Commit 8a3caa6d authored Nov 18, 2013 by Heiko Carstens Committed by Gleb Natapov Nov 21, 2013

KVM: kvm_clear_guest_page(): fix empty_zero_page usage

Using the address of 'empty_zero_page' as source address in order to
clear a page is wrong. On some architectures empty_zero_page is only the
pointer to the struct page of the empty_zero_page. Therefore the clear
page operation would copy the contents of a couple of struct pages instead
of clearing a page. For kvm only arm/arm64 are affected by this bug.

To fix this use the ZERO_PAGE macro instead which will return the struct
page address of the empty_zero_page on all architectures.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>

parent 521ee0cf

virt/kvm/kvm_main.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -1615,8 +1615,9 @@ EXPORT_SYMBOL_GPL(kvm_read_guest_cached);

		int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len)
		{
		return kvm_write_guest_page(kvm, gfn, (const void *) empty_zero_page,
		offset, len);
		const void zero_page = (const void ) __va(page_to_phys(ZERO_PAGE(0)));

		return kvm_write_guest_page(kvm, gfn, zero_page, offset, len);
		}
		EXPORT_SYMBOL_GPL(kvm_clear_guest_page);