[syzbot] [bcachefs?] general protection fault in bch2_subvolume_delete

[syzbot <syzbot+2875f6362e0214a32381@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    c4b9570cfb63 Merge tag 'audit-pr-20250121' of git://git.ke..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=120c1824580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5d46425e33fe266e
dashboard link: https://syzkaller.appspot.com/bug?extid=2875f6362e0214a32381
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=125c3618580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11de5964580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7feb34a89c2a/non_bootable_disk-c4b9570c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/731d6adef14e/vmlinux-c4b9570c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fba145e47ede/bzImage-c4b9570c.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/875e2f608701/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2875f6362e0214a32381@syzkaller.appspotmail.com

bcachefs (loop0): scanning for missing backpointers in 4/128 buckets
 done
bcachefs (loop0): reconstruct_snapshots... done
bcachefs (loop0): check_subvols...
subvolume 1 points to missing subvolume root 4096:4294967295, fixing
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 UID: 0 PID: 5303 Comm: syz-executor216 Not tainted 6.13.0-syzkaller-02526-gc4b9570cfb63 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:__bch2_subvolume_delete fs/bcachefs/subvolume.c:444 [inline]
RIP: 0010:bch2_subvolume_delete+0x24bc/0x3bb0 fs/bcachefs/subvolume.c:468
Code: 89 ef 48 8d b4 24 40 04 00 00 e8 bf 41 cc ff 4d 85 ff 75 9d e8 15 d9 49 fd 4c 89 e0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <0f> b6 04 08 84 c0 0f 85 63 12 00 00 45 8b 34 24 44 89 f7 8b 5c 24
RSP: 0018:ffffc9000d0be760 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 00000000fffff799 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffc9000d0bebae
RBP: ffffc9000d0bee30 R08: ffffc9000d0bebad R09: 0000000000000000
R10: ffffc9000d0beba0 R11: fffff52001a17d76 R12: 0000000000000000
R13: ffff88804351c000 R14: 0000000000000000 R15: fffffffffffff799
FS:  000055557ca05380(0000) GS:ffff88801fc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000565245a9fa40 CR3: 000000003407e000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 check_subvol fs/bcachefs/subvolume.c:115 [inline]
 bch2_check_subvols+0x1cac/0x3d80 fs/bcachefs/subvolume.c:163
 bch2_run_recovery_pass+0xf0/0x1e0 fs/bcachefs/recovery_passes.c:226
 bch2_run_recovery_passes+0x2ad/0xa90 fs/bcachefs/recovery_passes.c:291
 bch2_fs_recovery+0x265a/0x3de0 fs/bcachefs/recovery.c:937
 bch2_fs_start+0x37c/0x610 fs/bcachefs/super.c:1030
 bch2_fs_get_tree+0xd8d/0x1740 fs/bcachefs/fs.c:2203
 vfs_get_tree+0x90/0x2b0 fs/super.c:1814
 do_new_mount+0x2be/0xb40 fs/namespace.c:3560
 do_mount fs/namespace.c:3900 [inline]
 __do_sys_mount fs/namespace.c:4111 [inline]
 __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4088
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f95e107326a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 5e 04 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffde9323ca8 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffde9323cc0 RCX: 00007f95e107326a
RDX: 00000000200058c0 RSI: 0000000020005900 RDI: 00007ffde9323cc0
RBP: 0000000000000004 R08: 00007ffde9323d00 R09: 00000000000058fc
R10: 0000000001000000 R11: 0000000000000282 R12: 0000000001000000
R13: 00007ffde9323d00 R14: 0000000000000003 R15: 0000000001000000
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__bch2_subvolume_delete fs/bcachefs/subvolume.c:444 [inline]
RIP: 0010:bch2_subvolume_delete+0x24bc/0x3bb0 fs/bcachefs/subvolume.c:468
Code: 89 ef 48 8d b4 24 40 04 00 00 e8 bf 41 cc ff 4d 85 ff 75 9d e8 15 d9 49 fd 4c 89 e0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <0f> b6 04 08 84 c0 0f 85 63 12 00 00 45 8b 34 24 44 89 f7 8b 5c 24
RSP: 0018:ffffc9000d0be760 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 00000000fffff799 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffc9000d0bebae
RBP: ffffc9000d0bee30 R08: ffffc9000d0bebad R09: 0000000000000000
R10: ffffc9000d0beba0 R11: fffff52001a17d76 R12: 0000000000000000
R13: ffff88804351c000 R14: 0000000000000000 R15: fffffffffffff799
FS:  000055557ca05380(0000) GS:ffff88801fc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005621c7fab0f8 CR3: 000000003407e000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	89 ef                	mov    %ebp,%edi
   2:	48 8d b4 24 40 04 00 	lea    0x440(%rsp),%rsi
   9:	00
   a:	e8 bf 41 cc ff       	call   0xffcc41ce
   f:	4d 85 ff             	test   %r15,%r15
  12:	75 9d                	jne    0xffffffb1
  14:	e8 15 d9 49 fd       	call   0xfd49d92e
  19:	4c 89 e0             	mov    %r12,%rax
  1c:	48 c1 e8 03          	shr    $0x3,%rax
  20:	48 b9 00 00 00 00 00 	movabs $0xdffffc0000000000,%rcx
  27:	fc ff df
* 2a:	0f b6 04 08          	movzbl (%rax,%rcx,1),%eax <-- trapping instruction
  2e:	84 c0                	test   %al,%al
  30:	0f 85 63 12 00 00    	jne    0x1299
  36:	45 8b 34 24          	mov    (%r12),%r14d
  3a:	44 89 f7             	mov    %r14d,%edi
  3d:	8b                   	.byte 0x8b
  3e:	5c                   	pop    %rsp
  3f:	24                   	.byte 0x24


---
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