CVE-2025-21939 (GCVE-0-2025-21939)
Vulnerability from cvelistv5
Published
2025-04-01 15:41
Modified
2025-05-04 07:25
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: drm/xe/hmm: Don't dereference struct page pointers without notifier lock The pnfs that we obtain from hmm_range_fault() point to pages that we don't have a reference on, and the guarantee that they are still in the cpu page-tables is that the notifier lock must be held and the notifier seqno is still valid. So while building the sg table and marking the pages accesses / dirty we need to hold this lock with a validated seqno. However, the lock is reclaim tainted which makes sg_alloc_table_from_pages_segment() unusable, since it internally allocates memory. Instead build the sg-table manually. For the non-iommu case this might lead to fewer coalesces, but if that's a problem it can be fixed up later in the resource cursor code. For the iommu case, the whole sg-table may still be coalesced to a single contigous device va region. This avoids marking pages that we don't own dirty and accessed, and it also avoid dereferencing struct pages that we don't own. v2: - Use assert to check whether hmm pfns are valid (Matthew Auld) - Take into account that large pages may cross range boundaries (Matthew Auld) v3: - Don't unnecessarily check for a non-freed sg-table. (Matthew Auld) - Add a missing up_read() in an error path. (Matthew Auld) (cherry picked from commit ea3e66d280ce2576664a862693d1da8fd324c317)
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/0a98219bcc961edd3388960576e4353e123b4a51
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/2a24c98f0e4cc994334598d4f3a851972064809d
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f9326f529da7298a95643c3267f1c0fdb0db55eb
Impacted products
Vendor Product Version
Linux Linux Version: 81e058a3e7fd8593d076b4f26f7b8bb49f1d61e3
Version: 81e058a3e7fd8593d076b4f26f7b8bb49f1d61e3
Version: 81e058a3e7fd8593d076b4f26f7b8bb49f1d61e3
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   Linux Linux Version: 6.10
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{
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        {
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          "product": "Linux",
          "programFiles": [
            "drivers/gpu/drm/xe/xe_hmm.c"
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      "descriptions": [
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/xe/hmm: Don\u0027t dereference struct page pointers without notifier lock\n\nThe pnfs that we obtain from hmm_range_fault() point to pages that\nwe don\u0027t have a reference on, and the guarantee that they are still\nin the cpu page-tables is that the notifier lock must be held and the\nnotifier seqno is still valid.\n\nSo while building the sg table and marking the pages accesses / dirty\nwe need to hold this lock with a validated seqno.\n\nHowever, the lock is reclaim tainted which makes\nsg_alloc_table_from_pages_segment() unusable, since it internally\nallocates memory.\n\nInstead build the sg-table manually. For the non-iommu case\nthis might lead to fewer coalesces, but if that\u0027s a problem it can\nbe fixed up later in the resource cursor code. For the iommu case,\nthe whole sg-table may still be coalesced to a single contigous\ndevice va region.\n\nThis avoids marking pages that we don\u0027t own dirty and accessed, and\nit also avoid dereferencing struct pages that we don\u0027t own.\n\nv2:\n- Use assert to check whether hmm pfns are valid (Matthew Auld)\n- Take into account that large pages may cross range boundaries\n  (Matthew Auld)\n\nv3:\n- Don\u0027t unnecessarily check for a non-freed sg-table. (Matthew Auld)\n- Add a missing up_read() in an error path. (Matthew Auld)\n\n(cherry picked from commit ea3e66d280ce2576664a862693d1da8fd324c317)"
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      "providerMetadata": {
        "dateUpdated": "2025-05-04T07:25:05.653Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        },
        {
          "url": "https://git.kernel.org/stable/c/0a98219bcc961edd3388960576e4353e123b4a51"
        }
      ],
      "title": "drm/xe/hmm: Don\u0027t dereference struct page pointers without notifier lock",
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-21939",
    "datePublished": "2025-04-01T15:41:05.393Z",
    "dateReserved": "2024-12-29T08:45:45.789Z",
    "dateUpdated": "2025-05-04T07:25:05.653Z",
    "state": "PUBLISHED"
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  "dataVersion": "5.1",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-21939\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-04-01T16:15:24.773\",\"lastModified\":\"2025-04-01T20:26:01.990\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\ndrm/xe/hmm: Don\u0027t dereference struct page pointers without notifier lock\\n\\nThe pnfs that we obtain from hmm_range_fault() point to pages that\\nwe don\u0027t have a reference on, and the guarantee that they are still\\nin the cpu page-tables is that the notifier lock must be held and the\\nnotifier seqno is still valid.\\n\\nSo while building the sg table and marking the pages accesses / dirty\\nwe need to hold this lock with a validated seqno.\\n\\nHowever, the lock is reclaim tainted which makes\\nsg_alloc_table_from_pages_segment() unusable, since it internally\\nallocates memory.\\n\\nInstead build the sg-table manually. For the non-iommu case\\nthis might lead to fewer coalesces, but if that\u0027s a problem it can\\nbe fixed up later in the resource cursor code. For the iommu case,\\nthe whole sg-table may still be coalesced to a single contigous\\ndevice va region.\\n\\nThis avoids marking pages that we don\u0027t own dirty and accessed, and\\nit also avoid dereferencing struct pages that we don\u0027t own.\\n\\nv2:\\n- Use assert to check whether hmm pfns are valid (Matthew Auld)\\n- Take into account that large pages may cross range boundaries\\n  (Matthew Auld)\\n\\nv3:\\n- Don\u0027t unnecessarily check for a non-freed sg-table. (Matthew Auld)\\n- Add a missing up_read() in an error path. (Matthew Auld)\\n\\n(cherry picked from commit ea3e66d280ce2576664a862693d1da8fd324c317)\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/0a98219bcc961edd3388960576e4353e123b4a51\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/2a24c98f0e4cc994334598d4f3a851972064809d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/f9326f529da7298a95643c3267f1c0fdb0db55eb\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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