GHSA-X237-C35R-5VQ5

Vulnerability from github – Published: 2026-06-25 09:31 – Updated: 2026-06-30 03:37
VLAI
Details

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

drm/gem: Try to fix change_handle ioctl, attempt 4

[airlied: just added some comments on how to reenable] On-list because the cat is out of the bag and we're clearly not good enough to figure this out in private. The story thus far:

5e28b7b94408 ("drm: Set old handle to NULL before prime swap in change_handle") tried to fix a race condition between the gem_close and gem_change_handle ioctls, but got a few things wrong:

  • There's a confusion with the local variable handle, which is actually the new handle, and so the two-stage trick was actually applied to the wrong idr slot. 7164d78559b0 ("drm/gem: fix race between change_handle and handle_delete") tried to fix that by adding yet another code block, but forgot to add the error handling. Which meant we now have two paths, both kinda wrong.

  • dc366607c41c ("drm: Replace old pointer to new idr") tried to apply another fix, but inconsistently, again because of the handle confusion

  • this would be the right fix (kinda, somewhat, it's a mess) if we'd do the two-stage approach for the new handle. Except that wasn't the intent of the original fix.

We also didn't have an igt merged for the original ioctl, which is a big no-go. This was attempted to address off-list in the original bugfix, and amd QA people claimed the bug was fixed now. Very clearly that's not the case. Here's my attempt to sort this out:

  • Rename the local variable to new_handle, the old aliasing with args->handle is just too dangerously confusing.

  • Merge the gem obj lookup with the two-stage idr_replace so that we avoid getting ourselves confused there.

  • This means we don't have a surplus temporary reference anymore, only an inherited from the idr. A concurrent gem_close on the new_handle could steal that. Fix that with the same two-stage approach create_tail uses. This is a bit overkill as documented in the comment, but I also don't trust my ability to understand this all correctly, so go with the established pattern we have from other ioctls instead for maximum paranoia.

  • Adjust error paths. I've tried to make the error and success paths common, because they are identical except for which handle is removed and on which we call idr_replace to (re)install the object again. But that made things messier to read, so I've left it at the more verbose version, which unfortunately hides the symmetry in the entire code flow a bit.

  • While at it, also replace the 7 space indent with 1 tab.

And finally, because I flat out don't trust my abilities here at all anymore:

  • Disable the ioctl until we have the igt situation and everything else sorted out on-list and with full consensus.

v2:

Sashiko noticed that I didn't handle the error path for idr_replace correctly, it must be checked with IS_ERR_OR_NULL like in gem_handle_delete. So yeah, definitely should just the existing paths 1:1 because this is endless amounts of tricky.

Also add the Fixes: line for the original ioctl, I forgot that too.

Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-53145"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-367"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-06-25T09:16:31Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/gem: Try to fix change_handle ioctl, attempt 4\n\n[airlied: just added some comments on how to reenable]\nOn-list because the cat is out of the bag and we\u0027re clearly not good\nenough to figure this out in private. The story thus far:\n\n5e28b7b94408 (\"drm: Set old handle to NULL before prime swap in\nchange_handle\") tried to fix a race condition between the gem_close and\ngem_change_handle ioctls, but got a few things wrong:\n\n- There\u0027s a confusion with the local variable handle, which is actually\n  the new handle, and so the two-stage trick was actually applied to the\n  wrong idr slot. 7164d78559b0 (\"drm/gem: fix race between\n  change_handle and handle_delete\") tried to fix that by adding yet\n  another code block, but forgot to add the error handling. Which meant\n  we now have two paths, both kinda wrong.\n\n- dc366607c41c (\"drm: Replace old pointer to new idr\") tried to apply\n  another fix, but inconsistently, again because of the handle confusion\n  - this would be the right fix (kinda, somewhat, it\u0027s a mess) if we\u0027d\n  do the two-stage approach for the new handle. Except that wasn\u0027t the\n  intent of the original fix.\n\nWe also didn\u0027t have an igt merged for the original ioctl, which is a big\nno-go. This was attempted to address off-list in the original bugfix,\nand amd QA people claimed the bug was fixed now. Very clearly that\u0027s not\nthe case. Here\u0027s my attempt to sort this out:\n\n- Rename the local variable to new_handle, the old aliasing with\n  args-\u003ehandle is just too dangerously confusing.\n\n- Merge the gem obj lookup with the two-stage idr_replace so that we\n  avoid getting ourselves confused there.\n\n- This means we don\u0027t have a surplus temporary reference anymore, only\n  an inherited from the idr. A concurrent gem_close on the new_handle\n  could steal that. Fix that with the same two-stage approach\n  create_tail uses. This is a bit overkill as documented in the comment,\n  but I also don\u0027t trust my ability to understand this all correctly, so\n  go with the established pattern we have from other ioctls instead for\n  maximum paranoia.\n\n- Adjust error paths. I\u0027ve tried to make the error and success paths\n  common, because they are identical except for which handle is removed\n  and on which we call idr_replace to (re)install the object again. But\n  that made things messier to read, so I\u0027ve left it at the more verbose\n  version, which unfortunately hides the symmetry in the entire code\n  flow a bit.\n\n- While at it, also replace the 7 space indent with 1 tab.\n\nAnd finally, because I flat out don\u0027t trust my abilities here at all\nanymore:\n\n- Disable the ioctl until we have the igt situation and everything else\n  sorted out on-list and with full consensus.\n\nv2:\n\nSashiko noticed that I didn\u0027t handle the error path for idr_replace\ncorrectly, it must be checked with IS_ERR_OR_NULL like in\ngem_handle_delete. So yeah, definitely should just the existing paths\n1:1 because this is endless amounts of tricky.\n\nAlso add the Fixes: line for the original ioctl, I forgot that too.",
  "id": "GHSA-x237-c35r-5vq5",
  "modified": "2026-06-30T03:37:13Z",
  "published": "2026-06-25T09:31:19Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53145"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/security/cve/CVE-2026-53145"
    },
    {
      "type": "WEB",
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2492773"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1a4f03d22fb655e5f192244fb2c87d8066fcfca2"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1d9b93df7fc768228906e24220591ec1cddad391"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c0639ede2f24ac224b2079cd35ecd5fd8ad4e3cd"
    },
    {
      "type": "WEB",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-53145.json"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}


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