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Subject: Re: [PATCH] KVM: Use vmemdup_user()
To:     Denis Efremov <efremov@linux.com>
Cc:     joe@perches.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org
References: <0c00d96c46d34d69f5f459baebf3c89a507730fc.camel@perches.com>
 <20200603101131.2107303-1-efremov@linux.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <eb48b6d2-6189-945d-33e2-1f5b29338d96@redhat.com>
Date:   Thu, 4 Jun 2020 20:41:12 +0200
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On 03/06/20 12:11, Denis Efremov wrote:
> Replace opencoded alloc and copy with vmemdup_user().
> 
> Signed-off-by: Denis Efremov <efremov@linux.com>
> ---
> Looks like these are the only places in KVM that are suitable for
> vmemdup_user().
> 
>  arch/x86/kvm/cpuid.c | 17 +++++++----------
>  virt/kvm/kvm_main.c  | 19 ++++++++-----------
>  2 files changed, 15 insertions(+), 21 deletions(-)
> 
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 901cd1fdecd9..27438a2bdb62 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -182,17 +182,14 @@ int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
>  	r = -E2BIG;
>  	if (cpuid->nent > KVM_MAX_CPUID_ENTRIES)
>  		goto out;
> -	r = -ENOMEM;
>  	if (cpuid->nent) {
> -		cpuid_entries =
> -			vmalloc(array_size(sizeof(struct kvm_cpuid_entry),
> -					   cpuid->nent));
> -		if (!cpuid_entries)
> -			goto out;
> -		r = -EFAULT;
> -		if (copy_from_user(cpuid_entries, entries,
> -				   cpuid->nent * sizeof(struct kvm_cpuid_entry)))
> +		cpuid_entries = vmemdup_user(entries,
> +					     array_size(sizeof(struct kvm_cpuid_entry),
> +							cpuid->nent));
> +		if (IS_ERR(cpuid_entries)) {
> +			r = PTR_ERR(cpuid_entries);
>  			goto out;
> +		}
>  	}
>  	for (i = 0; i < cpuid->nent; i++) {
>  		vcpu->arch.cpuid_entries[i].function = cpuid_entries[i].function;
> @@ -212,8 +209,8 @@ int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
>  	kvm_x86_ops.cpuid_update(vcpu);
>  	r = kvm_update_cpuid(vcpu);
>  
> +	kvfree(cpuid_entries);
>  out:
> -	vfree(cpuid_entries);
>  	return r;
>  }
>  
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 731c1e517716..46a3743e95ff 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -3722,21 +3722,18 @@ static long kvm_vm_ioctl(struct file *filp,
>  		if (routing.flags)
>  			goto out;
>  		if (routing.nr) {
> -			r = -ENOMEM;
> -			entries = vmalloc(array_size(sizeof(*entries),
> -						     routing.nr));
> -			if (!entries)
> -				goto out;
> -			r = -EFAULT;
>  			urouting = argp;
> -			if (copy_from_user(entries, urouting->entries,
> -					   routing.nr * sizeof(*entries)))
> -				goto out_free_irq_routing;
> +			entries = vmemdup_user(urouting->entries,
> +					       array_size(sizeof(*entries),
> +							  routing.nr));
> +			if (IS_ERR(entries)) {
> +				r = PTR_ERR(entries);
> +				goto out;
> +			}
>  		}
>  		r = kvm_set_irq_routing(kvm, entries, routing.nr,
>  					routing.flags);
> -out_free_irq_routing:
> -		vfree(entries);
> +		kvfree(entries);
>  		break;
>  	}
>  #endif /* CONFIG_HAVE_KVM_IRQ_ROUTING */
> 

Queued, thanks.

Paolo