CVE-2021-47450 Information

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().

Reference

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