Re: [PATCH] KVM: apic: avoid calculating pending eoi from an uninitialized val

[Vitaly Kuznetsov]

linmiaohe <linmiaohe@xxxxxxxxxx> writes:

> From: Miaohe Lin <linmiaohe@xxxxxxxxxx>
>
> When get user eoi value failed, var val would be uninitialized and result
> in calculating pending eoi from an uninitialized val. Initialize var val
> to 0 to fix this case.

Let me try to suggest an alternative wording,

"When pv_eoi_get_user() fails, 'val' may remain uninitialized and the
return value of pv_eoi_get_pending() becomes random. Fix the issue by
initializing the variable."

>
> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> ---
>  arch/x86/kvm/lapic.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 4f14ec7525f6..7e77e94f3176 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -626,7 +626,7 @@ static inline bool pv_eoi_enabled(struct kvm_vcpu *vcpu)
>  
>  static bool pv_eoi_get_pending(struct kvm_vcpu *vcpu)
>  {
> -	u8 val;
> +	u8 val = 0;
>  	if (pv_eoi_get_user(vcpu, &val) < 0)
>  		printk(KERN_WARNING "Can't read EOI MSR value: 0x%llx\n",
>  			   (unsigned long long)vcpu->arch.pv_eoi.msr_val);

Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>

But why compilers don't complain?

-- 
Vitaly