[syzbot] [ocfs2?] kernel BUG in ocfs2_remove_btree_range (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 89edd36fd801 Merge tag 'xfs-fixes-6.18-rc7' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1235397c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a1db0fea040c2a9f
dashboard link: https://syzkaller.appspot.com/bug?extid=f82afc4d4e74d0ef7a89
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=134d0612580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15c03a12580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-89edd36f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/80049f7c5ae9/vmlinux-89edd36f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/edfae2c36891/bzImage-89edd36f.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/9eefce186dc7/mount_0.gz
fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=16024e92580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f82afc...@syzkaller.appspotmail.com

(syz.0.17,5491,0):ocfs2_truncate_log_needs_flush:5830 ERROR: bug expression: le16_to_cpu(tl->tl_used) > le16_to_cpu(tl->tl_count)
(syz.0.17,5491,0):ocfs2_truncate_log_needs_flush:5830 ERROR: slot 0, invalid truncate log parameters: used = 129, count = 39
------------[ cut here ]------------
kernel BUG at fs/ocfs2/alloc.c:5830!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5491 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_truncate_log_needs_flush fs/ocfs2/alloc.c:5827 [inline]
RIP: 0010:ocfs2_remove_btree_range+0x152f/0x1540 fs/ocfs2/alloc.c:5752
Code: b7 45 00 4c 89 e7 48 c7 c6 16 10 7e 8d ba c6 16 00 00 48 c7 c1 80 d4 aa 8b 41 89 d8 45 89 f9 50 e8 46 20 1e 00 48 83 c4 08 90 <0f> 0b 66 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90
RSP: 0018:ffffc90002b6ecc0 EFLAGS: 00010296
RAX: 1c4f3c72a1dda200 RBX: 0000000000000000 RCX: 1c4f3c72a1dda200
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: ffffc90002b6ef98 R08: ffff88801fe24293 R09: 1ffff11003fc4852
R10: dffffc0000000000 R11: ffffed1003fc4853 R12: ffffc90002b6ed80
R13: ffff88804c09fac0 R14: 1ffff11009813f58 R15: 0000000000000081
FS: 000055556b844500(0000) GS:ffff88808d72f000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000557f72160e20 CR3: 0000000059e03000 CR4: 0000000000352ef0
Call Trace:
<TASK>
ocfs2_commit_truncate+0xb64/0x21d0 fs/ocfs2/alloc.c:7372
ocfs2_truncate_file+0xca2/0x1420 fs/ocfs2/file.c:509
ocfs2_setattr+0x1520/0x1b40 fs/ocfs2/file.c:1212
notify_change+0xc1a/0xf40 fs/attr.c:546
do_truncate+0x1a4/0x220 fs/open.c:68
handle_truncate fs/namei.c:3596 [inline]
do_open fs/namei.c:3979 [inline]
path_openat+0x306c/0x3830 fs/namei.c:4134
do_filp_open+0x1fa/0x410 fs/namei.c:4161
do_sys_openat2+0x121/0x1c0 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1463
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe596b8f749
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:00007ffe6dee1248 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fe596de5fa0 RCX: 00007fe596b8f749
RDX: 000000000000275a RSI: 0000200000000040 RDI: ffffffffffffff9c
RBP: 00007fe596c13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe596de5fa0 R14: 00007fe596de5fa0 R15: 0000000000000004
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:ocfs2_truncate_log_needs_flush fs/ocfs2/alloc.c:5827 [inline]
RIP: 0010:ocfs2_remove_btree_range+0x152f/0x1540 fs/ocfs2/alloc.c:5752
Code: b7 45 00 4c 89 e7 48 c7 c6 16 10 7e 8d ba c6 16 00 00 48 c7 c1 80 d4 aa 8b 41 89 d8 45 89 f9 50 e8 46 20 1e 00 48 83 c4 08 90 <0f> 0b 66 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90
RSP: 0018:ffffc90002b6ecc0 EFLAGS: 00010296
RAX: 1c4f3c72a1dda200 RBX: 0000000000000000 RCX: 1c4f3c72a1dda200
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: ffffc90002b6ef98 R08: ffff88801fe24293 R09: 1ffff11003fc4852
R10: dffffc0000000000 R11: ffffed1003fc4853 R12: ffffc90002b6ed80
R13: ffff88804c09fac0 R14: 1ffff11009813f58 R15: 0000000000000081
FS: 000055556b844500(0000) GS:ffff88808d72f000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000557f7216a138 CR3: 0000000059e03000 CR4: 0000000000352ef0


---
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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
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#syz undup

[Edward Adam Davis]

#syz test

diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
index 162711cc5b20..570d747a00ca 100644
--- a/fs/ocfs2/alloc.c
+++ b/fs/ocfs2/alloc.c
@@ -6164,7 +6164,7 @@ static int ocfs2_get_truncate_log_info(struct ocfs2_super *osb,
struct buffer_head *bh = NULL;
struct ocfs2_dinode *di;
struct ocfs2_truncate_log *tl;
- unsigned int tl_count;
+ unsigned int tl_count, tl_used;

inode = ocfs2_get_system_file_inode(osb,
TRUNCATE_LOG_SYSTEM_INODE,
@@ -6185,8 +6185,10 @@ static int ocfs2_get_truncate_log_info(struct ocfs2_super *osb,
di = (struct ocfs2_dinode *)bh->b_data;
tl = &di->id2.i_dealloc;
tl_count = le16_to_cpu(tl->tl_count);
+ tl_used = le16_to_cpu(tl->tl_used);
if (unlikely(tl_count > ocfs2_truncate_recs_per_inode(osb->sb) ||
- tl_count == 0)) {
+ tl_count == 0) ||
+ tl_used > tl_count) {
status = -EFSCORRUPTED;
iput(inode);
brelse(bh);

[syzbot]

Hello,

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

Reported-by: syzbot+f82afc...@syzkaller.appspotmail.com
Tested-by: syzbot+f82afc...@syzkaller.appspotmail.com

Tested on:

commit: 4941a177 Merge tag 'trace-ringbuffer-v6.18-rc7' of git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1086de12580000

kernel config: https://syzkaller.appspot.com/x/.config?x=a1db0fea040c2a9f
dashboard link: https://syzkaller.appspot.com/bug?extid=f82afc4d4e74d0ef7a89
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=14f16e12580000

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

[Edward Adam Davis]

The fuzz image has a truncate log inode whose tl_used is bigger than
tl_count so it triggers the BUG in ocfs2_truncate_log_needs_flush() [1].

As what the check in ocfs2_truncate_log_needs_flush() does, just do
same check into ocfs2_get_truncate_log_info() when truncate log inode
is reading in so we can bail out earlier.

[1]

(syz.0.17,5491,0):ocfs2_truncate_log_needs_flush:5830 ERROR: bug expression: le16_to_cpu(tl->tl_used) > le16_to_cpu(tl->tl_count)

kernel BUG at fs/ocfs2/alloc.c:5830!

RIP: 0010:ocfs2_truncate_log_needs_flush fs/ocfs2/alloc.c:5827 [inline]

Call Trace:

ocfs2_commit_truncate+0xb64/0x21d0 fs/ocfs2/alloc.c:7372
ocfs2_truncate_file+0xca2/0x1420 fs/ocfs2/file.c:509
ocfs2_setattr+0x1520/0x1b40 fs/ocfs2/file.c:1212
notify_change+0xc1a/0xf40 fs/attr.c:546
do_truncate+0x1a4/0x220 fs/open.c:68

Reported-by: syzbot+f82afc...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=f82afc4d4e74d0ef7a89
Tested-by: syzbot+f82afc...@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <ead...@qq.com>
---
fs/ocfs2/alloc.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
index 162711cc5b20..570d747a00ca 100644
--- a/fs/ocfs2/alloc.c
+++ b/fs/ocfs2/alloc.c
@@ -6164,7 +6164,7 @@ static int ocfs2_get_truncate_log_info(struct ocfs2_super *osb,
struct buffer_head *bh = NULL;
struct ocfs2_dinode *di;
struct ocfs2_truncate_log *tl;
- unsigned int tl_count;
+ unsigned int tl_count, tl_used;

inode = ocfs2_get_system_file_inode(osb,
TRUNCATE_LOG_SYSTEM_INODE,
@@ -6185,8 +6185,10 @@ static int ocfs2_get_truncate_log_info(struct ocfs2_super *osb,
di = (struct ocfs2_dinode *)bh->b_data;
tl = &di->id2.i_dealloc;
tl_count = le16_to_cpu(tl->tl_count);
+ tl_used = le16_to_cpu(tl->tl_used);
if (unlikely(tl_count > ocfs2_truncate_recs_per_inode(osb->sb) ||
- tl_count == 0)) {
+ tl_count == 0 ||

+ tl_used > tl_count)) {

status = -EFSCORRUPTED;
iput(inode);
brelse(bh);

--
2.43.0

[Joseph Qi]

On 2025/11/27 11:26, Edward Adam Davis wrote:
> The fuzz image has a truncate log inode whose tl_used is bigger than
> tl_count so it triggers the BUG in ocfs2_truncate_log_needs_flush() [1].
>
> As what the check in ocfs2_truncate_log_needs_flush() does, just do
> same check into ocfs2_get_truncate_log_info() when truncate log inode
> is reading in so we can bail out earlier.
>
> [1]
> (syz.0.17,5491,0):ocfs2_truncate_log_needs_flush:5830 ERROR: bug expression: le16_to_cpu(tl->tl_used) > le16_to_cpu(tl->tl_count)
> kernel BUG at fs/ocfs2/alloc.c:5830!
> RIP: 0010:ocfs2_truncate_log_needs_flush fs/ocfs2/alloc.c:5827 [inline]
> Call Trace:
> ocfs2_commit_truncate+0xb64/0x21d0 fs/ocfs2/alloc.c:7372
> ocfs2_truncate_file+0xca2/0x1420 fs/ocfs2/file.c:509
> ocfs2_setattr+0x1520/0x1b40 fs/ocfs2/file.c:1212
> notify_change+0xc1a/0xf40 fs/attr.c:546
> do_truncate+0x1a4/0x220 fs/open.c:68
>
> Reported-by: syzbot+f82afc...@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=f82afc4d4e74d0ef7a89
> Tested-by: syzbot+f82afc...@syzkaller.appspotmail.com
> Signed-off-by: Edward Adam Davis <ead...@qq.com>

Reviewed-by: Joseph Qi <jose...@linux.alibaba.com>