{"id":"CVE-2025-21939","summary":"drm/xe/hmm: Don't dereference struct page pointers without notifier lock","details":"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 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)","modified":"2026-04-02T12:45:17.539895Z","published":"2025-04-01T15:41:05.393Z","related":["SUSE-SU-2025:02254-1","SUSE-SU-2025:02307-1","SUSE-SU-2025:02333-1"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21939.json","cna_assigner":"Linux"},"references":[{"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"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21939.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-21939"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"81e058a3e7fd8593d076b4f26f7b8bb49f1d61e3"},{"fixed":"2a24c98f0e4cc994334598d4f3a851972064809d"},{"fixed":"f9326f529da7298a95643c3267f1c0fdb0db55eb"},{"fixed":"0a98219bcc961edd3388960576e4353e123b4a51"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-21939.json"}}],"schema_version":"1.7.5"}