From: Heiko Carstens Date: Mon, 18 Nov 2013 09:35:55 +0000 (+0100) Subject: KVM: kvm_clear_guest_page(): fix empty_zero_page usage X-Git-Tag: firefly_0821_release~176^2~4896^2 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=8a3caa6d74597c2a083f7c87f866891a0b12540b;p=firefly-linux-kernel-4.4.55.git 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 Signed-off-by: Gleb Natapov --- diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 662f34c3287e..a0aa84b5941a 100644 --- a/virt/kvm/kvm_main.c +++ b/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);