kvm: Disallow wraparound in kvm_gfn_to_hva_cache_init (f1b9dd5e) · Commits · 戴 / test

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: ("KVM: Allow cross page reads and writes from cached translations.") Reported-by:

Cfir Cohen <cfir@google.com> Signed-off-by:

Jim Mattson <jmattson@google.com> Reviewed-by:

Cfir Cohen <cfir@google.com> Reviewed-by:

Marc Orr <marcorr@google.com> Cc: Andrew Honig <ahonig@google.com> Signed-off-by:

Radim Krčmář <rkrcmar@redhat.com>

virt/kvm/kvm_main.c

+21 −20

Original line number	Diff line number	Diff line
		@@ -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 += offset;
		} else {
		ghc->hva = KVM_HVA_ERR_BAD;

		/*
		* 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;
		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))
		return -EFAULT;
		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
		ghc->memslot = NULL;
		}
		return 0;

		return r;
		}

		int kvm_gfn_to_hva_cache_init(struct kvm kvm, struct gfn_to_hva_cache ghc,

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