CVE-2025-22045 — x86/mm: Fix flush_tlb_range() when used for zapping normal PMDs

Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

x86/mm: Fix flush_tlb_range() when used for zapping normal PMDs

On the following path, flush_tlb_range() can be used for zapping normal PMD entries (PMD entries that point to page tables) together with the PTE entries in the pointed-to page table:

collapse_pte_mapped_thp pmdp_collapse_flush flush_tlb_range

The arm64 version of flush_tlb_range() has a comment describing that it can be used for page table removal, and does not use any last-level invalidation optimizations. Fix the X86 version by making it behave the same way.

Currently, X86 only uses this information for the following two purposes, which I think means the issue doesn't have much impact:

- In native_flush_tlb_multi() for checking if lazy TLB CPUs need to be IPI'd to avoid issues with speculative page table walks. - In Hyper-V TLB paravirtualization, again for lazy TLB stuff.

The patch "x86/mm: only invalidate final translations with INVLPGB" which is currently under review (see <https://lore.kernel.org/all/20241230175550.4046587-13-riel@surriel.com/>) would probably be making the impact of this a lot worse.

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CVE-2025-22045 — x86/mm: Fix flush_tlb_range() when used for zapping normal PMDs