Re: [PATCH] kvm: Ensure writes to the coalesced MMIO ring are within bounds

[Paolo Bonzini]

On 18/09/19 15:59, Will Deacon wrote:
> Okey doke, as long as it gets fixed! My minor concerns with the error-checking
> variant are:
> 
>   * Whether or not you need a READ_ONCE to prevent the compiler potentially
>     reloading 'ring->last' after validation

Yes, it certainly needs READ_ONCE.  I had already added it locally, indeed.

>   * Whether or not this could be part of a spectre-v1 gadget

I think not, the spectrev1 gadget require a load that is indexed from
the contents of ring->coalesced_mmio[insert], but there's none.

Paolo

> so, given that I don't think the malicious host deserves an error code if it
> starts writing the 'last' index, I went with the "obviously safe" version.
> But up to you.
> 
> Will
>