Commit 46515736 authored Oct 26, 2017 by Paolo Bonzini Committed by Kees Cook Jan 15, 2018

kvm: whitelist struct kvm_vcpu_arch



On x86, ARM and s390, struct kvm_vcpu_arch has a usercopy region
that is read and written by the KVM_GET/SET_CPUID2 ioctls (x86)
or KVM_GET/SET_ONE_REG (ARM/s390).  Without whitelisting the area,
KVM is completely broken on those architectures with usercopy hardening
enabled.

For now, allow writing to the entire struct on all architectures.
The KVM tree will not refine this to an architecture-specific
subset of struct kvm_vcpu_arch.

Cc: kernel-hardening@lists.openwall.com
Cc: Kees Cook <keescook@chromium.org>
Cc: Christian Borntraeger <borntraeger@redhat.com>
Cc: Christoffer Dall <cdall@linaro.org>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Kees Cook <keescook@chromium.org>

parent 08626a60

virt/kvm/kvm_main.c

+6 −2

Original line number	Original line	Diff line number	Diff line
	@@ -4029,8 +4029,12 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
	/* A kmem cache lets us meet the alignment requirements of fx_save. */		/* A kmem cache lets us meet the alignment requirements of fx_save. */
	if (!vcpu_align)		if (!vcpu_align)
	vcpu_align = __alignof__(struct kvm_vcpu);		vcpu_align = __alignof__(struct kvm_vcpu);
	kvm_vcpu_cache = kmem_cache_create("kvm_vcpu", vcpu_size, vcpu_align,		kvm_vcpu_cache =
	SLAB_ACCOUNT, NULL);		kmem_cache_create_usercopy("kvm_vcpu", vcpu_size, vcpu_align,
			SLAB_ACCOUNT,
			offsetof(struct kvm_vcpu, arch),
			sizeof_field(struct kvm_vcpu, arch),
			NULL);
	if (!kvm_vcpu_cache) {		if (!kvm_vcpu_cache) {
	r = -ENOMEM;		r = -ENOMEM;
	goto out_free_3;		goto out_free_3;