2016-10-21 16:40:27

by Ido Yariv

Subject: [PATCH] KVM: x86: fix wbinvd_dirty_mask use-after-free

vcpu->arch.wbinvd_dirty_mask may still be used after freeing it,
corrupting memory. For example, the following call trace may set a bit
in an already freed cpu mask:
kvm_arch_vcpu_load
vcpu_load
vmx_free_vcpu_nested
vmx_free_vcpu
kvm_arch_vcpu_free

Fix this by deferring freeing of wbinvd_dirty_mask.

Cc: [email protected]
Signed-off-by: Ido Yariv <[email protected]>
---
arch/x86/kvm/x86.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 6c633de..9ec8c1d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7410,10 +7410,12 @@ void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)

void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu)
{
+ void *wbinvd_dirty_mask = vcpu->arch.wbinvd_dirty_mask;
+
kvmclock_reset(vcpu);

- free_cpumask_var(vcpu->arch.wbinvd_dirty_mask);
kvm_x86_ops->vcpu_free(vcpu);
+ free_cpumask_var(wbinvd_dirty_mask);
}

struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm,
--
2.5.5

2016-10-24 14:16:01

by Paolo Bonzini

Subject: Re: [PATCH] KVM: x86: fix wbinvd_dirty_mask use-after-free

On 21/10/2016 18:39, Ido Yariv wrote:
> vcpu->arch.wbinvd_dirty_mask may still be used after freeing it,
> corrupting memory. For example, the following call trace may set a bit
> in an already freed cpu mask:
> kvm_arch_vcpu_load
> vcpu_load
> vmx_free_vcpu_nested
> vmx_free_vcpu
> kvm_arch_vcpu_free
>
> Fix this by deferring freeing of wbinvd_dirty_mask.
>
> Cc: [email protected]
> Signed-off-by: Ido Yariv <[email protected]>
> ---
> arch/x86/kvm/x86.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 6c633de..9ec8c1d 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7410,10 +7410,12 @@ void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
>
> void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu)
> {
> + void *wbinvd_dirty_mask = vcpu->arch.wbinvd_dirty_mask;
> +
> kvmclock_reset(vcpu);
>
> - free_cpumask_var(vcpu->arch.wbinvd_dirty_mask);
> kvm_x86_ops->vcpu_free(vcpu);
> + free_cpumask_var(wbinvd_dirty_mask);
> }
>
> struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm,
>

Reviewed-by: Paolo Bonzini <[email protected]>

2016-10-24 15:23:33

by Radim Krčmář

Subject: Re: [PATCH] KVM: x86: fix wbinvd_dirty_mask use-after-free

2016-10-21 12:39-0400, Ido Yariv:
> vcpu->arch.wbinvd_dirty_mask may still be used after freeing it,
> corrupting memory. For example, the following call trace may set a bit
> in an already freed cpu mask:
> kvm_arch_vcpu_load
> vcpu_load
> vmx_free_vcpu_nested
> vmx_free_vcpu
> kvm_arch_vcpu_free
>
> Fix this by deferring freeing of wbinvd_dirty_mask.
>
> Cc: [email protected]
> Signed-off-by: Ido Yariv <[email protected]>
> ---

Applied, thanks.