watchdog: BUG: soft lockup - CPU#0 stuck for 144s! [syz.4.3993:10026]
CPU#0 Utilization every 22s during lockup:
#1: 98% system, 1% softirq, 1% hardirq, 0% idle
#2: 99% system, 1% softirq, 1% hardirq, 0% idle
#3: 99% system, 1% softirq, 1% hardirq, 0% idle
#4: 100% system, 1% softirq, 1% hardirq, 0% idle
#5: 100% system, 1% softirq, 1% hardirq, 0% idle
Modules linked in:
CPU: 0 UID: 0 PID: 10026 Comm: syz.4.3993 Not tainted syzkaller #0 eb3ac94483332de1dcdde2e475b5ff9bbded7b99
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
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 17 11 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:ffffc9000276f9c0 EFLAGS: 00000283
RAX: 1ffff1102b560d1c RBX: ffffffffffffff28 RCX: dffffc0000000000
RDX: ffffc90003deb000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: ffffc9000276fa10 R08: ffff88812a0f42ef R09: 0000000000000000
R10: ffff88812a0f42e0 R11: ffffed102541e85e R12: ffff88815ab068c0
R13: ffff888131061220 R14: ffff88815ab068e0 R15: ffff8881418a4c40
FS: 00007f9d92a6e6c0(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f27aa5e96c0 CR3: 0000000115c98000 CR4: 00000000003526b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000041391c33
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
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: 0033:0x7f9d91b9bf79
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:00007f9d92a6e028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f9d91e16180 RCX: 00007f9d91b9bf79
RDX: 0000000000000000 RSI: 0000200000000200 RDI: 0000200000000000
RBP: 00007f9d91c327e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000101091 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9d91e16218 R14: 00007f9d91e16180 R15: 00007ffc2c8f6d68
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 10101 Comm: syz.5.4025 Not tainted syzkaller #0 eb3ac94483332de1dcdde2e475b5ff9bbded7b99
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:106
Code: cc cc cc cc cc cc cc b8 2a cb 61 df 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d d3 9c 48 00 55 48 89 e5 fb f4 <5d> c3 cc cc cc cc cc cc cc cc cc cc cc b8 00 00 00 00 90 90 90 90
RSP: 0018:ffffc900012c7930 EFLAGS: 000002d3
RAX: ffffffff814428e1 RBX: 0000000000000003 RCX: ffff88815ad6cc00
RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000000000003
RBP: ffffc900012c7930 R08: ffffffff8740d604 R09: 1ffffffff0e81ac0
R10: dffffc0000000000 R11: fffffbfff0e81ac1 R12: dffffc0000000000
R13: 0000000000000200 R14: 0000000000000003 R15: 1ffff92000258f28
FS: 0000000000000000(0000) GS:ffff8881f6f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6ef7de96c0 CR3: 00000000074a8000 CR4: 00000000003526b0
DR0: 0000000000000000 DR1: 0000000000006800 DR2: 0000000000009951
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
arch_safe_halt arch/x86/include/asm/paravirt.h:112 [inline]
kvm_wait+0x1c6/0x230 arch/x86/kernel/kvm.c:1081
pv_wait arch/x86/include/asm/paravirt.h:596 [inline]
pv_wait_head_or_lock kernel/locking/qspinlock_paravirt.h:466 [inline]
__pv_queued_spin_lock_slowpath+0x8e0/0xe90 kernel/locking/qspinlock.c:508
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+0x115/0x120 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:225 [inline]
mntput_no_expire+0x157/0x6d0 fs/namespace.c:1421
mntput+0x63/0xd0 fs/namespace.c:1476
path_put+0x5b/0x70 fs/namei.c:569
free_fs_struct fs/fs_struct.c:90 [inline]
exit_fs+0xe8/0x160 fs/fs_struct.c:108
do_exit+0x9b4/0x2650 kernel/exit.c:949
do_group_exit+0x229/0x2f0 kernel/exit.c:1095
__do_sys_exit_group kernel/exit.c:1106 [inline]
__se_sys_exit_group kernel/exit.c:1104 [inline]
__x64_sys_exit_group+0x43/0x50 kernel/exit.c:1104
x64_sys_call+0x2ed2/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:232
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: 0033:0x7f6ef7d9bf79
Code: Unable to access opcode bytes at 0x7f6ef7d9bf4f.
RSP: 002b:00007ffddffb7ae8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f6ef7d9bf79
RDX: 00007f6ef6ff9000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007ffddffb7b4c R08: 0000000000000000 R09: 00000000000927c0
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000000000d6
R13: 00000000000927c0 R14: 0000000000043a93 R15: 00007ffddffb7ba0