syzbot

INFO: task kworker/1:0:31 blocked for more than 122 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/1:0     state:D stack:0     pid:31    tgid:31    ppid:2      flags:0x00004000
Workqueue: usb_hub_wq hub_event
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5996 [inline]
 __schedule+0x134f/0x1ea0 kernel/sched/core.c:7843
 __schedule_loop kernel/sched/core.c:7924 [inline]
 schedule+0xc5/0x240 kernel/sched/core.c:7939
 schedule_timeout+0xc7/0x3b0 kernel/time/timer.c:2596
 do_wait_for_common kernel/sched/completion.c:95 [inline]
 __wait_for_common kernel/sched/completion.c:116 [inline]
 wait_for_common+0x369/0x650 kernel/sched/completion.c:127
 wait_for_completion+0x1c/0x40 kernel/sched/completion.c:148
 devtmpfs_submit_req drivers/base/devtmpfs.c:107 [inline]
 devtmpfs_delete_node+0x16d/0x200 drivers/base/devtmpfs.c:156
 device_del+0x2d2/0xd00 drivers/base/core.c:3860
 usb_disconnect+0x60f/0x930 drivers/usb/core/hub.c:2384
 hub_port_connect drivers/usb/core/hub.c:5414 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5714 [inline]
 port_event drivers/usb/core/hub.c:5878 [inline]
 hub_event+0x1c7a/0x4700 drivers/usb/core/hub.c:5960
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x7d4/0x1020 kernel/workqueue.c:3319
 worker_thread+0xc70/0x10b0 kernel/workqueue.c:3400
 kthread+0x2c9/0x370 kernel/kthread.c:389
 ret_from_fork+0x67/0xa0 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 37 Comm: khungtaskd Not tainted syzkaller #0 0044b833cf02edb59ee897eae4c42c13324c9de7
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:94
 dump_stack_lvl+0x140/0x1c0 lib/dump_stack.c:120
 dump_stack+0x19/0x20 lib/dump_stack.c:129
 nmi_cpu_backtrace+0x2ba/0x2d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x142/0x2c0 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:41
 trigger_all_cpu_backtrace include/linux/nmi.h:158 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:267 [inline]
 watchdog+0xdad/0xf00 kernel/hung_task.c:423
 kthread+0x2c9/0x370 kernel/kthread.c:389
 ret_from_fork+0x67/0xa0 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 1321 Comm: syz.2.345 Not tainted syzkaller #0 0044b833cf02edb59ee897eae4c42c13324c9de7
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:next_peer fs/pnode.c:19 [inline]
RIP: 0010:do_make_slave fs/pnode.c:100 [inline]
RIP: 0010:change_mnt_propagation+0x112/0xb00 fs/pnode.c:128
Code: 24 20 4c 89 f0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 74 08 4c 89 f7 e8 f7 10 e7 ff 4d 39 2e 0f 84 8f 00 00 00 <49> 81 c4 d8 00 00 00 4c 89 e0 48 c1 e8 03 48 b9 00 00 00 00 00 fc
RSP: 0018:ffffc9000e7b79c0 EFLAGS: 00000202
RAX: 1ffff1102751eb14 RBX: ffffffffffffff28 RCX: dffffc0000000000
RDX: ffffc90002a06000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: ffffc9000e7b7a10 R08: ffff888114c3082f R09: 0000000000000000
R10: ffff888114c30820 R11: ffffed1022986106 R12: ffff88813a8f5880
R13: ffff88812cf6dee0 R14: ffff88813a8f58a0 R15: ffff88813be90fc0
FS:  00007ffa9b57a6c0(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffa991d5ff8 CR3: 0000000116e64000 CR4: 00000000003526b0
Call Trace:
 <TASK>
 umount_tree+0xe16/0xf90 fs/namespace.c:1813
 attach_recursive_mnt+0x6e7/0x2210 fs/namespace.c:2569
 graft_tree+0x157/0x1c0 fs/namespace.c:2704
 do_loopback+0x36a/0x4c0 fs/namespace.c:2836
 path_mount+0x56b/0x1010 fs/namespace.c:3878
 do_mount fs/namespace.c:3897 [inline]
 __do_sys_mount fs/namespace.c:4107 [inline]
 __se_sys_mount+0x2bf/0x480 fs/namespace.c:4084
 __x64_sys_mount+0xc3/0xf0 fs/namespace.c:4084
 x64_sys_call+0x2021/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/common.c:47 [inline]
 do_syscall_64+0x57/0xf0 arch/x86/entry/common.c:78
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7ffa9a79aeb9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffa9b57a028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffa9aa15fa0 RCX: 00007ffa9a79aeb9
RDX: 0000000000000000 RSI: 0000200000000200 RDI: 0000200000000380
RBP: 00007ffa9a808c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000002125099 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffa9aa16038 R14: 00007ffa9aa15fa0 R15: 00007ffe0b71bdf8
 </TASK>