ghsa-5jw6-g45h-9h97
Vulnerability from github
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)
{
"affected": [],
"aliases": [
"CVE-2025-21939"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-04-01T16:15:24Z",
"severity": null
},
"details": "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)",
"id": "GHSA-5jw6-g45h-9h97",
"modified": "2025-04-01T18:30:52Z",
"published": "2025-04-01T18:30:52Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-21939"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0a98219bcc961edd3388960576e4353e123b4a51"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2a24c98f0e4cc994334598d4f3a851972064809d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f9326f529da7298a95643c3267f1c0fdb0db55eb"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
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