Re: [PATCH] KVM: arm64: Fix 64 bit mmio handle

[Schspa Shi]

Marc Zyngier <maz@xxxxxxxxxx> writes:

> > I have running some static code analysis software upon Kernel 
> > code.
> > Seeing there is possible overflow.
> >
> > maks << 1U << ((len * 8) -1);
> >
> > The AI don't know, len is only the value of 1, 2, 4, and make 
> > this
> > a warnings
> >
> > I tring to analysis this, but didn't realize the real scenario 
> > of
> > sign extension, and finally sent this problematic patch.
> >
> > I do see some uninitialized memory reads (the values are not 
> > used
> > in the end, just as temporary space for API execution),
> > do we need to fix these?
>
> You need to be more descriptive here. What uninitialised reads? 
> In
> general, pointing at the code and providing a full description 
> of what
> you think is incorrect would really help...
>
> 	M.
One example is
int vgic_v3_has_attr_regs(struct kvm_device *dev, struct 
kvm_device_attr *attr)
{
	...
   case KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS: {
		u64 reg, id;

		id = (attr->attr & KVM_DEV_ARM_VGIC_SYSREG_INSTR_MASK);
		return vgic_v3_has_cpu_sysregs_attr(vcpu, 0, id, &reg);
	}

}

The funcion vgic_v3_has_cpu_sysregs_attr will read reg's value to
params without initialization. There should have no problems,
because the register value never used.

--
BRs
Schspa Shi