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/[email protected]/>)
would probably be making the impact of this a lot worse.

https://git.kernel.org/stable/c/0708fd6bd8161871bfbadced2ca4319b84ab44fe

https://git.kernel.org/stable/c/0a8f806ea6b5dd64b3d1f05ff774817d5f7ddbd1

https://git.kernel.org/stable/c/320ac1af4c0bdb92c864dc9250d1329234820edf

https://git.kernel.org/stable/c/3ef938c3503563bfc2ac15083557f880d29c2e64

https://git.kernel.org/stable/c/556d446068f90981e5d71ca686bdaccdd545d491

https://git.kernel.org/stable/c/618d5612ecb7bfc1c85342daafeb2b47e29e77a3

https://git.kernel.org/stable/c/7085895c59e4057ffae17f58990ccb630087d0d2

https://git.kernel.org/stable/c/78d6f9a9eb2a5da6fcbd76d6191d24b0dcc321be

https://git.kernel.org/stable/c/93224deb50a8d20df3884f3672ce9f982129aa50