Re: [PATCH] KVM: x86: fix for missing initialization of return status variable

From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Ameer Hamza <amhamza.mgc@gmail.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	amhamza.mgc@gmail.com, pbonzini@redhat.com, seanjc@google.com,
	wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org,
	tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
	dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com
Subject: Re: [PATCH] KVM: x86: fix for missing initialization of return status variable
Date: Mon, 06 Dec 2021 10:06:26 +0100	[thread overview]
Message-ID: <87ee6q6r1p.fsf@redhat.com> (raw)
In-Reply-To: <20211205194719.16987-1-amhamza.mgc@gmail.com>

Ameer Hamza <amhamza.mgc@gmail.com> writes:

> If undefined ioctl number is passed to the kvm_vcpu_ioctl_device_attr
> function, it should return with error status.
>
> Addresses-Coverity: 1494124 ("Uninitialized scalar variable")
>
> Signed-off-by: Ameer Hamza <amhamza.mgc@gmail.com>
> ---
>  arch/x86/kvm/x86.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index e0aa4dd53c7f..55b90c185717 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5001,7 +5001,7 @@ static int kvm_vcpu_ioctl_device_attr(struct kvm_vcpu *vcpu,
>  				      void __user *argp)
>  {
>  	struct kvm_device_attr attr;
> -	int r;
> +	int r = -EINVAL;
>  
>  	if (copy_from_user(&attr, argp, sizeof(attr)))
>  		return -EFAULT;

The reported issue is not real, kvm_vcpu_ioctl_device_attr() is never
called with anything but [KVM_HAS_DEVICE_ATTR, KVM_GET_DEVICE_ATTR,
KVM_SET_DEVICE_ATTR] as 'ioctl' and the switch below covers all
three. Instead of initializing 'r' we could've added a 'default' case to
the switch, either returning something like EINVAL or just BUG(). Hope
it'll silence coverity.

-- 
Vitaly