Re: [PATCH 3/3] KVM: PPC: Fix mmio length message

Excerpts from Fabiano Rosas's message of December 24, 2021 7:15 am:
> We check against 'bytes' but print 'run->mmio.len' which at that point
> has an old value.
> 
> e.g. 16-byte load:
> 
> before:
> __kvmppc_handle_load: bad MMIO length: 8
> 
> now:
> __kvmppc_handle_load: bad MMIO length: 16
> 
> Signed-off-by: Fabiano Rosas <[email protected]>

This patch fine, but in the case of overflow we continue anyway here.
Can that overwrite some other memory in the kvm_run struct?

This is familiar, maybe something Alexey has noticed in the past too?
What was the consensus on fixing it? (at least it should have a comment
if it's not a problem IMO)

Thanks,
Nick

> ---
>  arch/powerpc/kvm/powerpc.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 793d42bd6c8f..7823207eb8f1 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -1246,7 +1246,7 @@ static int __kvmppc_handle_load(struct kvm_vcpu *vcpu,
>  
>  	if (bytes > sizeof(run->mmio.data)) {
>  		printk(KERN_ERR "%s: bad MMIO length: %d\n", __func__,
> -		       run->mmio.len);
> +		       bytes);
>  	}
>  
>  	run->mmio.phys_addr = vcpu->arch.paddr_accessed;
> @@ -1335,7 +1335,7 @@ int kvmppc_handle_store(struct kvm_vcpu *vcpu,
>  
>  	if (bytes > sizeof(run->mmio.data)) {
>  		printk(KERN_ERR "%s: bad MMIO length: %d\n", __func__,
> -		       run->mmio.len);
> +		       bytes);
>  	}
>  
>  	run->mmio.phys_addr = vcpu->arch.paddr_accessed;
> -- 
> 2.33.1
> 
>