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f8be156be1
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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