# CVE-2023-54158: btrfs: don't free qgroup space unless specified

> A logic error in the Linux kernel btrfs filesystem can cause a resource leak, leading to denial of service when qgroups are enabled.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Dec 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2023-54158, DEBIAN-CVE-2023-54158, GHSA-crmq-c99h-f986, UBUNTU-CVE-2023-54158

## What is CVE-2023-54158?

CVE-2023-54158 is a denial of service vulnerability in Linux, published on 24 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

btrfs: don't free qgroup space unless specified

Boris noticed in his simple quotas testing that he was getting a leak
with Sweet Tea's change to subvol create that stopped doing a
transaction commit.  This was just a side effect of that change.

In the delayed inode code we have an optimization that will free extra
reservations if we think we can pack a dir item into an already modified
leaf.  Previously this wouldn't be triggered in the subvolume create
case because we'd commit the transaction, it was still possible but
much harder to trigger.  It could actually be triggered if we did a
mkdir && subvol create with qgroups enabled.

This occurs because in btrfs_insert_delayed_dir_index(), which gets
called when we're adding the dir item, we do the following:

  btrfs_block_rsv_release(fs_info, trans->block_rsv, bytes, NULL);

if we're able to skip reserving space.

The problem here is that trans->block_rsv points at the temporary block
rsv for the subvolume create, which has qgroup reservations in the block
rsv.

This is a problem because btrfs_block_rsv_release() will do the
following:

  if (block_rsv->qgroup_rsv_reserved >= block_rsv->qgroup_rsv_size) {
	  qgroup_to_release = block_rsv->qgroup_rsv_reserved -
		  block_rsv->qgroup_rsv_size;
	  block_rsv->qgroup_rsv_reserved = block_rsv->qgroup_rsv_size;
  }

The temporary block rsv just has ->qgroup_rsv_reserved set,
->qgroup_rsv_size == 0.  The optimization in
btrfs_insert_delayed_dir_index() sets ->qgroup_rsv_reserved = 0.  Then
later on when we call btrfs_subvolume_release_metadata() which has

  btrfs_block_rsv_release(fs_info, rsv, (u64)-1, &qgroup_to_release);
  btrfs_qgroup_convert_reserved_meta(root, qgroup_to_release);

qgroup_to_release is set to 0, and we do not convert the reserved
metadata space.

The problem here is that the block rsv code has been unconditionally
messing with ->qgroup_rsv_reserved, because the main place this is used
is delalloc, and any time we call btrfs_block_rsv_release() we do it
with qgroup_to_release set, and thus do the proper accounting.

The subvolume code is the only other code that uses the qgroup
reservation stuff, but it's intermingled with the above optimization,
and thus was getting its reservation freed out from underneath it and
thus leaking the reserved space.

The solution is to simply not mess with the qgroup reservations if we
don't have qgroup_to_release set.  This works with the existing code as
anything that messes with the delalloc reservations always have
qgroup_to_release set.  This fixes the leak that Boris was observing.

## Which versions are affected by CVE-2023-54158?


## How do I fix CVE-2023-54158?

Apply the vendor's patch.

## Is CVE-2023-54158 being exploited?

There is no known exploitation of CVE-2023-54158 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-54158 and fix it if it is affected.

What it is: CVE-2023-54158 is a denial of service vulnerability in Linux, published on 24 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2023-54158 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2023-54158/ (Markdown: https://insights.sbomify.com/CVE-2023-54158/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-54158
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-54158
- OSV: https://osv.dev/vulnerability/CVE-2023-54158

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-54158/
Summaries are generated and may contain mistakes; the official description above is the record.