syzbot

watchdog: BUG: soft lockup - CPU#0 stuck for 144s! [syz.5.4306:10650]
CPU#0 Utilization every 22s during lockup:
	#1: 100% system,	  1% softirq,	  1% hardirq,	  0% idle
	#2: 100% system,	  1% softirq,	  1% hardirq,	  0% idle
	#3: 100% system,	  0% softirq,	  1% hardirq,	  0% idle
	#4: 100% system,	  1% softirq,	  1% hardirq,	  0% idle
	#5: 100% system,	  0% softirq,	  1% hardirq,	  0% idle
Modules linked in:
CPU: 0 UID: 0 PID: 10650 Comm: syz.5.4306 Not tainted syzkaller #0 ab9e215a8d79cd87c3adea34e0b2794648952c95
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
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 47 51 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:ffffc9000106f9c0 EFLAGS: 00000202
RAX: 1ffff110250d0adc RBX: ffffffffffffff28 RCX: dffffc0000000000
RDX: ffffc90002e37000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: ffffc9000106fa10 R08: ffff88814fa389ef R09: 0000000000000000
R10: ffff88814fa389e0 R11: ffffed1029f4713e R12: ffff8881286856c0
R13: ffff888110404ee0 R14: ffff8881286856e0 R15: ffff88812057afc0
FS:  00007f5b7a1626c0(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f11ad1a8f98 CR3: 00000001503c4000 CR4: 00000000003526b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000012009800
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 umount_tree+0xdfd/0xf70 fs/namespace.c:1803
 attach_recursive_mnt+0x6df/0x21e0 fs/namespace.c:2549
 graft_tree+0x157/0x1c0 fs/namespace.c:2684
 do_loopback+0x364/0x4b0 fs/namespace.c:2816
 path_mount+0x582/0x1050 fs/namespace.c:3858
 do_mount fs/namespace.c:3877 [inline]
 __do_sys_mount fs/namespace.c:4087 [inline]
 __se_sys_mount+0x2bd/0x480 fs/namespace.c:4064
 __x64_sys_mount+0xc3/0xf0 fs/namespace.c:4064
 x64_sys_call+0x2021/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x58/0xf0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7f5b7938efc9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f5b7a162038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f5b795e5fa0 RCX: 00007f5b7938efc9
RDX: 0000000000000000 RSI: 0000200000000200 RDI: 0000200000000000
RBP: 00007f5b79411f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000101091 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5b795e6038 R14: 00007f5b795e5fa0 R15: 00007ffc90bf5068
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 10680 Comm: syz.4.4318 Not tainted syzkaller #0 ab9e215a8d79cd87c3adea34e0b2794648952c95
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:pv_wait_head_or_lock kernel/locking/qspinlock_paravirt.h:430 [inline]
RIP: 0010:__pv_queued_spin_lock_slowpath+0x697/0xcc0 kernel/locking/qspinlock.c:508
Code: 01 00 00 c6 03 01 bb 00 80 ff ff 66 c7 84 24 90 00 00 00 00 01 48 8b 44 24 28 42 0f b6 04 30 84 c0 75 4c 80 3f 00 74 08 f3 90 <ff> c3 75 dd eb 59 be 02 00 00 00 e8 d9 ed 4c fc 48 8d bc 24 90 00
RSP: 0018:ffffc90004d87ac0 EFLAGS: 00000206
RAX: 0000000000000000 RBX: 00000000fffff477 RCX: ffff88811dd19300
RDX: ffff8881f6f50a54 RSI: 0000000000000003 RDI: ffffffff8720d604
RBP: ffffc90004d87bd0 R08: ffffffff8720d604 R09: 1ffffffff0e41ac0
R10: dffffc0000000000 R11: fffffbfff0e41ac1 R12: 0000000000000000
R13: 1ffffffff0e5cd9d R14: dffffc0000000000 R15: 1ffffffff0e41ac0
FS:  0000555577a29500(0000) GS:ffff8881f6f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f427f61ff98 CR3: 000000011598a000 CR4: 00000000003526b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000012009800
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:584 [inline]
 queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:51 [inline]
 queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
 do_raw_spin_lock include/linux/spinlock.h:187 [inline]
 __raw_spin_lock include/linux/spinlock_api_smp.h:134 [inline]
 _raw_spin_lock+0x109/0x120 kernel/locking/spinlock.c:154
 spin_lock include/linux/spinlock.h:351 [inline]
 write_seqlock include/linux/seqlock.h:876 [inline]
 lock_mount_hash fs/namespace.c:215 [inline]
 mntput_no_expire+0x147/0x6c0 fs/namespace.c:1411
 mntput+0x63/0xd0 fs/namespace.c:1466
 __fput+0x5c5/0xa00 fs/file_table.c:440
 ____fput+0x20/0x30 fs/file_table.c:457
 task_work_run+0x1e0/0x250 kernel/task_work.c:240
 resume_user_mode_work+0x36/0x50 include/linux/resume_user_mode.h:50
 exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x64/0xb0 kernel/entry/common.c:218
 do_syscall_64+0x64/0xf0 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7f11ac38efc9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffec41dd438 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007f11ac5e7da0 RCX: 00007f11ac38efc9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f11ac5e7da0 R08: 0000000000000108 R09: 0000000ec41dd72f
R10: 00007f11ac5e7cb0 R11: 0000000000000246 R12: 0000000000034d07
R13: 00007f11ac5e6090 R14: ffffffffffffffff R15: 00007ffec41dd550
 </TASK>