[v6.6] kernel BUG in ocfs2_claim_suballoc_bits

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syzbot

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Nov 9, 2025, 8:08:33 AM (12 days ago) Nov 9
to syzkaller...@googlegroups.com
Hello,

syzbot found the following issue on:

HEAD commit: 0a805b6ea8cd Linux 6.6.116
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=173d2412580000
kernel config: https://syzkaller.appspot.com/x/.config?x=12606d4b8832c7e4
dashboard link: https://syzkaller.appspot.com/bug?extid=a11ccf24c7d55bec632b
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/13874446b4b2/disk-0a805b6e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/69a5e59e1ade/vmlinux-0a805b6e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/322c0711f976/bzImage-0a805b6e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a11ccf...@syzkaller.appspotmail.com

(syz.8.5926,23680,1):ocfs2_read_blocks_sync:112 ERROR: status = -12
(syz.8.5926,23680,1):update_backups:188 ERROR: status = -12
ocfs2: Failed to update super blocks on 7,8 during fs resize. This condition is not fatal, but fsck.ocfs2 should be run to fix it
------------[ cut here ]------------
kernel BUG at fs/ocfs2/suballoc.c:1349!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 23680 Comm: syz.8.5926 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:ocfs2_block_group_set_bits+0x53e/0x670 fs/ocfs2/suballoc.c:1349
Code: ff 44 89 f9 80 e1 07 fe c1 38 c1 0f 8c 8e fd ff ff 4c 89 ff e8 e3 fa 82 fe e9 81 fd ff ff e8 c9 9f 2b fe 0f 0b e8 c2 9f 2b fe <0f> 0b f3 0f 1e fa 65 44 8b 3d f0 c7 a9 7c bf 07 00 00 00 44 89 fe
RSP: 0018:ffffc900041270c0 EFLAGS: 00010287
RAX: ffffffff8359efce RBX: 0000000000000008 RCX: 0000000000080000
RDX: ffffc900120da000 RSI: 0000000000021d71 RDI: 0000000000021d72
RBP: ffffc900041271b0 R08: 0000000000000000 R09: 0000000000000008
R10: 00000000fffffffc R11: 0000000000000002 R12: dffffc0000000000
R13: 0000000000000000 R14: ffff888043a01000 R15: 0000000000000001
FS: 00007fe3bbdcc6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c342b53 CR3: 000000005fadd000 CR4: 00000000003526e0
Call Trace:
<TASK>
ocfs2_search_one_group fs/ocfs2/suballoc.c:1717 [inline]
ocfs2_claim_suballoc_bits+0x1434/0x2230 fs/ocfs2/suballoc.c:1915
__ocfs2_claim_clusters+0x302/0x900 fs/ocfs2/suballoc.c:2338
ocfs2_add_clusters_in_btree+0x337/0xf60 fs/ocfs2/alloc.c:4827
ocfs2_add_inode_data fs/ocfs2/file.c:550 [inline]
ocfs2_extend_allocation+0x9fd/0x1760 fs/ocfs2/file.c:630
ocfs2_allocate_unwritten_extents+0x2ea/0x7b0 fs/ocfs2/file.c:1495
__ocfs2_change_file_space+0x8d6/0xe40 fs/ocfs2/file.c:2022
ocfs2_fallocate+0x1f5/0x240 fs/ocfs2/file.c:2137
vfs_fallocate+0x58e/0x700 fs/open.c:324
ksys_fallocate fs/open.c:347 [inline]
__do_sys_fallocate fs/open.c:355 [inline]
__se_sys_fallocate fs/open.c:353 [inline]
__x64_sys_fallocate+0xc1/0x110 fs/open.c:353
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fe3baf8f6c9
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:00007fe3bbdcc038 EFLAGS: 00000246 ORIG_RAX: 000000000000011d
RAX: ffffffffffffffda RBX: 00007fe3bb1e5fa0 RCX: 00007fe3baf8f6c9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00007fe3bb011f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000008000c62 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe3bb1e6038 R14: 00007fe3bb1e5fa0 R15: 00007ffe94eb9e88
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:ocfs2_block_group_set_bits+0x53e/0x670 fs/ocfs2/suballoc.c:1349
Code: ff 44 89 f9 80 e1 07 fe c1 38 c1 0f 8c 8e fd ff ff 4c 89 ff e8 e3 fa 82 fe e9 81 fd ff ff e8 c9 9f 2b fe 0f 0b e8 c2 9f 2b fe <0f> 0b f3 0f 1e fa 65 44 8b 3d f0 c7 a9 7c bf 07 00 00 00 44 89 fe
RSP: 0018:ffffc900041270c0 EFLAGS: 00010287
RAX: ffffffff8359efce RBX: 0000000000000008 RCX: 0000000000080000
RDX: ffffc900120da000 RSI: 0000000000021d71 RDI: 0000000000021d72
RBP: ffffc900041271b0 R08: 0000000000000000 R09: 0000000000000008
R10: 00000000fffffffc R11: 0000000000000002 R12: dffffc0000000000
R13: 0000000000000000 R14: ffff888043a01000 R15: 0000000000000001
FS: 00007fe3bbdcc6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbc4095df98 CR3: 000000005fadd000 CR4: 00000000003506e0


---
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syzbot

unread,
Nov 9, 2025, 8:37:28 AM (12 days ago) Nov 9
to syzkaller...@googlegroups.com
syzbot has found a reproducer for the following issue on:

HEAD commit: 0a805b6ea8cd Linux 6.6.116
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=135e517c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=12606d4b8832c7e4
dashboard link: https://syzkaller.appspot.com/bug?extid=a11ccf24c7d55bec632b
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=115b8412580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=175e517c580000
mounted in repro: https://storage.googleapis.com/syzbot-assets/840300b4cdce/mount_0.gz
fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=123a4b42580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a11ccf...@syzkaller.appspotmail.com

(syz.0.17,5949,1):ocfs2_read_blocks_sync:112 ERROR: status = -12
(syz.0.17,5949,1):update_backups:188 ERROR: status = -12
ocfs2: Failed to update super blocks on 7,0 during fs resize. This condition is not fatal, but fsck.ocfs2 should be run to fix it
------------[ cut here ]------------
kernel BUG at fs/ocfs2/suballoc.c:1349!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 5949 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:ocfs2_block_group_set_bits+0x53e/0x670 fs/ocfs2/suballoc.c:1349
Code: ff 44 89 f9 80 e1 07 fe c1 38 c1 0f 8c 8e fd ff ff 4c 89 ff e8 e3 fa 82 fe e9 81 fd ff ff e8 c9 9f 2b fe 0f 0b e8 c2 9f 2b fe <0f> 0b f3 0f 1e fa 65 44 8b 3d f0 c7 a9 7c bf 07 00 00 00 44 89 fe
RSP: 0018:ffffc9000461f0c0 EFLAGS: 00010293
RAX: ffffffff8359efce RBX: 0000000000000008 RCX: ffff888078803c00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000008
RBP: ffffc9000461f1b0 R08: 0000000000000000 R09: 0000000000000008
R10: 00000000fffffffc R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000000 R14: ffff88807687b000 R15: 0000000000000001
FS: 000055557748d500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5f7ba96000 CR3: 00000000771d0000 CR4: 00000000003506e0
Call Trace:
<TASK>
ocfs2_search_one_group fs/ocfs2/suballoc.c:1717 [inline]
ocfs2_claim_suballoc_bits+0x1434/0x2230 fs/ocfs2/suballoc.c:1915
__ocfs2_claim_clusters+0x302/0x900 fs/ocfs2/suballoc.c:2338
ocfs2_add_clusters_in_btree+0x337/0xf60 fs/ocfs2/alloc.c:4827
ocfs2_add_inode_data fs/ocfs2/file.c:550 [inline]
ocfs2_extend_allocation+0x9fd/0x1760 fs/ocfs2/file.c:630
ocfs2_allocate_unwritten_extents+0x2ea/0x7b0 fs/ocfs2/file.c:1495
__ocfs2_change_file_space+0x8d6/0xe40 fs/ocfs2/file.c:2022
ocfs2_fallocate+0x1f5/0x240 fs/ocfs2/file.c:2137
vfs_fallocate+0x58e/0x700 fs/open.c:324
ksys_fallocate fs/open.c:347 [inline]
__do_sys_fallocate fs/open.c:355 [inline]
__se_sys_fallocate fs/open.c:353 [inline]
__x64_sys_fallocate+0xc1/0x110 fs/open.c:353
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f1c17f8f6c9
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:00007ffc1f32cba8 EFLAGS: 00000246 ORIG_RAX: 000000000000011d
RAX: ffffffffffffffda RBX: 00007f1c181e5fa0 RCX: 00007f1c17f8f6c9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00007f1c18011f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000008000c62 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1c181e5fa0 R14: 00007f1c181e5fa0 R15: 0000000000000004
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:ocfs2_block_group_set_bits+0x53e/0x670 fs/ocfs2/suballoc.c:1349
Code: ff 44 89 f9 80 e1 07 fe c1 38 c1 0f 8c 8e fd ff ff 4c 89 ff e8 e3 fa 82 fe e9 81 fd ff ff e8 c9 9f 2b fe 0f 0b e8 c2 9f 2b fe <0f> 0b f3 0f 1e fa 65 44 8b 3d f0 c7 a9 7c bf 07 00 00 00 44 89 fe
RSP: 0018:ffffc9000461f0c0 EFLAGS: 00010293
RAX: ffffffff8359efce RBX: 0000000000000008 RCX: ffff888078803c00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000008
RBP: ffffc9000461f1b0 R08: 0000000000000000 R09: 0000000000000008
R10: 00000000fffffffc R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000000 R14: ffff88807687b000 R15: 0000000000000001
FS: 000055557748d500(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5f7baae000 CR3: 00000000771d0000 CR4: 00000000003506f0


---
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