mtd: part: reject MTDPART_OFS_RETAIN in mtd_add_partition()

Description

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.

Timeline

Scores

No CVSS score yet: neither the CNA, CISA nor NVD has scored this CVE. NVD status: Received.

EPSS (exploitation in 30 days)

0.22% · top 88% of all CVEs (11 Nov 2026)

The list uses the assigner's score when there is one, then CISA's, then NVD's: Not scored.

Affected products

• Linux · Linux

  • affected 1a31368bf92ef2a7da3ba379672c405bd2751df9 – < 701c3ae7273e1adc20db5d97c42e0139b479f16b
  • affected 1a31368bf92ef2a7da3ba379672c405bd2751df9 – < 6aaab2ace3f7b55733d904e5549acf8405f03642
  • affected 1a31368bf92ef2a7da3ba379672c405bd2751df9 – < 181c1bff940e7d3e34ca485d37e3cdbfe409203c
  • affected 1a31368bf92ef2a7da3ba379672c405bd2751df9 – < a536eb57be58442b19398b2783071007ecfb1735
  • affected 1a31368bf92ef2a7da3ba379672c405bd2751df9 – < e204e5c49a012f99638633fdbd773e3c86260053
  • affected 1a31368bf92ef2a7da3ba379672c405bd2751df9 – < 398aca2f90122d5abbabff1079deaeb885fe9e40
  • affected 1a31368bf92ef2a7da3ba379672c405bd2751df9 – < c645f6dd1af2ecc70fd3578e141f2f71fa9e4eff
  • affected 1a31368bf92ef2a7da3ba379672c405bd2751df9 – < b759d5bb6265419344ee9729fd0dc07ad85719d8

• Linux · Linux

  • affected 3.2
  • unaffected < 3.2
  • unaffected 5.10.270 – ≤ 5.10.*
  • unaffected 5.15.221 – ≤ 5.15.*
  • unaffected 6.1.188 – ≤ 6.1.*
  • unaffected 6.6.157 – ≤ 6.6.*
  • unaffected 6.12.110 – ≤ 6.12.*
  • unaffected 6.18.52 – ≤ 6.18.*
  • unaffected 7.2.6 – ≤ 7.2.*
  • unaffected 7.3 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2026-82158 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-93048](https://cveledger.app/badge/CVE-2026-93048.svg)](https://cveledger.app/cve/CVE-2026-93048)

Record last updated 19 Oct 2026, 09:04 UTC.