ghsa-wm4c-jgh8-m62g
Vulnerability from github
Published
2024-05-17 15:31
Modified
2024-06-26 00:31
Details

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

KVM: SVM: Flush pages under kvm->lock to fix UAF in svm_register_enc_region()

Do the cache flush of converted pages in svm_register_enc_region() before dropping kvm->lock to fix use-after-free issues where region and/or its array of pages could be freed by a different task, e.g. if userspace has __unregister_enc_region_locked() already queued up for the region.

Note, the "obvious" alternative of using local variables doesn't fully resolve the bug, as region->pages is also dynamically allocated. I.e. the region structure itself would be fine, but region->pages could be freed.

Flushing multiple pages under kvm->lock is unfortunate, but the entire flow is a rare slow path, and the manual flush is only needed on CPUs that lack coherency for encrypted memory.

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{
  "affected": [],
  "aliases": [
    "CVE-2024-35791"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-05-17T13:15:58Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SVM: Flush pages under kvm-\u003elock to fix UAF in svm_register_enc_region()\n\nDo the cache flush of converted pages in svm_register_enc_region() before\ndropping kvm-\u003elock to fix use-after-free issues where region and/or its\narray of pages could be freed by a different task, e.g. if userspace has\n__unregister_enc_region_locked() already queued up for the region.\n\nNote, the \"obvious\" alternative of using local variables doesn\u0027t fully\nresolve the bug, as region-\u003epages is also dynamically allocated.  I.e. the\nregion structure itself would be fine, but region-\u003epages could be freed.\n\nFlushing multiple pages under kvm-\u003elock is unfortunate, but the entire\nflow is a rare slow path, and the manual flush is only needed on CPUs that\nlack coherency for encrypted memory.",
  "id": "GHSA-wm4c-jgh8-m62g",
  "modified": "2024-06-26T00:31:42Z",
  "published": "2024-05-17T15:31:08Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-35791"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/12f8e32a5a389a5d58afc67728c76e61beee1ad4"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2d13b79640b147bd77c34a5998533b2021a4122d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4868c0ecdb6cfde7c70cf478c46e06bb9c7e5865"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5ef1d8c1ddbf696e47b226e11888eaf8d9e8e807"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e126b508ed2e616d679d85fca2fbe77bb48bbdd7"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f6d53d8a2617dd58c89171a6b9610c470ebda38a"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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