namei.c:5325 [inline]
 __se_sys_mkdirat+0x35/0x150 fs/namei.c:5322
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fdd2d9cce59
RSP: 002b:00007fdd2bbfd028 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007fdd2dc46090 RCX: 00007fdd2d9cce59
RDX: 0000000000000000 RSI: 0000200000000100 RDI: ffffffffffffff9c
RBP: 00007fdd2da62d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdd2dc46128 R14: 00007fdd2dc46090 R15: 00007ffcb3b5c878
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/37:
 #0: ffffffff8ddc7b60 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #0: ffffffff8ddc7b60 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
 #0: ffffffff8ddc7b60 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
3 locks held by kworker/u8:3/56:
2 locks held by kworker/u8:5/110:
 #0: ffff888019c34138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3289 [inline]
 #0: ffff888019c34138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3397
 #1: ffffc9000155fc40 ((reaper_work).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3289 [inline]
 #1: ffffc9000155fc40 ((reaper_work).work){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3397
3 locks held by kworker/u8:6/162:
 #0: ffff888019c34138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3289 [inline]
 #0: ffff888019c34138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3397
 #1: ffffc9000397fc40 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3289 [inline]
 #1: ffffc9000397fc40 ((linkwatch_work).work){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3397
 #2: ffffffff8f1484b8 (rtnl_mutex){+.+.}-{4:4}, at: linkwatch_event+0xe/0x60 net/core/link_watch.c:313
3 locks held by kworker/u8:8/825:
 #0: ffff88803250c938 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3289 [inline]
 #0: ffff88803250c938 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3397
 #1: ffffc9000463fc40 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3289 [inline]
 #1: ffffc9000463fc40 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3397
 #2: ffffffff8f1484b8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
 #2: ffffffff8f1484b8 (rtnl_mutex){+.+.}-{4:4}, at: addrconf_dad_work+0x123/0x16e0 net/ipv6/addrconf.c:4208
3 locks held by kworker/u8:10/1402:
 #0: ffff88802ac5f138 ((wq_completion)loop9){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3289 [inline]
 #0: ffff88802ac5f138 ((wq_completion)loop9){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3397
 #1: ffffc90006a27c40 ((work_completion)(&worker->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3289 [inline]
 #1: ffffc90006a27c40 ((work_completion)(&worker->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3397
 #2: ffff888026632160 (&lo->lo_work_lock){+.+.}-{3:3}, at: spin_lock_irq include/linux/spinlock_rt.h:96 [inline]
 #2: ffff888026632160 (&lo->lo_work_lock){+.+.}-{3:3}, at: loop_process_work+0x125/0x11d0 drivers/block/loop.c:1953
6 locks held by kworker/u8:15/1507:
2 locks held by dhcpcd/5267:
 #0: ffff88806401c928 (nlk_cb_mutex-ROUTE){+.+.}-{4:4}, at: __netlink_dump_start+0xf4/0x7b0 net/netlink/af_netlink.c:2409
 #1: ffffffff8f1484b8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
 #1: ffffffff8f1484b8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_dumpit+0x92/0x200 net/core/rtnetlink.c:6865
2 locks held by getty/5360:
 #0: ffff888036bf50a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90003cc62e0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x460/0x1390 drivers/tty/n_tty.c:2211
3 locks held by kworker/0:6/5618:
 #0: ffff88813fe33938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3289 [inline]
 #0: ffff88813fe33938 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3397
 #1: ffffc900044cfc40 ((work_completion)(&data->fib_event_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3289 [inline]
 #1: ffffc900044cfc40 ((work_completion)(&data->fib_event_work)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3397
 #2: ffff88805ead8280 (&data->fib_lock){+.+.}-{4:4}, at: nsim_fib_event_work+0x222/0x3e0 drivers/net/netdevsim/fib.c:1490
1 lock held by syz-executor/10795:
 #0: ffff88802a1fe480 (sb_writers#5){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:493
2 locks held by kworker/u8:0/11954:
 #0: ffff888019c34138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3289 [inline]
 #0: ffff888019c34138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3397
 #1: ffffc900069b7c40 (connector_reaper_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3289 [inline]
 #1: ffffc900069b7c40 (connector_reaper_work){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3397
1 lock held by syz.5.688/12541:
 #0: ffff888037fe0480 (sb_writers#13){++++}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:493
1 lock held by udevd/13724:
 #0: ffff88803775e480 (sb_writers#5){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:493
1 lock held by syz-executor/13847:
 #0: ffffffff8f1484b8 (rtnl_mutex){+.+.}-{4:4}, at: tun_detach drivers/net/tun.c:634 [inline]
 #0: ffffffff8f1484b8 (rtnl_mutex){+.+.}-{4:4}, at: tun_chr_close+0x41/0x1c0 drivers/net/tun.c:3442
4 locks held by syz-executor/14081:
 #0: ffff888037414480 (sb_writers#7){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2724 [inline]
 #0: ffff888037414480 (sb_writers#7){.+.+}-{0:0}, at: vfs_write+0x231/0xbb0 fs/read_write.c:684
 #1: ffff888060e25878 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1d9/0x540 fs/kernfs/file.c:343
 #2: ffff8880291b05a8 (kn->active#53){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #2: ffff8880291b05a8 (kn->active#53){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x22c/0x540 fs/kernfs/file.c:344
 #3: ffffffff8e9ce938 (nsim_bus_dev_list_lock){+.+.}-{4:4}, at: new_device_store+0x13c/0x710 drivers/net/netdevsim/bus.c:184
7 locks held by syz-executor/14160:
 #0: ffff888037414480 (sb_writers#7){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2724 [inline]
 #0: ffff888037414480 (sb_writers#7){.+.+}-{0:0}, at: vfs_write+0x231/0xbb0 fs/read_write.c:684
 #1: ffff88802c379078 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1d9/0x540 fs/kernfs/file.c:343
 #2: ffff8880291b04b8 (kn->active#52){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #2: ffff8880291b04b8 (kn->active#52){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x22c/0x540 fs/kernfs/file.c:344
 #3: ffffffff8e9ce938 (nsim_bus_dev_list_lock){+.+.}-{4:4}, at: del_device_store+0xd6/0x370 drivers/net/netdevsim/bus.c:234
 #4: ffff88805da24160 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:1040 [inline]
 #4: ffff88805da24160 (&dev->mutex){....}-{4:4}, at: __device_driver_lock drivers/base/dd.c:1174 [inline]
 #4: ffff88805da24160 (&dev->mutex){....}-{4:4}, at: device_release_driver_internal+0xb9/0x880 drivers/base/dd.c:1372
 #5: ffff888037316310 (&devlink->lock_key#9){+.+.}-{4:4}, at: nsim_drv_remove+0x50/0x160 drivers/net/netdevsim/dev.c:1799
 #6: ffffffff8ddcdcf0 (rcu_state.barrier_mutex){+.+.}-{4:4}, at: rcu_barrier+0x4c/0x530 kernel/rcu/tree.c:3828
1 lock held by syz-executor/14535:
 #0: ffffffff8f1484b8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
 #0: ffffffff8f1484b8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline]
 #0: ffffffff8f1484b8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0x8a3/0x1bd0 net/core/rtnetlink.c:4109
4 locks held by syz.9.905/14549:

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 37 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline]
 __sys_info lib/sys_info.c:157 [inline]
 sys_info+0x135/0x170 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
 watchdog+0xfd7/0x1030 kernel/hung_task.c:561
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 56 Comm: kworker/u8:3 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Workqueue: bat_events batadv_dat_purge
RIP: 0010:check_wait_context kernel/locking/lockdep.c:4882 [inline]
RIP: 0010:__lock_acquire+0x579/0x2cc0 kernel/locking/lockdep.c:5187
Code: 85 c0 74 1c 83 3d ba ed c7 0d 00 75 13 48 8d 3d 9d 07 cb 0d 48 c7 c6 80 f7 50 8d 67 48 0f b9 3a 90 31 c9 0f b6 81 c4 00 00 00 <84> c0 0f 84 77 ff ff ff 41 0f b6 f4 0f b6 d0 40 38 c6 0f 42 d6 80
RSP: 0018:ffffc9000122f7c0 EFLAGS: 00000002
RAX: 0000000000000003 RBX: ffff88801a73ca10 RCX: ffffffff92f0bbc8
RDX: 0000000000000003 RSI: 0000000000000005 RDI: 0000000000000000
RBP: 0000000000000001 R08: ffffffff8b1955a7 R09: 0000000000080000
R10: 0000000000000000 R11: ffff888063c45098 R12: 0000000000000003
R13: ffff88801a73ca40 R14: ffff88801a73bd80 R15: 0000000000000003
FS:  0000000000000000(0000) GS:ffff8881263a1000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b3340fff8 CR3: 0000000037908000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline]
 _raw_spin_lock_irqsave+0x40/0x60 kernel/locking/spinlock.c:166
 rtlock_slowlock kernel/locking/rtmutex.c:1916 [inline]
 rtlock_lock kernel/locking/spinlock_rt.c:43 [inline]
 __rt_spin_lock kernel/locking/spinlock_rt.c:49 [inline]
 rt_spin_lock+0x157/0x400 kernel/locking/spinlock_rt.c:57
 spin_lock_bh include/linux/spinlock_rt.h:90 [inline]
 __batadv_dat_purge+0x131/0x400 net/batman-adv/distributed-arp-table.c:173
 batadv_dat_purge+0x20/0x70 net/batman-adv/distributed-arp-table.c:204
 process_one_work kernel/workqueue.c:3314 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3397
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3478
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>