---
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: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    9740dd0c17a4be8cc47a06c5ca5293471a7e286e
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    59f75e0c8724d4adebc08c7dd3ff2358b80c21f7
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    18d32b0013efba19f7ad3e5b08d7aee813d604a6
  - Linux < 6.12.111
  - Linux < 6.18.53
  - Linux (all versions)
published: '2026-09-24'
updated: '2026-09-25'
sourceUpdated: '2026-09-25T13:17:25.150'
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/59f75e0c8724d4adebc08c7dd3ff2358b80c21f7'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/9740dd0c17a4be8cc47a06c5ca5293471a7e286e'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-24T16:47:15.885Z'
---

## 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.