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authorNicholas Piggin <npiggin@gmail.com>2021-06-24 08:29:04 -0400
committerPaolo Bonzini <pbonzini@redhat.com>2021-06-24 11:55:11 -0400
commitf8be156be163a052a067306417cd0ff679068c97 (patch)
tree2f291bec641f75e1f350177da6179e8316699d71 /virt/Makefile
parent309505dd56854c1f9744c9a2b8aa40d897002bca (diff)
KVM: do not allow mapping valid but non-reference-counted pages
It's possible to create a region which maps valid but non-refcounted pages (e.g., tail pages of non-compound higher order allocations). These host pages can then be returned by gfn_to_page, gfn_to_pfn, etc., family of APIs, which take a reference to the page, which takes it from 0 to 1. When the reference is dropped, this will free the page incorrectly. Fix this by only taking a reference on valid pages if it was non-zero, which indicates it is participating in normal refcounting (and can be released with put_page). This addresses CVE-2021-22543. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Tested-by: Paolo Bonzini <pbonzini@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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