linux-kernel - Re: [patch] KVM: SVM: prevent DBG_DECRYPT and DBG

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Date:   Fri, 5 Apr 2019 20:50:13 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     David Rientjes <rientjes@...gle.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Joerg Roedel <joro@...tes.org>,
        Radim Krčmář <rkrcmar@...hat.com>
Cc:     Borislav Petkov <bp@...e.de>, x86@...nel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [patch] KVM: SVM: prevent DBG_DECRYPT and DBG_ENCRYPT overflow

On 25/03/19 19:47, David Rientjes wrote:
> This ensures that the address and length provided to DBG_DECRYPT and
> DBG_ENCRYPT do not cause an overflow.
> 
> At the same time, pass the actual number of pages pinned in memory to
> sev_unpin_memory() as a cleanup.
> 
> Reported-by: Cfir Cohen <cfir@...gle.com>
> Signed-off-by: David Rientjes <rientjes@...gle.com>
> ---
>  arch/x86/kvm/svm.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -6799,7 +6799,8 @@ static int sev_dbg_crypt(struct kvm *kvm, struct kvm_sev_cmd *argp, bool dec)
>  	struct page **src_p, **dst_p;
>  	struct kvm_sev_dbg debug;
>  	unsigned long n;
> -	int ret, size;
> +	unsigned int size;
> +	int ret;
>  
>  	if (!sev_guest(kvm))
>  		return -ENOTTY;
> @@ -6807,6 +6808,11 @@ static int sev_dbg_crypt(struct kvm *kvm, struct kvm_sev_cmd *argp, bool dec)
>  	if (copy_from_user(&debug, (void __user *)(uintptr_t)argp->data, sizeof(debug)))
>  		return -EFAULT;
>  
> +	if (!debug.len || debug.src_uaddr + debug.len < debug.src_uaddr)
> +		return -EINVAL;
> +	if (!debug.dst_uaddr)
> +		return -EINVAL;
> +
>  	vaddr = debug.src_uaddr;
>  	size = debug.len;
>  	vaddr_end = vaddr + size;
> @@ -6857,8 +6863,8 @@ static int sev_dbg_crypt(struct kvm *kvm, struct kvm_sev_cmd *argp, bool dec)
>  						     dst_vaddr,
>  						     len, &argp->error);
>  
> -		sev_unpin_memory(kvm, src_p, 1);
> -		sev_unpin_memory(kvm, dst_p, 1);
> +		sev_unpin_memory(kvm, src_p, n);
> +		sev_unpin_memory(kvm, dst_p, n);
>  
>  		if (ret)
>  			goto err;
> 

Queued, thanks.

Paolo