[syzbot] [btrfs?] kernel BUG in btrfs_qgroup_inherit

[syzbot <syzbot+b44d4a4885bc82af2a06@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    416f99c3b16f Merge tag 'driver-core-6.19-rc1' of git://git..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12ed421a580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f5a0bcda07a0bfd7
dashboard link: https://syzkaller.appspot.com/bug?extid=b44d4a4885bc82af2a06
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12770eb4580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=148bbc1a580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-416f99c3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/fb10fdbc0d42/vmlinux-416f99c3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f277b82f7dd0/bzImage-416f99c3.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/11aaebf70e5c/mount_0.gz
  fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=176f4992580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b44d4a4885bc82af2a06@syzkaller.appspotmail.com

R13: 00007f24f59e5fa0 R14: 00007f24f59e5fa0 R15: 0000000000000003
 </TASK>
assertion failed: prealloc == NULL :: 0, in fs/btrfs/qgroup.c:3529
------------[ cut here ]------------
kernel BUG at fs/btrfs/qgroup.c:3529!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5562 Comm: syz.0.19 Not tainted syzkaller #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:btrfs_qgroup_inherit+0x2892/0x28a0 fs/btrfs/qgroup.c:3529
Code: ff ff e8 d1 1f d4 fd 48 c7 c7 a0 e5 b0 8b 48 c7 c6 00 e6 b0 8b 31 d2 48 c7 c1 20 e2 b0 8b 41 b8 c9 0d 00 00 e8 ef 58 3a fd 90 <0f> 0b 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90
RSP: 0018:ffffc9000cbe7740 EFLAGS: 00010246
RAX: 0000000000000042 RBX: 0000000000000000 RCX: b3bb6c739819f900
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: ffffc9000cbe7990 R08: ffffc9000cbe7467 R09: 1ffff9200197ce8c
R10: dffffc0000000000 R11: fffff5200197ce8d R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 00000000fffffff4
FS:  0000555588ca7500(0000) GS:ffff88808d679000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b31b63fff CR3: 0000000011fab000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 create_subvol+0x5ad/0x18f0 fs/btrfs/ioctl.c:570
 btrfs_mksubvol+0x6e4/0x12c0 fs/btrfs/ioctl.c:928
 __btrfs_ioctl_snap_create+0x2b2/0x730 fs/btrfs/ioctl.c:1201
 btrfs_ioctl_snap_create+0x131/0x180 fs/btrfs/ioctl.c:1259
 btrfs_ioctl+0xb4d/0xd00 fs/btrfs/ioctl.c:-1
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f24f578f7c9
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:00007ffc9b4adc18 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f24f59e5fa0 RCX: 00007f24f578f7c9
RDX: 0000200000000280 RSI: 000000005000940e RDI: 0000000000000003
RBP: 00007ffc9b4adc70 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00007f24f59e5fa0 R14: 00007f24f59e5fa0 R15: 0000000000000003
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:btrfs_qgroup_inherit+0x2892/0x28a0 fs/btrfs/qgroup.c:3529
Code: ff ff e8 d1 1f d4 fd 48 c7 c7 a0 e5 b0 8b 48 c7 c6 00 e6 b0 8b 31 d2 48 c7 c1 20 e2 b0 8b 41 b8 c9 0d 00 00 e8 ef 58 3a fd 90 <0f> 0b 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90
RSP: 0018:ffffc9000cbe7740 EFLAGS: 00010246
RAX: 0000000000000042 RBX: 0000000000000000 RCX: b3bb6c739819f900
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: ffffc9000cbe7990 R08: ffffc9000cbe7467 R09: 1ffff9200197ce8c
R10: dffffc0000000000 R11: fffff5200197ce8d R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 00000000fffffff4
FS:  0000555588ca7500(0000) GS:ffff88808d679000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b31b63fff CR3: 0000000011fab000 CR4: 0000000000352ef0


---
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