---
id: CVE-2026-93048
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  mtd: part: reject MTDPART_OFS_RETAIN in mtd_add_partition()

  mtd_add_partition() does not reject the special offset value
  MTDPART_OFS_RETAIN (-3), which leads to a WARN…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  mtd: part: reject MTDPART_OFS_RETAIN in mtd_add_partition()

  mtd_add_partition() does not reject the special offset value
  MTDPART_OFS_RETAIN (-3), which leads to a WARN…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 1a31368bf92ef2a7da3ba379672c405bd2751df9 <
    701c3ae7273e1adc20db5d97c42e0139b479f16b
  - >-
    Linux >= 1a31368bf92ef2a7da3ba379672c405bd2751df9 <
    6aaab2ace3f7b55733d904e5549acf8405f03642
  - >-
    Linux >= 1a31368bf92ef2a7da3ba379672c405bd2751df9 <
    181c1bff940e7d3e34ca485d37e3cdbfe409203c
  - >-
    Linux >= 1a31368bf92ef2a7da3ba379672c405bd2751df9 <
    a536eb57be58442b19398b2783071007ecfb1735
  - >-
    Linux >= 1a31368bf92ef2a7da3ba379672c405bd2751df9 <
    e204e5c49a012f99638633fdbd773e3c86260053
  - >-
    Linux >= 1a31368bf92ef2a7da3ba379672c405bd2751df9 <
    398aca2f90122d5abbabff1079deaeb885fe9e40
  - >-
    Linux >= 1a31368bf92ef2a7da3ba379672c405bd2751df9 <
    c645f6dd1af2ecc70fd3578e141f2f71fa9e4eff
  - >-
    Linux >= 1a31368bf92ef2a7da3ba379672c405bd2751df9 <
    b759d5bb6265419344ee9729fd0dc07ad85719d8
  - Linux 3.2
published: '2026-09-17'
updated: '2026-09-17'
sourceUpdated: '2026-09-17T17:17:58.080'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-93048'
references:
  - url: 'https://git.kernel.org/stable/c/181c1bff940e7d3e34ca485d37e3cdbfe409203c'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/398aca2f90122d5abbabff1079deaeb885fe9e40'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/6aaab2ace3f7b55733d904e5549acf8405f03642'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/701c3ae7273e1adc20db5d97c42e0139b479f16b'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/a536eb57be58442b19398b2783071007ecfb1735'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/b759d5bb6265419344ee9729fd0dc07ad85719d8'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/c645f6dd1af2ecc70fd3578e141f2f71fa9e4eff'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/e204e5c49a012f99638633fdbd773e3c86260053'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-17T16:21:47.772Z'
epss: 0.00211
epssPercentile: 0.11595
---

## Overview

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

mtd: part: reject MTDPART_OFS_RETAIN in mtd_add_partition()

mtd_add_partition() does not reject the special offset value
MTDPART_OFS_RETAIN (-3), which leads to a WARN_ON in
add_mtd_device() when called through the BLKPG ioctl on NAND
devices. The RETAIN value depends on cur_offset being the end of
the previous partition, but in the dynamic partition path
cur_offset equals the offset argument itself, causing undefined
behavior.

Commit 5daa7b21496a ("mtd: prepare partition add and del functions
for ioctl requests") introduced mtd_add_partition() and correctly
rejected MTDPART_OFS_APPEND (-1) and MTDPART_OFS_NXTBLK (-2),
since those special offsets rely on cur_offset tracking the
previous partition's end. However, commit 1a31368bf92e ("mtd: add a flags
for partitions which should just leave smth. after them")
later added MTDPART_OFS_RETAIN (-3) for the static
partition table path without updating mtd_add_partition() to
also reject this value.

With offset=-3 passed via BLKPG, the RETAIN size calculation in
allocate_partition() underflows (parent_size - 0xFFFFFFFFFFFFFFFD
= parent_size + 3). If the underflow result does not appear to
leave enough space, allocate_partition() jumps to out_register via
goto, skipping erasesize initialization. This results in
erasesize=0, which triggers:

WARN_ON((!mtd->erasesize || !master->_erase) &&
		!(mtd->flags & MTD_NO_ERASE))

in add_mtd_device(). If the underflow result appears to leave
enough space, a bogus partition size is calculated, but the
"out of reach" sanity check catches the invalid offset and
creates a disabled empty partition (offset=0, size=0) instead
of returning an error.

Fix this by adding MTDPART_OFS_RETAIN to the rejection list in
mtd_add_partition(), consistent with the existing handling of
APPEND and NXTBLK.

## Remediation

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