arm64: contpte: fix set_access_flags() no-op check for SMMU/ATS faults

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Summary

CVECVE-2026-43486
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-13 16:16:51 UTC
Updated2026-05-13 16:16:51 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: arm64: contpte: fix set_access_flags() no-op check for SMMU/ATS faults contpte_ptep_set_access_flags() compared the gathered ptep_get() value against the requested entry to detect no-ops. ptep_get() ORs AF/dirty from all sub-PTEs in the CONT block, so a dirty sibling can make the target appear already-dirty. When the gathered value matches entry, the function returns 0 even though the target sub-PTE still has PTE_RDONLY set in hardware. For a CPU with FEAT_HAFDBS this gathered view is fine, since hardware may set AF/dirty on any sub-PTE and CPU TLB behavior is effectively gathered across the CONT range. But page-table walkers that evaluate each descriptor individually (e.g. a CPU without DBM support, or an SMMU without HTTU, or with HA/HD disabled in CD.TCR) can keep faulting on the unchanged target sub-PTE, causing an infinite fault loop. Gathering can therefore cause false no-ops when only a sibling has been updated: - write faults: target still has PTE_RDONLY (needs PTE_RDONLY cleared) - read faults: target still lacks PTE_AF Fix by checking each sub-PTE against the requested AF/dirty/write state (the same bits consumed by __ptep_set_access_flags()), using raw per-PTE values rather than the gathered ptep_get() view, before returning no-op. Keep using the raw target PTE for the write-bit unfold decision. Per Arm ARM (DDI 0487) D8.7.1 ("The Contiguous bit"), any sub-PTE in a CONT range may become the effective cached translation and software must maintain consistent attributes across the range.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 4602e5757bcceb231c3a13c36c373ad4a750eddb 05d239f2c95e66e27e7fb4e99ee07eb56e3e34b0 git Not specified
CNA Linux Linux affected 4602e5757bcceb231c3a13c36c373ad4a750eddb 6f92a7a8b48a523f910ef25dd83808710724f59b git Not specified
CNA Linux Linux affected 4602e5757bcceb231c3a13c36c373ad4a750eddb 09d620555e59768776090073a2c59d2bc8506eb3 git Not specified
CNA Linux Linux affected 4602e5757bcceb231c3a13c36c373ad4a750eddb 97c5550b763171dbef61e6239cab372b9f9cd4a2 git Not specified
CNA Linux Linux affected 6.9 Not specified
CNA Linux Linux unaffected 6.9 semver Not specified
CNA Linux Linux unaffected 6.12.78 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.19 6.18.* semver Not specified
CNA Linux Linux unaffected 6.19.9 6.19.* semver Not specified
CNA Linux Linux unaffected 7.0 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/6f92a7a8b48a523f910ef25dd83808710724f59b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/05d239f2c95e66e27e7fb4e99ee07eb56e3e34b0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/97c5550b763171dbef61e6239cab372b9f9cd4a2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/09d620555e59768776090073a2c59d2bc8506eb3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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