syzbot

INFO: task syz.4.1812:21990 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.1812      state:D stack:25304 pid:21990 tgid:21986 ppid:5604   task_flags:0x400140 flags:0x00080003
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5388 [inline]
 __schedule+0x16ec/0x5620 kernel/sched/core.c:7189
 __schedule_loop kernel/sched/core.c:7268 [inline]
 schedule+0x164/0x360 kernel/sched/core.c:7283
 schedule_timeout+0xc3/0x2c0 kernel/time/sleep_timeout.c:75
 do_wait_for_common kernel/sched/completion.c:100 [inline]
 __wait_for_common kernel/sched/completion.c:121 [inline]
 wait_for_common kernel/sched/completion.c:132 [inline]
 wait_for_completion+0x2cc/0x5e0 kernel/sched/completion.c:153
 kthread_flush_worker+0x138/0x1a0 kernel/kthread.c:1579
 __alloc_workqueue+0x15f5/0x1f40 kernel/workqueue.c:5909
 alloc_workqueue_va kernel/workqueue.c:5931 [inline]
 alloc_workqueue_noprof+0xe3/0x210 kernel/workqueue.c:5947
 btrfs_alloc_workqueue+0x1ec/0x2d0 fs/btrfs/async-thread.c:112
 btrfs_init_workqueues+0x348/0x680 fs/btrfs/disk-io.c:1962
 open_ctree+0x1598/0x4190 fs/btrfs/disk-io.c:3444
 btrfs_fill_super fs/btrfs/super.c:981 [inline]
 btrfs_get_tree_super fs/btrfs/super.c:1944 [inline]
 btrfs_get_tree_subvol fs/btrfs/super.c:2087 [inline]
 btrfs_get_tree+0x1061/0x1910 fs/btrfs/super.c:2121
 vfs_get_tree+0x92/0x2a0 fs/super.c:1754
 fc_mount fs/namespace.c:1193 [inline]
 do_new_mount_fc fs/namespace.c:3758 [inline]
 do_new_mount+0x341/0xd30 fs/namespace.c:3834
 do_mount fs/namespace.c:4167 [inline]
 __do_sys_mount fs/namespace.c:4383 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4360
 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: 0033:0x7f1a5c87e0ca
RSP: 002b:00007f1a5aacde58 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f1a5aacdee0 RCX: 00007f1a5c87e0ca
RDX: 0000200000005100 RSI: 0000200000000000 RDI: 00007f1a5aacdea0
RBP: 0000200000005100 R08: 00007f1a5aacdee0 R09: 0000000000000810
R10: 0000000000000810 R11: 0000000000000246 R12: 0000200000000000
R13: 00007f1a5aacdea0 R14: 000000000000512d R15: 0000200000000080
 </TASK>

Showing all locks held in the system:
3 locks held by kworker/u8:0/12:
 #0: ffff888031f07938 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3289 [inline]
 #0: ffff888031f07938 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_scheduled_works+0xa35/0x1860 kernel/workqueue.c:3397
 #1: ffffc90000117c40 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3290 [inline]
 #1: ffffc90000117c40 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa70/0x1860 kernel/workqueue.c:3397
 #2: ffffffff8f350538 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
 #2: ffffffff8f350538 (rtnl_mutex){+.+.}-{4:4}, at: addrconf_dad_work+0x124/0x1680 net/ipv6/addrconf.c:4206
1 lock held by khungtaskd/38:
 #0: ffffffff8dfc8100 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #0: ffffffff8dfc8100 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
 #0: ffffffff8dfc8100 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
6 locks held by kworker/u8:9/1169:
 #0: ffff88801b290938 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3289 [inline]
 #0: ffff88801b290938 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0xa35/0x1860 kernel/workqueue.c:3397
 #1: ffffc90006107c40 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3290 [inline]
 #1: ffffc90006107c40 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0xa70/0x1860 kernel/workqueue.c:3397
 #2: ffffffff8f3417e0 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xf4/0x800 net/core/net_namespace.c:673
 #3: ffff88803ee08160 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:1040 [inline]
 #3: ffff88803ee08160 (&dev->mutex){....}-{4:4}, at: devl_dev_lock net/devlink/devl_internal.h:124 [inline]
 #3: ffff88803ee08160 (&dev->mutex){....}-{4:4}, at: devlink_pernet_pre_exit+0x129/0x420 net/devlink/core.c:557
 #4: ffff888065984310 (&devlink->lock_key#7){+.+.}-{4:4}, at: devl_lock net/devlink/core.c:292 [inline]
 #4: ffff888065984310 (&devlink->lock_key#7){+.+.}-{4:4}, at: devl_dev_lock net/devlink/devl_internal.h:125 [inline]
 #4: ffff888065984310 (&devlink->lock_key#7){+.+.}-{4:4}, at: devlink_pernet_pre_exit+0x142/0x420 net/devlink/core.c:557
 #5: ffffffff8f350538 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
 #5: ffffffff8f350538 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_dev_lock+0x257/0x2f0 net/core/dev.c:2162
5 locks held by kworker/u8:11/1478:
2 locks held by getty/5355:
 #0: ffff8880369650a0 (&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+0x462/0x13a0 drivers/tty/n_tty.c:2211
2 locks held by udevd/5591:
 #0: ffff888011884480 (sb_writers#5){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:493
 #1: ffff88803d978388 (&type->i_mutex_dir_key#5/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1074 [inline]
 #1: ffff88803d978388 (&type->i_mutex_dir_key#5/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2914 [inline]
 #1: ffff88803d978388 (&type->i_mutex_dir_key#5/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2938 [inline]
 #1: ffff88803d978388 (&type->i_mutex_dir_key#5/1){+.+.}-{4:4}, at: filename_rmdir+0x1cd/0x520 fs/namei.c:5424
1 lock held by syz-executor/5605:
 #0: ffffffff8f350538 (rtnl_mutex){+.+.}-{4:4}, at: tun_detach drivers/net/tun.c:634 [inline]
 #0: ffffffff8f350538 (rtnl_mutex){+.+.}-{4:4}, at: tun_chr_close+0x41/0x1c0 drivers/net/tun.c:3441
3 locks held by kworker/0:4/5614:
1 lock held by udevd/5622:
 #0: ffff888011884480 (sb_writers#5){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:493
3 locks held by kworker/u8:8/9929:
 #0: ffff88801a074138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3289 [inline]
 #0: ffff88801a074138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0xa35/0x1860 kernel/workqueue.c:3397
 #1: ffffc900064f7c40 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3290 [inline]
 #1: ffffc900064f7c40 ((linkwatch_work).work){+.+.}-{0:0}, at: process_scheduled_works+0xa70/0x1860 kernel/workqueue.c:3397
 #2: ffffffff8f350538 (rtnl_mutex){+.+.}-{4:4}, at: linkwatch_event+0xe/0x60 net/core/link_watch.c:313
1 lock held by syz-executor/15003:
1 lock held by udevd/20726:
 #0: ffff88801c6d4480 (sb_writers){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:493
1 lock held by syz.4.1812/21990:
 #0: ffff8880298f20d0 (&type->s_umount_key#51/1){+.+.}-{4:4}, at: alloc_super+0x28c/0xac0 fs/super.c:345
3 locks held by kworker/0:5/22579:
 #0: ffff88801a037938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3289 [inline]
 #0: ffff88801a037938 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0xa35/0x1860 kernel/workqueue.c:3397
 #1: ffffc900153d7c40 (rx_mode_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3290 [inline]
 #1: ffffc900153d7c40 (rx_mode_work){+.+.}-{0:0}, at: process_scheduled_works+0xa70/0x1860 kernel/workqueue.c:3397
 #2: ffffffff8f350538 (rtnl_mutex){+.+.}-{4:4}, at: netdev_rx_mode_work+0x1c/0x450 net/core/dev_addr_lists.c:1312
1 lock held by syz-executor/23415:
 #0: ffffffff8f350538 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
 #0: ffffffff8f350538 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline]
 #0: ffffffff8f350538 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0x883/0x1bb0 net/core/rtnetlink.c:4109
2 locks held by syz-executor/23603:
 #0: ffffffff8f8a5708 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #0: ffffffff8f8a5708 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
 #0: ffffffff8f8a5708 (&ops->srcu#2){.+.+}-{0:0}, at: rtnl_link_ops_get+0x23/0x250 net/core/rtnetlink.c:570
 #1: ffffffff8f350538 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
 #1: ffffffff8f350538 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline]
 #1: ffffffff8f350538 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0x883/0x1bb0 net/core/rtnetlink.c:4109
3 locks held by syz.8.1989/23724:
6 locks held by dhcpcd-run-hook/23728:

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 38 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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+0xfd3/0x1030 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 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 1478 Comm: kworker/u8:11 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: bat_events batadv_tt_purge
RIP: 0010:check_wait_context kernel/locking/lockdep.c:4877 [inline]
RIP: 0010:__lock_acquire+0x4fb/0x2cf0 kernel/locking/lockdep.c:5187
Code: 0b 00 00 0f 8d f5 00 00 00 4c 63 fb 4b 8d 04 bf 49 8d 1c c6 48 81 c3 18 0c 00 00 eb 1d 44 89 e0 49 ff c7 49 63 8e f0 0b 00 00 <48> 83 c3 28 41 89 c4 49 39 cf 0f 8d c7 00 00 00 49 83 ff 31 0f 83
RSP: 0018:ffffc90006a77718 EFLAGS: 00000007
RAX: 0000000000000003 RBX: ffff888029d90cb8 RCX: 0000000000000005
RDX: 0000000000000003 RSI: 0000000000000003 RDI: 0000000000000000
RBP: ffff888029d90cc0 R08: ffffffff8b1deb60 R09: ffffffff8dfc8100
R10: dffffc0000000000 R11: fffffbfff1f10dff R12: 0000000000000003
R13: ffff888029d90cc0 R14: ffff888029d90000 R15: 0000000000000005
FS:  0000000000000000(0000) GS:ffff888126287000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc3e82e9298 CR3: 0000000050e4e000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
 rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 rcu_read_lock include/linux/rcupdate.h:838 [inline]
 __rt_spin_lock kernel/locking/spinlock_rt.c:50 [inline]
 rt_spin_lock+0x1fc/0x400 kernel/locking/spinlock_rt.c:57
 spin_lock_bh include/linux/spinlock_rt.h:90 [inline]
 batadv_tt_local_purge+0x143/0x380 net/batman-adv/translation-table.c:1353
 batadv_tt_purge+0x35/0xa10 net/batman-adv/translation-table.c:3549
 process_one_work kernel/workqueue.c:3314 [inline]
 process_scheduled_works+0xb5d/0x1860 kernel/workqueue.c:3397
 worker_thread+0xa53/0xfc0 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>