Re: [PATCHv3] KVM: x86: Fix memory leak in vmx.c

[Gleb Natapov <gleb@redhat.com>]

On Thu, Apr 18, 2013 at 09:38:14AM -0700, Andrew Honig wrote:
> 
> If userspace creates and destroys multiple VMs within the same process
> we leak 20k of memory in the userspace process context per VM.  This
> patch frees the memory in kvm_arch_destroy_vm.  If the process exits
> without closing the VM file descriptor or the file descriptor has been
> shared with another process then we don't free the memory.
> 
> It's still possible for a user space process to leak memory if the last
> process to close the fd for the VM is not the process that created it.
> However, this is an unexpected case that's only caused by a user space
> process that's misbehaving.
> 
> Signed-off-by: Andrew Honig <ahonig@google.com>
Reviewed-by: Gleb Natapov <gleb@redhat.com>

> ---
>  arch/x86/kvm/x86.c |   17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 8ffac42..3b389bf 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6856,6 +6856,23 @@ void kvm_arch_sync_events(struct kvm *kvm)
>  
>  void kvm_arch_destroy_vm(struct kvm *kvm)
>  {
> +	if (current->mm == kvm->mm) {
> +		/*
> +		 * Free memory regions allocated on behalf of userspace,
> +		 * unless the the memory map has changed due to process exit
> +		 * or fd copying.
> +		 */
> +		struct kvm_userspace_memory_region mem;
> +		memset(&mem, 0, sizeof(mem));
> +		mem.slot = APIC_ACCESS_PAGE_PRIVATE_MEMSLOT;
> +		kvm_set_memory_region(kvm, &mem);
> +
> +		mem.slot = IDENTITY_PAGETABLE_PRIVATE_MEMSLOT;
> +		kvm_set_memory_region(kvm, &mem);
> +
> +		mem.slot = TSS_PRIVATE_MEMSLOT;
> +		kvm_set_memory_region(kvm, &mem);
> +	}
>  	kvm_iommu_unmap_guest(kvm);
>  	kfree(kvm->arch.vpic);
>  	kfree(kvm->arch.vioapic);
> -- 
> 1.7.10.4
> 
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--
			Gleb.