{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-21939","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2024-12-29T08:45:45.789Z","datePublished":"2025-04-01T15:41:05.393Z","dateUpdated":"2026-08-05T11:55:29.323Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T11:55:29.323Z"},"descriptions":[{"lang":"en","value":"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)"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The vulnerable path is reached only through Intel Xe DRM ioctls (`DRM_IOCTL_XE_VM_BIND`, `DRM_IOCTL_XE_EXEC`) or GPU page faults raised by the attacker's own submitted workload, all requiring an open handle on the local `/dev/dri/renderD*` node. There is no remote or adjacent-network reachability.\nAC:L - The attacker controls both sides of the race — one thread issues the userptr bind/exec while another munmaps, MADV_DONTNEEDs, or migrates the same user range — and can widen the window arbitrarily by sizing the userptr range so the intervening `kvmalloc_array()` and `sg_alloc_table_from_pages_segment()` GFP_KERNEL allocations enter direct reclaim. No condition outside the attacker's influence is required.\nPR:L - An unprivileged local account with render-node access is sufficient; these are all DRM_RENDER_ALLOW ioctls, and render nodes are granted to ordinary logged-in desktop users, Android apps, and GPU-passthrough containers by default. No CAP_SYS_ADMIN or root is needed.\nUI:N - The attacker triggers the entire sequence from its own threads via ioctls and memory-management syscalls on its own address space. No action by any other user is required.\nS:U - The corruption occurs in kernel page/folio metadata and kernel-managed DMA mappings, within the same security authority as the vulnerable driver. Standard kernel memory corruption leading to local privilege escalation does not cross a scope boundary.\nC:H - This is a use-after-free on unreferenced pages: freed pages can be reallocated to other processes or the kernel and are still DMA-mapped DMA_BIDIRECTIONAL for the GPU and read via struct page dereferences, giving an attacker who grooms the reallocation a path to read memory belonging to other security contexts.\nI:H - `set_page_dirty_lock()` on a reallocated folio calls `mapping->a_ops->dirty_folio()` through a function pointer read from memory the driver no longer owns — a control-flow hijack primitive — and also wrongly dirties foreign page-cache folios (causing writeback of unintended data) while `mark_page_accessed()` corrupts LRU lists. Per kernel UAF guidance this yields arbitrary-write/code-execution potential.\nA:H - Even without full exploitation, LRU list manipulation on a freed folio, breaking another owner's page lock via `folio_unlock()`, and refcount assertions on zero-refcount pages produce list-debug BUGs, oopses, and kernel panics. Any local user with render-node access can trigger this repeatedly."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/gpu/drm/xe/xe_hmm.c"],"versions":[{"version":"81e058a3e7fd8593d076b4f26f7b8bb49f1d61e3","lessThan":"2a24c98f0e4cc994334598d4f3a851972064809d","status":"affected","versionType":"git"},{"version":"81e058a3e7fd8593d076b4f26f7b8bb49f1d61e3","lessThan":"f9326f529da7298a95643c3267f1c0fdb0db55eb","status":"affected","versionType":"git"},{"version":"81e058a3e7fd8593d076b4f26f7b8bb49f1d61e3","lessThan":"0a98219bcc961edd3388960576e4353e123b4a51","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/gpu/drm/xe/xe_hmm.c"],"versions":[{"version":"6.10","status":"affected"},{"version":"0","lessThan":"6.10","status":"unaffected","versionType":"semver"},{"version":"6.12.19","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.13.7","lessThanOrEqual":"6.13.*","status":"unaffected","versionType":"semver"},{"version":"6.14","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"6.12.19"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"6.13.7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"6.14"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/2a24c98f0e4cc994334598d4f3a851972064809d"},{"url":"https://git.kernel.org/stable/c/f9326f529da7298a95643c3267f1c0fdb0db55eb"},{"url":"https://git.kernel.org/stable/c/0a98219bcc961edd3388960576e4353e123b4a51"}],"title":"drm/xe/hmm: Don't dereference struct page pointers without notifier lock","x_generator":{"engine":"bippy-1.2.0"}}}}