[syzbot] [kernel?] WARNING: bad unlock balance in copy_process

[syzbot <syzbot+80cb3cc5c14fad191a10@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    785cdec46e92 Merge tag 'x86-core-2025-05-25' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=132bbdf4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=628e87e3a98ec1c4
dashboard link: https://syzkaller.appspot.com/bug?extid=80cb3cc5c14fad191a10
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-785cdec4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/259338148f62/vmlinux-785cdec4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/436abe9bf6f7/bzImage-785cdec4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+80cb3cc5c14fad191a10@syzkaller.appspotmail.com

=====================================
WARNING: bad unlock balance detected!
6.15.0-syzkaller-01958-g785cdec46e92 #0 Not tainted
-------------------------------------
syz.1.441/7809 is trying to release lock (&sighand->siglock) at:
[<ffffffff817a389e>] spin_unlock include/linux/spinlock.h:391 [inline]
[<ffffffff817a389e>] copy_process+0x5d6e/0x9170 kernel/fork.c:2686
but there are no more locks to release!

other info that might help us debug this:
1 lock held by syz.1.441/7809:
 #0: ffffffff8e41c350 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: copy_process+0x3de8/0x9170 kernel/fork.c:2528

stack backtrace:
CPU: 0 UID: 0 PID: 7809 Comm: syz.1.441 Not tainted 6.15.0-syzkaller-01958-g785cdec46e92 #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_unlock_imbalance_bug kernel/locking/lockdep.c:5301 [inline]
 print_unlock_imbalance_bug+0x11b/0x130 kernel/locking/lockdep.c:5275
 __lock_release kernel/locking/lockdep.c:5540 [inline]
 lock_release+0x242/0x2f0 kernel/locking/lockdep.c:5892
 __raw_spin_unlock include/linux/spinlock_api_smp.h:141 [inline]
 _raw_spin_unlock+0x16/0x50 kernel/locking/spinlock.c:186
 spin_unlock include/linux/spinlock.h:391 [inline]
 copy_process+0x5d6e/0x9170 kernel/fork.c:2686
 kernel_clone+0xfc/0x960 kernel/fork.c:2859
 __do_sys_clone3+0x212/0x290 kernel/fork.c:3163
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6443fc31c9
Code: bf 08 00 48 8d 3d dc bf 08 00 e8 e2 28 f6 ff 66 90 b8 ea ff ff ff 48 85 ff 74 2c 48 85 d2 74 27 49 89 c8 b8 b3 01 00 00 0f 05 <48> 85 c0 7c 18 74 01 c3 31 ed 48 83 e4 f0 4c 89 c7 ff d2 48 89 c7
RSP: 002b:00007ffeb834dbb8 EFLAGS: 00000202 ORIG_RAX: 00000000000001b3
RAX: ffffffffffffffda RBX: 00007f6443f455b0 RCX: 00007f6443fc31c9
RDX: 00007f6443f455b0 RSI: 0000000000000058 RDI: 00007ffeb834dc00
RBP: 00007f6444dee6c0 R08: 00007f6444dee6c0 R09: 00007ffeb834dce7
R10: 0000000000000008 R11: 0000000000000202 R12: ffffffffffffffa8
R13: 000000000000000b R14: 00007ffeb834dc00 R15: 00007ffeb834dce8
 </TASK>
------------[ cut here ]------------
pvqspinlock: lock 0xffff8880245e8940 has corrupted value 0x0!
WARNING: CPU: 0 PID: 7809 at kernel/locking/qspinlock_paravirt.h:504 __pv_queued_spin_unlock_slowpath+0x237/0x330 kernel/locking/qspinlock_paravirt.h:504
Modules linked in:
CPU: 0 UID: 0 PID: 7809 Comm: syz.1.441 Not tainted 6.15.0-syzkaller-01958-g785cdec46e92 #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:__pv_queued_spin_unlock_slowpath+0x237/0x330 kernel/locking/qspinlock_paravirt.h:504
Code: 03 0f b6 14 02 4c 89 e8 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 67 41 8b 55 00 4c 89 ee 48 c7 c7 a0 79 8d 8b e8 ba e4 02 f6 90 <0f> 0b 90 90 e9 64 ff ff ff 90 0f 0b 48 89 df 4c 89 04 24 e8 31 e6
RSP: 0018:ffffc900034478d8 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffff8880245e8940 RCX: ffffffff817a98c8
RDX: ffff8880247b0000 RSI: ffffffff817a98d5 RDI: 0000000000000001
RBP: ffff8880245e8948 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 6c6e697073717670 R12: ffff8880245e8950
R13: ffff8880245e8940 R14: 00000000fffffff4 R15: ffffc90003447d60
FS:  000055557a112500(0000) GS:ffff8880d69a6000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c2dcf78 CR3: 000000003467f000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 __raw_callee_save___pv_queued_spin_unlock_slowpath+0x15/0x30
 .slowpath+0x9/0x18
 pv_queued_spin_unlock arch/x86/include/asm/paravirt.h:562 [inline]
 queued_spin_unlock arch/x86/include/asm/qspinlock.h:57 [inline]
 do_raw_spin_unlock+0x172/0x230 kernel/locking/spinlock_debug.c:142
 __raw_spin_unlock include/linux/spinlock_api_smp.h:142 [inline]
 _raw_spin_unlock+0x1e/0x50 kernel/locking/spinlock.c:186
 spin_unlock include/linux/spinlock.h:391 [inline]
 copy_process+0x5d6e/0x9170 kernel/fork.c:2686
 kernel_clone+0xfc/0x960 kernel/fork.c:2859
 __do_sys_clone3+0x212/0x290 kernel/fork.c:3163
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6443fc31c9
Code: bf 08 00 48 8d 3d dc bf 08 00 e8 e2 28 f6 ff 66 90 b8 ea ff ff ff 48 85 ff 74 2c 48 85 d2 74 27 49 89 c8 b8 b3 01 00 00 0f 05 <48> 85 c0 7c 18 74 01 c3 31 ed 48 83 e4 f0 4c 89 c7 ff d2 48 89 c7
RSP: 002b:00007ffeb834dbb8 EFLAGS: 00000202 ORIG_RAX: 00000000000001b3
RAX: ffffffffffffffda RBX: 00007f6443f455b0 RCX: 00007f6443fc31c9
RDX: 00007f6443f455b0 RSI: 0000000000000058 RDI: 00007ffeb834dc00
RBP: 00007f6444dee6c0 R08: 00007f6444dee6c0 R09: 00007ffeb834dce7
R10: 0000000000000008 R11: 0000000000000202 R12: ffffffffffffffa8
R13: 000000000000000b R14: 00007ffeb834dc00 R15: 00007ffeb834dce8
 </TASK>


---
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