On Thu, Feb 20, 2020 at 05:33:17PM +0100, Vitaly Kuznetsov wrote:
> 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;
Rather than initialize @val, I'd prefer to explicitly handle the error,
similar to pv_eoi_clr_pending() and pv_eoi_set_pending(), e.g.
u8 val;
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);
return false;
}
return val & 0x1;
> > 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?
Clang might?
