---
id: CVE-2026-97416
title: >-
  In the Linux kernel, the following vulnerability has been resolved:


  btrfs: balance: fix potential bg lookup failure in
  btrfs_may_alloc_data_chunk()


  [BUG]

  Running btrfs balance can trigger a null-ptr-deref before relocating a

  data chunk…
summary: >-
  In the Linux kernel, the following vulnerability has been resolved:


  btrfs: balance: fix potential bg lookup failure in
  btrfs_may_alloc_data_chunk()


  [BUG]

  Running btrfs balance can trigger a null-ptr-deref before relocating a

  data chunk…
severity: medium
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= a6f93c71d412ba8ed743152c3a54ad0b78dcd9c7 <
    9f37a6d6ae9e998232e2ba091ab4999cdf967e1b
  - >-
    Linux >= a6f93c71d412ba8ed743152c3a54ad0b78dcd9c7 <
    e479236a8f4d85c4fb6b3f7c2556c21f583e2bf2
  - >-
    Linux >= a6f93c71d412ba8ed743152c3a54ad0b78dcd9c7 <
    322f891b4d4fe64acb3351a0ffa62a7fa5ba7256
  - >-
    Linux >= a6f93c71d412ba8ed743152c3a54ad0b78dcd9c7 <
    81a664ed8b1a44c76b204c4bd0d751317a02c5cd
  - >-
    Linux >= a6f93c71d412ba8ed743152c3a54ad0b78dcd9c7 <
    9740dd0c17a4be8cc47a06c5ca5293471a7e286e
  - >-
    Linux >= a6f93c71d412ba8ed743152c3a54ad0b78dcd9c7 <
    59f75e0c8724d4adebc08c7dd3ff2358b80c21f7
  - >-
    Linux >= a6f93c71d412ba8ed743152c3a54ad0b78dcd9c7 <
    18d32b0013efba19f7ad3e5b08d7aee813d604a6
  - Linux 4.16
published: '2026-09-24'
updated: '2026-10-03'
sourceUpdated: '2026-10-03T11:17:53.617'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-97416'
references:
  - url: 'https://git.kernel.org/stable/c/18d32b0013efba19f7ad3e5b08d7aee813d604a6'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/322f891b4d4fe64acb3351a0ffa62a7fa5ba7256'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/59f75e0c8724d4adebc08c7dd3ff2358b80c21f7'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/81a664ed8b1a44c76b204c4bd0d751317a02c5cd'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/9740dd0c17a4be8cc47a06c5ca5293471a7e286e'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/9f37a6d6ae9e998232e2ba091ab4999cdf967e1b'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/e479236a8f4d85c4fb6b3f7c2556c21f583e2bf2'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-97416.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-97416'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2540566'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-97416'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-97416'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-97416.mbox
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
epss: 0.00173
epssPercentile: 0.06644
ingestedAt: '2026-09-24T16:47:15.885Z'
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
cvssSource: vendor
cwe:
  - CWE-476
---

## Overview

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

btrfs: balance: fix potential bg lookup failure in btrfs_may_alloc_data_chunk()

[BUG]
Running btrfs balance can trigger a null-ptr-deref before relocating a
data chunk when metadata corruption leaves a chunk in the chunk tree
without a corresponding block group in the in-memory cache:

  KASAN: null-ptr-deref in range [0x0000000000000088-0x000000000000008f]
  RIP: 0010:btrfs_may_alloc_data_chunk+0x40/0x1c0 fs/btrfs/volumes.c:3601
  Call Trace:
    __btrfs_balance fs/btrfs/volumes.c:4217 [inline]
    btrfs_balance+0x2516/0x42b0 fs/btrfs/volumes.c:4604
    btrfs_ioctl_balance fs/btrfs/ioctl.c:3577 [inline]
    btrfs_ioctl+0x25cf/0x5b90 fs/btrfs/ioctl.c:5313
    ...

[CAUSE]
__btrfs_balance() iterates the on-disk chunk tree and passes the chunk
logical bytenr to btrfs_may_alloc_data_chunk() before relocating a data
chunk. That helper then queries the in-memory block group cache:

  cache = btrfs_lookup_block_group(fs_info, chunk_offset);
  chunk_type = cache->flags;   /* cache may be NULL */

A corrupt image can contain a chunk item whose matching block group
item is missing, so no block group is ever inserted into the cache. In
that case btrfs_lookup_block_group() returns NULL.

The code only guards this with ASSERT(cache), which becomes a no-op when
CONFIG_BTRFS_ASSERT is disabled. The subsequent dereference of
cache->flags therefore crashes the kernel.

[FIX]
Add a NULL check after btrfs_lookup_block_group() in
btrfs_may_alloc_data_chunk() and print and error message for clarity.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **Red Hat VEX** · Low · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 10 · updated 2026-10-17 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-97416.json)