CVE-2026-89805
HighCVSS 7.8Summary
A bug was fixed in the Linux kernel's drm/pagemap module in the drm_pagemap_migrate_populate_ram_pfn() function. Higher-order folio allocations lacked the __GFP_NOWARN flag and a fallback path, and in the free_pages error path the folio order was computed after put_page() had already dropped the reference, leading to a use-after-free. The source page array construction was also corrected to ensure full copying after demotion to order-0 folios.
Risk Assessment
A use-after-free vulnerability in the kernel can lead to memory corruption, system crash (kernel panic), or potential arbitrary code execution with kernel privileges. In multi-tenant environments it could be exploited for privilege escalation.
Recommendation
Update the Linux kernel to a version containing the fix for CVE-2026-89805. If immediate update is not possible, consider restricting access to DRM/pagemap functionality or monitoring for unusual kernel crashes.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: drm/pagemap: Fix folio allocation fallback and use-after-put drm_pagemap_migrate_populate_ram_pfn() had two issues when populating RAM PFNs with higher-order folios: 1. The higher-order vma_alloc_folio()/folio_alloc() calls did not pass __GFP_NOWARN, so a THP allocation failure under memory pressure would spam the kernel log, and there was no fallback path despite a TODO comment stating one was needed. Add __GFP_NOWARN to the higher-order allocation and, on failure, fall back to order-0 allocations for the entire range originally covered by the failed higher-order allocation, leaving MIGRATE_PFN_COMPOUND unset for those PFNs. 2. In the free_pages error path, order was computed via folio_order(page_folio(page)) *after* put_page(page) had already dropped the reference, resulting in a use-after-free/put when that was the last reference on the page. Compute order before releasing the page. Introducing the fallback in 1. also requires the source page array handed to ->copy_to_ram() to be built differently. Both callers only populated the entry at the head of each source folio, relying on the copy callback to derive the rest of the folio from the order recorded in the matching drm_pagemap_addr. Once the destination has been demoted to order-0 folios the drm_pagemap_addr entries are per-page, so a source page is needed for every one of them; leaving them NULL makes the copy callback stop after the first page and the remainder of the range is never copied. The source folio is only split later, by migrate_vma_pages() / migrate_device_pages(), so its order cannot be used to detect the demotion - test the destination for MIGRATE_PFN_COMPOUND instead. Factor the array population out into drm_pagemap_migrate_populate_src_pages() and use it from both drm_pagemap_evict_to_ram() and __drm_pagemap_migrate_to_ram().
Vulnerability data from NVD (NIST) · CISA KEV · EPSS