Bug 2516366 (CVE-2026-72180)

Summary: CVE-2026-72180 kernel: mm/huge_memory: preserve pmd_swp_uffd_wp on device-private PMD downgrade
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's huge memory management (mm/huge_memory). When a device-private Page Middle Directory (PMD) is downgraded, the pmd_swp_uffd_wp bit, which indicates Userfault File Descriptor Write Protect (UFFD_WP), is not properly preserved. This oversight allows a local attacker to bypass write protection mechanisms by performing an mprotect() operation over a UFFD_WP-marked device-private Transparent Huge Page (THP), potentially leading to unauthorized memory modifications.
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Description OSIDB Bzimport 2026-08-15 06:08:44 UTC 
In the Linux kernel, the following vulnerability has been resolved:

mm/huge_memory: preserve pmd_swp_uffd_wp on device-private PMD downgrade

change_non_present_huge_pmd() rewrites a writable device-private PMD swap
entry into a readable one without carrying pmd_swp_uffd_wp() across.  The
PTE-level change_softleaf_pte() does this correctly; mirror that here,
matching what copy_huge_pmd() does for the fork path.  Without the carry,
a plain mprotect() over a UFFD_WP-marked device-private THP strips the bit
and the trap is bypassed on swap-in.
Comment 1 Keith Grant 2026-08-18 14:27:17 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081539-CVE-2026-72180-854c@gregkh/T