ghsa-c47v-8m9c-7hhr
Vulnerability from github
Published
2025-09-05 18:31
Modified
2025-09-05 18:31
Details

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

gfs2: Validate i_depth for exhash directories

A fuzzer test introduced corruption that ends up with a depth of 0 in dir_e_read(), causing an undefined shift by 32 at:

index = hash >> (32 - dip->i_depth);

As calculated in an open-coded way in dir_make_exhash(), the minimum depth for an exhash directory is ilog2(sdp->sd_hash_ptrs) and 0 is invalid as sdp->sd_hash_ptrs is fixed as sdp->bsize / 16 at mount time.

So we can avoid the undefined behaviour by checking for depth values lower than the minimum in gfs2_dinode_in(). Values greater than the maximum are already being checked for there.

Also switch the calculation in dir_make_exhash() to use ilog2() to clarify how the depth is calculated.

Tested with the syzkaller repro.c and xfstests '-g quick'.

Show details on source website

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{
  "affected": [],
  "aliases": [
    "CVE-2025-38710"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-09-04T16:15:40Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ngfs2: Validate i_depth for exhash directories\n\nA fuzzer test introduced corruption that ends up with a depth of 0 in\ndir_e_read(), causing an undefined shift by 32 at:\n\n  index = hash \u003e\u003e (32 - dip-\u003ei_depth);\n\nAs calculated in an open-coded way in dir_make_exhash(), the minimum\ndepth for an exhash directory is ilog2(sdp-\u003esd_hash_ptrs) and 0 is\ninvalid as sdp-\u003esd_hash_ptrs is fixed as sdp-\u003ebsize / 16 at mount time.\n\nSo we can avoid the undefined behaviour by checking for depth values\nlower than the minimum in gfs2_dinode_in(). Values greater than the\nmaximum are already being checked for there.\n\nAlso switch the calculation in dir_make_exhash() to use ilog2() to\nclarify how the depth is calculated.\n\nTested with the syzkaller repro.c and xfstests \u0027-g quick\u0027.",
  "id": "GHSA-c47v-8m9c-7hhr",
  "modified": "2025-09-05T18:31:17Z",
  "published": "2025-09-05T18:31:16Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-38710"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/53a0249d68a210c16e961b83adfa82f94ee0a53d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/557c024ca7250bb65ae60f16c02074106c2f197b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9680c58675b82348ab84d387e4fa727f7587e1a0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b5f46951e62377b6e406fadc18bc3c5bdf1632a7"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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