Commit 51776043 authored Oct 26, 2017 by Paolo Bonzini Committed by Kees Cook Jan 15, 2018

kvm: x86: fix KVM_XEN_HVM_CONFIG ioctl



This ioctl is obsolete (it was used by Xenner as far as I know) but
still let's not break it gratuitously...  Its handler is copying
directly into struct kvm.  Go through a bounce buffer instead, with
the added benefit that we can actually do something useful with the
flags argument---the previous code was exiting with -EINVAL but still
doing the copy.

This technically is a userspace ABI breakage, but since no one should be
using the ioctl, it's a good occasion to see if someone actually
complains.

Cc: kernel-hardening@lists.openwall.com
Cc: Kees Cook <keescook@chromium.org>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>

parent 46515736

arch/x86/kvm/x86.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -4238,13 +4238,14 @@ set_identity_unlock:
		mutex_unlock(&kvm->lock);
		break;
		case KVM_XEN_HVM_CONFIG: {
		struct kvm_xen_hvm_config xhc;
		r = -EFAULT;
		if (copy_from_user(&kvm->arch.xen_hvm_config, argp,
		sizeof(struct kvm_xen_hvm_config)))
		if (copy_from_user(&xhc, argp, sizeof(xhc)))
		goto out;
		r = -EINVAL;
		if (kvm->arch.xen_hvm_config.flags)
		if (xhc.flags)
		goto out;
		memcpy(&kvm->arch.xen_hvm_config, &xhc, sizeof(xhc));
		r = 0;
		break;
		}

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