---
id: CVE-2023-53503
title: 'ext4: allow ext4_get_group_info() to fail'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ext4: allow ext4_get_group_info() to fail

  Previously, ext4_get_group_info() would treat an invalid group number
  as BUG(), since in theory it should never happen.  Howe…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 2f2e09eb15849562aede80ed007658e4504ded26 <
    100c0ad6c04597fefeaaba2bb1827cc015d95067
  - >-
    Linux >= 2f2e09eb15849562aede80ed007658e4504ded26 <
    620a3c28221bb219b81bc0bffd065cc187494302
  - >-
    Linux >= 2f2e09eb15849562aede80ed007658e4504ded26 <
    b4319e457d6e3fb33e443efeaf4634fc36e8a9ed
  - >-
    Linux >= 2f2e09eb15849562aede80ed007658e4504ded26 <
    31668cebf45adfb6283e465e641c4f5a21b07afa
  - >-
    Linux >= 2f2e09eb15849562aede80ed007658e4504ded26 <
    5354b2af34064a4579be8bc0e2f15a7b70f14b5f
  - Linux 3.11
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-05T20:22:31.245711Z'
published: '2025-10-01'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T20:31:12.137Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2023-53503'
references:
  - url: 'https://git.kernel.org/stable/c/100c0ad6c04597fefeaaba2bb1827cc015d95067'
  - url: 'https://git.kernel.org/stable/c/620a3c28221bb219b81bc0bffd065cc187494302'
  - url: 'https://git.kernel.org/stable/c/b4319e457d6e3fb33e443efeaf4634fc36e8a9ed'
  - url: 'https://git.kernel.org/stable/c/31668cebf45adfb6283e465e641c4f5a21b07afa'
  - url: 'https://git.kernel.org/stable/c/5354b2af34064a4579be8bc0e2f15a7b70f14b5f'
tags:
  - cve.org
epss: 0.00159
epssPercentile: 0.05087
ingestedAt: '2026-11-05T22:38:31.803Z'
---

## Overview

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

ext4: allow ext4_get_group_info() to fail

Previously, ext4_get_group_info() would treat an invalid group number
as BUG(), since in theory it should never happen.  However, if a
malicious attaker (or fuzzer) modifies the superblock via the block
device while it is the file system is mounted, it is possible for
s_first_data_block to get set to a very large number.  In that case,
when calculating the block group of some block number (such as the
starting block of a preallocation region), could result in an
underflow and very large block group number.  Then the BUG_ON check in
ext4_get_group_info() would fire, resutling in a denial of service
attack that can be triggered by root or someone with write access to
the block device.

For a quality of implementation perspective, it's best that even if
the system administrator does something that they shouldn't, that it
will not trigger a BUG.  So instead of BUG'ing, ext4_get_group_info()
will call ext4_error and return NULL.  We also add fallback code in
all of the callers of ext4_get_group_info() that it might NULL.

Also, since ext4_get_group_info() was already borderline to be an
inline function, un-inline it.  The results in a next reduction of the
compiled text size of ext4 by roughly 2k.

## Affected

- `Linux >= 2f2e09eb15849562aede80ed007658e4504ded26 < 100c0ad6c04597fefeaaba2bb1827cc015d95067`
- `Linux >= 2f2e09eb15849562aede80ed007658e4504ded26 < 620a3c28221bb219b81bc0bffd065cc187494302`
- `Linux >= 2f2e09eb15849562aede80ed007658e4504ded26 < b4319e457d6e3fb33e443efeaf4634fc36e8a9ed`
- `Linux >= 2f2e09eb15849562aede80ed007658e4504ded26 < 31668cebf45adfb6283e465e641c4f5a21b07afa`
- `Linux >= 2f2e09eb15849562aede80ed007658e4504ded26 < 5354b2af34064a4579be8bc0e2f15a7b70f14b5f`
- `Linux 3.11`

## Remediation

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