{"id":"CVE-2025-21939","title":"In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/xe/hmm: Don't dereference struct page pointers without notifier lock\n\nThe pnfs that we obtain from hmm_range_fault() point to pages that\nwe don't have a reference o…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/xe/hmm: Don't dereference struct page pointers without notifier lock\n\nThe pnfs that we obtain from hmm_range_fault() point to pages that\nwe don't have a reference o…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cwe":["CWE-476","CWE-667"],"vendor":"linux","product":"linux_kernel","affected":["linux_kernel >= 6.10, < 6.12.19","linux_kernel >= 6.13, < 6.13.7","linux_kernel = 6.14"],"patched":["linux_kernel 6.13.7"],"published":"2025-04-01","updated":"2026-10-15","sourceUpdated":"2026-10-15T22:18:12.333","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2025-21939","references":[{"url":"https://git.kernel.org/stable/c/0a98219bcc961edd3388960576e4353e123b4a51","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/2a24c98f0e4cc994334598d4f3a851972064809d","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/f9326f529da7298a95643c3267f1c0fdb0db55eb","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-21939.json"},{"url":"https://access.redhat.com/security/cve/CVE-2025-21939"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2356586"},{"url":"https://www.cve.org/CVERecord?id=CVE-2025-21939"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2025-21939"},{"url":"https://lore.kernel.org/linux-cve-announce/2025040135-CVE-2025-21939-b7d7@gregkh/T"}],"tags":["nvd","cve.org","csaf","vex","red-hat"],"epss":0.00216,"epssPercentile":0.1196,"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-15T21:43:50.870417Z"},"scores":{"nvd":7.8,"vendor":6.1},"ingestedAt":"2026-07-30T18:55:15.060Z","slug":"CVE-2025-21939","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\ndrm/xe/hmm: Don't dereference struct page pointers without notifier lock\n\nThe pnfs that we obtain from hmm_range_fault() point to pages that\nwe don't 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's 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't own dirty and accessed, and\nit also avoid dereferencing struct pages that we don't 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't 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)\n\n## Affected\n\n- `linux_kernel >= 6.10, < 6.12.19`\n- `linux_kernel >= 6.13, < 6.13.7`\n- `linux_kernel = 6.14`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 6.13.7`\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9 · updated 2026-10-21 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-21939.json)","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}