Vulnerability CVE-2021-47450


Published: 2024-05-22

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

KVM: arm64: Fix host stage-2 PGD refcount

The KVM page-table library refcounts the pages of concatenated stage-2
PGDs individually. However, when running KVM in protected mode, the
host's stage-2 PGD is currently managed by EL2 as a single high-order
compound page, which can cause the refcount of the tail pages to reach 0
when they shouldn't, hence corrupting the page-table.

Fix this by introducing a new hyp_split_page() helper in the EL2 page
allocator (matching the kernel's split_page() function), and make use of
it from host_s2_zalloc_pages_exact().

 References:
https://git.kernel.org/stable/c/b372264c66ef78f2cab44e877fbd765ad6d24c39
https://git.kernel.org/stable/c/1d58a17ef54599506d44c45ac95be27273a4d2b1

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