GHSA-VQPJ-F54G-HRC3

Vulnerability from github – Published: 2026-10-23 15:31 – Updated: 2026-10-23 15:31
VLAI
Details

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

dm ioctl: don't let data_start run past the buffer

struct dm_ioctl has seven bytes of trailing padding, so the smallest buffer userspace is allowed to ask for, offsetof(struct dm_ioctl, data), is seven bytes shorter than sizeof(struct dm_ioctl).

get_result_buffer() sets data_start to sizeof(struct dm_ioctl) without looking at how big the buffer actually is. Ask for the minimum and data_start ends up seven bytes past the end. Callers add it to data_size, and ctl_ioctl() copies that much back to userspace:

BUG: KASAN: slab-out-of-bounds in _copy_to_user+0xad/0xd0 Read of size 312 at addr ffff8880169e4c00 by task repro-dm/140 ctl_ioctl+0x5e3/0xcb0 dm_ctl_ioctl+0x25/0x40 allocated 305-byte region [ffff8880169e4c00, ffff8880169e4d31)

A DM_LIST_DEVICES with data_size set to 305 is enough to hit it, and the seven bytes that leak are whatever sat next to the allocation.

Clamp data_start to the buffer size.

Note that this is not a security bug because the out-of-bounds read can only be triggered by root.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-99063"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-23T13:17:30Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ndm ioctl: don\u0027t let data_start run past the buffer\n\nstruct dm_ioctl has seven bytes of trailing padding, so the smallest\nbuffer userspace is allowed to ask for, offsetof(struct dm_ioctl, data),\nis seven bytes shorter than sizeof(struct dm_ioctl).\n\nget_result_buffer() sets data_start to sizeof(struct dm_ioctl) without\nlooking at how big the buffer actually is. Ask for the minimum and\ndata_start ends up seven bytes past the end. Callers add it to\ndata_size, and ctl_ioctl() copies that much back to userspace:\n\n  BUG: KASAN: slab-out-of-bounds in _copy_to_user+0xad/0xd0\n  Read of size 312 at addr ffff8880169e4c00 by task repro-dm/140\n   ctl_ioctl+0x5e3/0xcb0\n   dm_ctl_ioctl+0x25/0x40\n  allocated 305-byte region [ffff8880169e4c00, ffff8880169e4d31)\n\nA DM_LIST_DEVICES with data_size set to 305 is enough to hit it, and the\nseven bytes that leak are whatever sat next to the allocation.\n\nClamp data_start to the buffer size.\n\nNote that this is not a security bug because the out-of-bounds read can\nonly be triggered by root.",
  "id": "GHSA-vqpj-f54g-hrc3",
  "modified": "2026-10-23T15:31:37Z",
  "published": "2026-10-23T15:31:37Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99063"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5680b6fb3054677d4ee65d3baba24b649f1b430e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/725b49c689bbb29ef740b0d6b5ea9390baa9a695"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/98195e822343a656b92e235847ab3e72b1a3f920"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9b3fcf519d370df94a56f3b272d9eddffffa5be8"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e5c3f3d8935ecc64c962fb66e6a86dbf79218f61"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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