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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>
master
Heiko Carstens 8 years ago
committed by Gleb Natapov
parent
commit
8a3caa6d74
  1. 5
      virt/kvm/kvm_main.c

5
virt/kvm/kvm_main.c

@ -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);

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