FKIE_CVE-2026-98067

Vulnerability from fkie_nvd - Published: 2026-09-25 11:17 - Updated: 2026-10-21 13:21
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: erofs: disable LZ4 rolling decompression for now LZ4 rolling decompression [1] was introduced to reduce the memory footprint of temporary pages: For many cases, it is needed for users to read small data within a compressed extent (pcluster), either due to random small read, or since uptodate folios (typically order-0) cannot be reused for decompression again since decompression algorithm refills already-uptodate folios. Rolling decompression works because LZ4 is LZ77-based and only refers to the most recent 64 KiB of decompressed data, so in theory only a bounded rolling window of temporary pages is needed when decompressing. It can save a lot of temporary memory, e.g. 601,960-byte data can be compressed into a 256k LZ4 compressed extent, which means it needs 146 extra pages per request in the worst case if rolling decompression is disabled. However, the upstream LZ4 implementation is not under EROFS' control: For example, the literal copy memmove() may still **copy long literals backward** on x86 based on the address comparison even when the source and destination ranges do not overlap (IOWs, inline decompression doesn't need to be considered here). That breaks the rolling assumption and makes the optimization broken. Disable it for now to make sure the data correctness first since EROFS is used everywhere now: The rolling window approach can be revived once we either ensure that the official LZ4 code always copies forward for non-overlapping ranges or maintain our own LZ4 implementation in EROFS. The main impact is a higher runtime memory footprint; However, recent commit 0f6273ab4637 ("erofs: add a reserved buffer pool for lz4 decompression") helps mitigate this when enabled but it's still not perfect. [1] https://www.usenix.org/conference/atc19/presentation/gao § 3.3 Decompression
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/82e664cf1219c459c33aae931b222cf951af9cb7
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c9a2db4b9950b59c571258e4bae74c271f62dd66
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d923e53472b468a50a6cf41341531d5170c68371
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/dcc5e6c9e4d06fe73fc61e730ee3e51dd115a4d8
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ec52dfed7b14514ed97ee71161e4cf4cfe2fbff2
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/erofs/decompressor.c",
            "fs/erofs/internal.h",
            "fs/erofs/zdata.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "dcc5e6c9e4d06fe73fc61e730ee3e51dd115a4d8",
              "status": "affected",
              "version": "8e6c8fa9f2e95c88a642521a5da19a8e31748846",
              "versionType": "git"
            },
            {
              "lessThan": "d923e53472b468a50a6cf41341531d5170c68371",
              "status": "affected",
              "version": "8e6c8fa9f2e95c88a642521a5da19a8e31748846",
              "versionType": "git"
            },
            {
              "lessThan": "ec52dfed7b14514ed97ee71161e4cf4cfe2fbff2",
              "status": "affected",
              "version": "8e6c8fa9f2e95c88a642521a5da19a8e31748846",
              "versionType": "git"
            },
            {
              "lessThan": "c9a2db4b9950b59c571258e4bae74c271f62dd66",
              "status": "affected",
              "version": "8e6c8fa9f2e95c88a642521a5da19a8e31748846",
              "versionType": "git"
            },
            {
              "lessThan": "82e664cf1219c459c33aae931b222cf951af9cb7",
              "status": "affected",
              "version": "8e6c8fa9f2e95c88a642521a5da19a8e31748846",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/erofs/decompressor.c",
            "fs/erofs/internal.h",
            "fs/erofs/zdata.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.13"
            },
            {
              "lessThan": "5.13",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.160",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.114",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.53",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.7",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nerofs: disable LZ4 rolling decompression for now\n\nLZ4 rolling decompression [1] was introduced to reduce the memory\nfootprint of temporary pages:\n\n For many cases, it is needed for users to read small data within\n a compressed extent (pcluster), either due to random small read, or\n since uptodate folios (typically order-0) cannot be reused for\n decompression again since decompression algorithm refills\n already-uptodate folios.\n\nRolling decompression works because LZ4 is LZ77-based and only refers\nto the most recent 64 KiB of decompressed data, so in theory only a\nbounded rolling window of temporary pages is needed when decompressing.\n\nIt can save a lot of temporary memory, e.g.\n 601,960-byte data can be compressed into a 256k LZ4 compressed extent,\n which means it needs 146 extra pages per request in the worst case if\n rolling decompression is disabled.\n\nHowever, the upstream LZ4 implementation is not under EROFS\u0027 control:\nFor example, the literal copy memmove() may still **copy long literals\nbackward** on x86 based on the address comparison even when the source\nand destination ranges do not overlap (IOWs, inline decompression\ndoesn\u0027t need to be considered here). That breaks the rolling assumption\nand makes the optimization broken.\n\nDisable it for now to make sure the data correctness first since EROFS\nis used everywhere now: The rolling window approach can be revived once\nwe either ensure that the official LZ4 code always copies forward for\nnon-overlapping ranges or maintain our own LZ4 implementation in EROFS.\n\nThe main impact is a higher runtime memory footprint; However, recent\ncommit 0f6273ab4637 (\"erofs: add a reserved buffer pool for lz4\ndecompression\") helps mitigate this when enabled but it\u0027s still not\nperfect.\n\n[1] https://www.usenix.org/conference/atc19/presentation/gao\n    \u00a7 3.3 Decompression"
    }
  ],
  "id": "CVE-2026-98067",
  "lastModified": "2026-10-21T13:21:21.163",
  "metrics": {},
  "published": "2026-09-25T11:17:35.787",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/82e664cf1219c459c33aae931b222cf951af9cb7"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c9a2db4b9950b59c571258e4bae74c271f62dd66"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d923e53472b468a50a6cf41341531d5170c68371"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/dcc5e6c9e4d06fe73fc61e730ee3e51dd115a4d8"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/ec52dfed7b14514ed97ee71161e4cf4cfe2fbff2"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}



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