GHSA-788X-356F-432M

Vulnerability from github – Published: 2026-09-25 12:31 – Updated: 2026-09-25 12:31
VLAI
Details

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

smb/client: validate new EOF for zero range

When FALLOC_FL_ZERO_RANGE is used without FALLOC_FL_KEEP_SIZE, smb3_zero_range() may extend EOF without checking RLIMIT_FSIZE, allowing the file to grow beyond the caller's file-size limit.

Fix this by calling inode_newsize_ok() before sending the zero-range request when the operation would extend EOF.

Reproducer, using a file on a CIFS mount:

bash -c '
        FILE=/mnt/cifs/repro

        trap "" SIGXFSZ
        ulimit -f 3072

        truncate -s 2M "$FILE"
        fallocate --zero-range -o 0 -l 4M "$FILE"
        echo "fallocate rc=$?"
        stat -c "file size=%s" "$FILE"
'

Before this change, the operation succeeds despite the 3 MiB limit:

fallocate rc=0
file size=4194304

After this change, fallocate fails and leaves the file at 2 MiB.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-98126"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-25T11:17:43Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb/client: validate new EOF for zero range\n\nWhen FALLOC_FL_ZERO_RANGE is used without FALLOC_FL_KEEP_SIZE,\nsmb3_zero_range() may extend EOF without checking RLIMIT_FSIZE, allowing\nthe file to grow beyond the caller\u0027s file-size limit.\n\nFix this by calling inode_newsize_ok() before sending the zero-range\nrequest when the operation would extend EOF.\n\nReproducer, using a file on a CIFS mount:\n\n\tbash -c \u0027\n\t        FILE=/mnt/cifs/repro\n\n\t        trap \"\" SIGXFSZ\n\t        ulimit -f 3072\n\n\t        truncate -s 2M \"$FILE\"\n\t        fallocate --zero-range -o 0 -l 4M \"$FILE\"\n\t        echo \"fallocate rc=$?\"\n\t        stat -c \"file size=%s\" \"$FILE\"\n\t\u0027\n\nBefore this change, the operation succeeds despite the 3 MiB limit:\n\n\tfallocate rc=0\n\tfile size=4194304\n\nAfter this change, fallocate fails and leaves the file at 2 MiB.",
  "id": "GHSA-788x-356f-432m",
  "modified": "2026-09-25T12:31:37Z",
  "published": "2026-09-25T12:31:37Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98126"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/06a4f9049cb6dc319bceec2dc813ba89add8b828"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3673f057b64abfa957e8ae84448db69369a5091a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/88972e35750792e717af287dc71f42a03b5cbce4"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f320ca20c273a26cd779bdb2b2e4b076a95c76f6"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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