From f1b9dd5eb86cec1fcf66aad17e7701d98d024a9a Mon Sep 17 00:00:00 2001 From: Jim Mattson Date: Mon, 17 Dec 2018 13:53:33 -0800 Subject: [PATCH] kvm: Disallow wraparound in kvm_gfn_to_hva_cache_init MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Previously, in the case where (gpa + len) wrapped around, the entire region was not validated, as the comment claimed. It doesn't actually seem that wraparound should be allowed here at all. Furthermore, since some callers don't check the return code from this function, it seems prudent to clear ghc->memslot in the event of an error. Fixes: 8f964525a121f ("KVM: Allow cross page reads and writes from cached translations.") Reported-by: Cfir Cohen Signed-off-by: Jim Mattson Reviewed-by: Cfir Cohen Reviewed-by: Marc Orr Cc: Andrew Honig Signed-off-by: Radim Krčmář --- virt/kvm/kvm_main.c | 41 +++++++++++++++++++++-------------------- 1 file changed, 21 insertions(+), 20 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 0041947b7390..3be46841db06 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2005,32 +2005,33 @@ static int __kvm_gfn_to_hva_cache_init(struct kvm_memslots *slots, gfn_t end_gfn = (gpa + len - 1) >> PAGE_SHIFT; gfn_t nr_pages_needed = end_gfn - start_gfn + 1; gfn_t nr_pages_avail; + int r = start_gfn <= end_gfn ? 0 : -EINVAL; ghc->gpa = gpa; ghc->generation = slots->generation; ghc->len = len; - ghc->memslot = __gfn_to_memslot(slots, start_gfn); - ghc->hva = gfn_to_hva_many(ghc->memslot, start_gfn, NULL); - if (!kvm_is_error_hva(ghc->hva) && nr_pages_needed <= 1) { + ghc->hva = KVM_HVA_ERR_BAD; + + /* + * If the requested region crosses two memslots, we still + * verify that the entire region is valid here. + */ + while (!r && start_gfn <= end_gfn) { + ghc->memslot = __gfn_to_memslot(slots, start_gfn); + ghc->hva = gfn_to_hva_many(ghc->memslot, start_gfn, + &nr_pages_avail); + if (kvm_is_error_hva(ghc->hva)) + r = -EFAULT; + start_gfn += nr_pages_avail; + } + + /* Use the slow path for cross page reads and writes. */ + if (!r && nr_pages_needed == 1) ghc->hva += offset; - } else { - /* - * If the requested region crosses two memslots, we still - * verify that the entire region is valid here. - */ - while (start_gfn <= end_gfn) { - nr_pages_avail = 0; - ghc->memslot = __gfn_to_memslot(slots, start_gfn); - ghc->hva = gfn_to_hva_many(ghc->memslot, start_gfn, - &nr_pages_avail); - if (kvm_is_error_hva(ghc->hva)) - return -EFAULT; - start_gfn += nr_pages_avail; - } - /* Use the slow path for cross page reads and writes. */ + else ghc->memslot = NULL; - } - return 0; + + return r; } int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc, -- 2.30.2