[syzbot] [ocfs2?] kernel BUG in ocfs2_block_group_search

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dbf8fe85a16a Merge tag 'net-6.19-rc4' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16b19792580000
kernel config: https://syzkaller.appspot.com/x/.config?x=513255d80ab78f2b
dashboard link: https://syzkaller.appspot.com/bug?extid=44c564a3cb08605f34a1
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=10ef2422580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11b19792580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-dbf8fe85.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/86d0a4a4173a/vmlinux-dbf8fe85.xz
kernel image: https://storage.googleapis.com/syzbot-assets/23bd847a572d/bzImage-dbf8fe85.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/97470b986566/mount_0.gz
fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=1047329a580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+44c564...@syzkaller.appspotmail.com

=======================================================
JBD2: Ignoring recovery information on journal
ocfs2: Mounting device (7,0) on (node local, slot 0) with ordered data mode.
------------[ cut here ]------------
kernel BUG at fs/ocfs2/suballoc.c:1611!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5527 Comm: syz.0.17 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:ocfs2_block_group_search+0x367/0x490 fs/ocfs2/suballoc.c:1611
Code: d9 80 e1 07 80 c1 03 38 c1 0f 8c c5 fe ff ff 48 89 df e8 0c 40 77 fe e9 b8 fe ff ff e8 92 95 0f fe 90 0f 0b e8 8a 95 0f fe 90 <0f> 0b f3 0f 1e fa 65 44 8b 3d 4f 2e cf 0e bf 07 00 00 00 44 89 fe
RSP: 0018:ffffc90002616bb8 EFLAGS: 00010293
RAX: ffffffff83b171d6 RBX: 000000000000004a RCX: ffff888000b70000
RDX: 0000000000000000 RSI: 000000000000004a RDI: 000000000000004a
RBP: 0000000000000001 R08: 00000000ffffffff R09: ffffc900026171a0
R10: dffffc0000000000 R11: ffffffff83b16e70 R12: ffff8880470b0740
R13: ffff88804453c740 R14: ffff8880230d7000 R15: 000000000000004a
FS: 000055556aa08500(0000) GS:ffff88808d416000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbdcf97f000 CR3: 00000000113be000 CR4: 0000000000352ef0
Call Trace:
<TASK>
ocfs2_search_chain+0x5f3/0x1d60 fs/ocfs2/suballoc.c:1836
ocfs2_claim_suballoc_bits+0xc1e/0x1f60 fs/ocfs2/suballoc.c:2011
ocfs2_claim_new_inode+0x332/0x7a0 fs/ocfs2/suballoc.c:2303
ocfs2_mknod_locked+0x100/0x250 fs/ocfs2/namei.c:638
ocfs2_mknod+0x10a5/0x2030 fs/ocfs2/namei.c:385
ocfs2_create+0x195/0x420 fs/ocfs2/namei.c:677
lookup_open fs/namei.c:4440 [inline]
open_last_lookups fs/namei.c:4540 [inline]
path_openat+0x18bb/0x3dd0 fs/namei.c:4784
do_filp_open+0x1fa/0x410 fs/namei.c:4814
do_sys_openat2+0x121/0x200 fs/open.c:1430
do_sys_open fs/open.c:1436 [inline]
__do_sys_openat fs/open.c:1452 [inline]
__se_sys_openat fs/open.c:1447 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1447
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe1e2d8f7c9
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:00007fff02afc7a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fe1e2fe5fa0 RCX: 00007fe1e2d8f7c9
RDX: 000000000000275a RSI: 0000200000000040 RDI: ffffffffffffff9c
RBP: 00007fe1e2e13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe1e2fe5fa0 R14: 00007fe1e2fe5fa0 R15: 0000000000000004
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:ocfs2_block_group_search+0x367/0x490 fs/ocfs2/suballoc.c:1611
Code: d9 80 e1 07 80 c1 03 38 c1 0f 8c c5 fe ff ff 48 89 df e8 0c 40 77 fe e9 b8 fe ff ff e8 92 95 0f fe 90 0f 0b e8 8a 95 0f fe 90 <0f> 0b f3 0f 1e fa 65 44 8b 3d 4f 2e cf 0e bf 07 00 00 00 44 89 fe
RSP: 0018:ffffc90002616bb8 EFLAGS: 00010293
RAX: ffffffff83b171d6 RBX: 000000000000004a RCX: ffff888000b70000
RDX: 0000000000000000 RSI: 000000000000004a RDI: 000000000000004a
RBP: 0000000000000001 R08: 00000000ffffffff R09: ffffc900026171a0
R10: dffffc0000000000 R11: ffffffff83b16e70 R12: ffff8880470b0740
R13: ffff88804453c740 R14: ffff8880230d7000 R15: 000000000000004a
FS: 000055556aa08500(0000) GS:ffff88808d416000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd8f777e286 CR3: 00000000113be000 CR4: 0000000000352ef0


---
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***

Subject: [PATCH] ocfs2: validate allocator type to prevent BUG_ON in ocfs2_block_group_search
Author: karti...@gmail.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

A corrupted filesystem image can have an inode allocator with the
OCFS2_BITMAP_FL flag incorrectly set, making ocfs2_is_cluster_bitmap()
return true. When the code later calls ocfs2_block_group_search(),
it triggers BUG_ON(ocfs2_is_cluster_bitmap(inode)) causing a kernel panic.

Call trace:
ocfs2_block_group_search+0x1c7/0x2c0 fs/ocfs2/suballoc.c:1611
ocfs2_search_chain+0x38a/0x1010 fs/ocfs2/suballoc.c:1764
ocfs2_claim_suballoc_bits+0x3a4/0x650 fs/ocfs2/suballoc.c:1978
ocfs2_claim_new_inode+0x95/0x130 fs/ocfs2/suballoc.c:2137
ocfs2_mknod_locked+0x129/0x510 fs/ocfs2/namei.c:568
ocfs2_mknod+0x5c7/0x11d0 fs/ocfs2/namei.c:802
ocfs2_create+0x136/0x170 fs/ocfs2/namei.c:852

Add validation in ocfs2_reserve_suballoc_bits() to check that the
allocator inode type matches the expected type:
- Global bitmap allocator must have OCFS2_BITMAP_FL flag set
- Other allocators (inode, extent) must NOT have OCFS2_BITMAP_FL set

This follows the existing pattern of validating OCFS2_CHAIN_FL in the
same function and uses ocfs2_error() for graceful error handling.

Reported-by: syzbot+44c564...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=44c564a3cb08605f34a1
Signed-off-by: Deepanshu Kartikey <karti...@gmail.com>
---
fs/ocfs2/suballoc.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)

diff --git a/fs/ocfs2/suballoc.c b/fs/ocfs2/suballoc.c
index 8e6e5235b30c..fb72c062a8d5 100644
--- a/fs/ocfs2/suballoc.c
+++ b/fs/ocfs2/suballoc.c
@@ -813,6 +813,26 @@ static int ocfs2_reserve_suballoc_bits(struct ocfs2_super *osb,
goto bail;
}

+ /*
+ * Validate allocator type matches expected bitmap type.
+ * Global bitmap must have BITMAP flag, other allocators must not.
+ * This prevents a corrupted filesystem from triggering BUG_ON
+ * in ocfs2_block_group_search() or ocfs2_cluster_group_search().
+ */
+ if (type == GLOBAL_BITMAP_SYSTEM_INODE) {
+ if (!ocfs2_is_cluster_bitmap(alloc_inode)) {
+ status = ocfs2_error(alloc_inode->i_sb,
+ "Global bitmap %llu missing bitmap flag\n",
+ (unsigned long long)le64_to_cpu(fe->i_blkno));
+ goto bail;
+ }
+ } else if (ocfs2_is_cluster_bitmap(alloc_inode)) {
+ status = ocfs2_error(alloc_inode->i_sb,
+ "Allocator %llu has invalid bitmap flag\n",
+ (unsigned long long)le64_to_cpu(fe->i_blkno));
+ goto bail;
+ }
+
free_bits = le32_to_cpu(fe->id1.bitmap1.i_total) -
le32_to_cpu(fe->id1.bitmap1.i_used);

--
2.43.0

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+44c564...@syzkaller.appspotmail.com
Tested-by: syzbot+44c564...@syzkaller.appspotmail.com

Tested on:

commit: aacb0a6d Merge tag 'pmdomain-v6.19-rc3' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13aec69a580000

kernel config: https://syzkaller.appspot.com/x/.config?x=513255d80ab78f2b
dashboard link: https://syzkaller.appspot.com/bug?extid=44c564a3cb08605f34a1
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

patch: https://syzkaller.appspot.com/x/patch.diff?x=10710074580000

Note: testing is done by a robot and is best-effort only.