# CVE-2022-49075: btrfs: fix qgroup reserve overflow the qgroup limit

> An integer overflow in the Linux kernel btrfs filesystem allows bypassing quota limits when fallocating large files, requiring quota features to be enabled.

- **Severity:** High 8.1 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 26 Feb 2025
- **Updated:** 5 Aug 2026
- **Also known as:** DEBIAN-CVE-2022-49075, GHSA-96wx-hqjc-pv4q, UBUNTU-CVE-2022-49075

## What is CVE-2022-49075?

CVE-2022-49075 is a high-severity vulnerability in Linux kernel, published on 26 Feb 2025. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

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

btrfs: fix qgroup reserve overflow the qgroup limit

We use extent_changeset->bytes_changed in qgroup_reserve_data() to record
how many bytes we set for EXTENT_QGROUP_RESERVED state. Currently the
bytes_changed is set as "unsigned int", and it will overflow if we try to
fallocate a range larger than 4GiB. The result is we reserve less bytes
and eventually break the qgroup limit.

Unlike regular buffered/direct write, which we use one changeset for
each ordered extent, which can never be larger than 256M.  For
fallocate, we use one changeset for the whole range, thus it no longer
respects the 256M per extent limit, and caused the problem.

The following example test script reproduces the problem:

  $ cat qgroup-overflow.sh
  #!/bin/bash

  DEV=/dev/sdj
  MNT=/mnt/sdj

  mkfs.btrfs -f $DEV
  mount $DEV $MNT

  # Set qgroup limit to 2GiB.
  btrfs quota enable $MNT
  btrfs qgroup limit 2G $MNT

  # Try to fallocate a 3GiB file. This should fail.
  echo
  echo "Try to fallocate a 3GiB file..."
  fallocate -l 3G $MNT/3G.file

  # Try to fallocate a 5GiB file.
  echo
  echo "Try to fallocate a 5GiB file..."
  fallocate -l 5G $MNT/5G.file

  # See we break the qgroup limit.
  echo
  sync
  btrfs qgroup show -r $MNT

  umount $MNT

When running the test:

  $ ./qgroup-overflow.sh
  (...)

  Try to fallocate a 3GiB file...
  fallocate: fallocate failed: Disk quota exceeded

  Try to fallocate a 5GiB file...

  qgroupid         rfer         excl     max_rfer
  --------         ----         ----     --------
  0/5           5.00GiB      5.00GiB      2.00GiB

Since we have no control of how bytes_changed is used, it's better to
set it to u64.

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2022-49075?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2022-49075?

Apply the vendor's patch.

## Is CVE-2022-49075 being exploited?

There is no known exploitation of CVE-2022-49075 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2022-49075 and fix it if it is affected.

What it is: CVE-2022-49075 is a high-severity vulnerability in Linux kernel, published on 26 Feb 2025. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2022-49075 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2022-49075/ (Markdown: https://insights.sbomify.com/CVE-2022-49075/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2022-49075
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2022-49075
- OSV: https://osv.dev/vulnerability/CVE-2022-49075

---
From sbomify Insights: https://insights.sbomify.com/CVE-2022-49075/
Summaries are generated and may contain mistakes; the official description above is the record.