Re: [syzbot] [bcachefs?] UBSAN: array-index-out-of-bounds in bch2_accounting_validate

syzbot
2025-08-04T12:19:07Z

> On Aug 4, 2025, at 15:18, syzbot <syzbot+cd063f869beedf5b9cd7@syzkaller.appspotmail.com> wrote:
>>
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit: 352af6a011d5 Merge tag 'rust-6.17' of git://git.kernel.org..
>> git tree: upstream
>> console+strace: https://syzkaller.appspot.com/x/log.txt?x=135d7aa2580000
>> kernel config: https://syzkaller.appspot.com/x/.config?x=cae1291240e8962a
>> dashboard link: https://syzkaller.appspot.com/bug?extid=cd063f869beedf5b9cd7
>> compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14dcc6a2580000
>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=133e02f0580000
>>
>> Downloadable assets:
>> disk image: https://storage.googleapis.com/syzbot-assets/a762497d1fce/disk-352af6a0.raw.xz
>> vmlinux: https://storage.googleapis.com/syzbot-assets/3055e1e47995/vmlinux-352af6a0.xz
>> kernel image: https://storage.googleapis.com/syzbot-assets/aa300ee98202/bzImage-352af6a0.xz
>> mounted in repro: https://storage.googleapis.com/syzbot-assets/de2a4b00a48a/mount_0.gz
>>
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+cd063f869beedf5b9cd7@syzkaller.appspotmail.com
>>
>> bcachefs (loop0): error reading btree root btree=subvolumes level=0: btree_node_read_error, fixing
>> bcachefs (loop0): invalid bkey in btree_node btree=snapshot_trees level=0: u64s 6 type snapshot_tree POS_MIN len 0 ver 0: subvol 1 root snapshot 4294967295
>> bad pos, deleting
>> bcachefs (loop0): error reading btree root btree=snapshot_trees level=0: btree_node_read_error, fixing
>> ------------[ cut here ]------------
>> UBSAN: array-index-out-of-bounds in fs/bcachefs/disk_accounting.c:238:2
>> index 175 is out of range for type 'const unsigned int[9]'
>> CPU: 0 UID: 0 PID: 5849 Comm: syz-executor427 Tainted: G W 6.16.0-syzkaller-11322-g352af6a011d5 #0 PREEMPT_{RT,(full)}
>> Tainted: [W]=WARN
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
>> Call Trace:
>> <TASK>
>> dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
>> ubsan_epilogue+0xa/0x40 lib/ubsan.c:233
>> __ubsan_handle_out_of_bounds+0xe9/0xf0 lib/ubsan.c:455
>> bch2_accounting_validate+0x112f/0x1400 fs/bcachefs/disk_accounting.c:238
>> bch2_bkey_val_validate+0x202/0x3e0 fs/bcachefs/bkey_methods.c:143
>> btree_node_bkey_val_validate fs/bcachefs/btree_io.c:880 [inline]
>> bch2_btree_node_read_done+0x4051/0x5550 fs/bcachefs/btree_io.c:1303
>> btree_node_read_work+0x40e/0xe60 fs/bcachefs/btree_io.c:1440
>> bch2_btree_node_read+0x887/0x2a00 fs/bcachefs/btree_io.c:-1
>> __bch2_btree_root_read fs/bcachefs/btree_io.c:1906 [inline]
>> bch2_btree_root_read+0x5f0/0x760 fs/bcachefs/btree_io.c:1928
>> read_btree_roots+0x2c6/0x840 fs/bcachefs/recovery.c:615
>> bch2_fs_recovery+0x261f/0x3a50 fs/bcachefs/recovery.c:1006
>> bch2_fs_start+0xaaf/0xda0 fs/bcachefs/super.c:1213
>> bch2_fs_get_tree+0xb39/0x1520 fs/bcachefs/fs.c:2488
>> vfs_get_tree+0x92/0x2b0 fs/super.c:1815
>> do_new_mount+0x2a2/0x9e0 fs/namespace.c:3805
>> do_mount fs/namespace.c:4133 [inline]
>> __do_sys_mount fs/namespace.c:4344 [inline]
>> __se_sys_mount+0x317/0x410 fs/namespace.c:4321
>> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>> do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
>> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>> RIP: 0033:0x7f5016bf5eaa
>> 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:00007ffd552f5c58 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5
>> RAX: ffffffffffffffda RBX: 00007ffd552f5c70 RCX: 00007f5016bf5eaa
>> RDX: 0000200000001000 RSI: 0000200000000000 RDI: 00007ffd552f5c70
>> RBP: 0000200000000000 R08: 00007ffd552f5cb0 R09: 000000000000492c
>> R10: 0000000000000000 R11: 0000000000000282 R12: 0000200000001000
>> R13: 00007ffd552f5cb0 R14: 0000000000000003 R15: 0000000000000000
>> </TASK>
>> ---[ end trace ]---
>>
>>
>> ---
>> This report is generated by a bot. It may contain errors.
>> See https://goo.gl/tpsmEJ for more information about syzbot.
>> syzbot engineers can be reached at syzkaller@googlegroups.com.
>>
>> syzbot will keep track of this issue. See:
>> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>>
>> If the report is already addressed, let syzbot know by replying with:
>> #syz fix: exact-commit-title
>>
>> If you want syzbot to run the reproducer, reply with:
>> #syz test: git://repo/address.git branch-or-commit-hash
>> If you attach or paste a git patch, syzbot will apply it before testing.
>>
>> If you want to overwrite report's subsystems, reply with:
>> #syz set subsystems: new-subsystem
>> (See the list of subsystem names on the web dashboard)
>>
>> If the report is a duplicate of another one, reply with:
>> #syz dup: exact-subject-of-another-report
>>
>> If you want to undo deduplication, reply with:
>> #syz undup
>>
>
>
> #syz test:

want either no args or 2 args (repo, branch), got 4

>
> diff --git a/fs/bcachefs/disk_accounting.c b/fs/bcachefs/disk_accounting.c
> index f96530c70262..4f5b290dc8f1 100644
> --- a/fs/bcachefs/disk_accounting.c
> +++ b/fs/bcachefs/disk_accounting.c
> @@ -184,6 +184,11 @@ int bch2_accounting_validate(struct bch_fs *c, struct bkey_s_c k,
> void *end = &acc_k + 1;
> int ret = 0;
>
> + bkey_fsck_err_on(acc_k.type >= BCH_DISK_ACCOUNTING_TYPE_NR,
> + c, accounting_key_type_invalid,
> + "invalid accounting type (%u >= %u)",
> + acc_k.type, BCH_DISK_ACCOUNTING_TYPE_NR);
> +
> bkey_fsck_err_on((from.flags & BCH_VALIDATE_commit) &&
> bversion_zero(k.k->bversion),
> c, accounting_key_version_0,
> diff --git a/fs/bcachefs/sb-errors_format.h b/fs/bcachefs/sb-errors_format.h
> index 5317b1bfe2e5..5ba28a684f51 100644
> --- a/fs/bcachefs/sb-errors_format.h
> +++ b/fs/bcachefs/sb-errors_format.h
> @@ -328,6 +328,7 @@ enum bch_fsck_flags {
> x(accounting_key_replicas_devs_unsorted, 280, FSCK_AUTOFIX) \
> x(accounting_key_version_0, 282, FSCK_AUTOFIX) \
> x(accounting_key_nr_counters_wrong, 307, FSCK_AUTOFIX) \
> + x(accounting_key_type_invalid, 325, FSCK_AUTOFIX) \
> x(logged_op_but_clean, 283, FSCK_AUTOFIX) \
> x(compression_opt_not_marked_in_sb, 295, FSCK_AUTOFIX) \
> x(compression_type_not_marked_in_sb, 296, FSCK_AUTOFIX) \
> @@ -336,7 +337,7 @@ enum bch_fsck_flags {
> x(dirent_stray_data_after_cf_name, 305, 0) \
> x(rebalance_work_incorrectly_set, 309, FSCK_AUTOFIX) \
> x(rebalance_work_incorrectly_unset, 310, FSCK_AUTOFIX) \
> - x(MAX, 325, 0)
> + x(MAX, 326, 0)
>
> enum bch_sb_error_id {
> #define x(t, n, ...) BCH_FSCK_ERR_##t = n,
>