Re: [PATCH v7 04/10] xen/memory: Add a vmtrace_buf resource type

[Jan Beulich <jbeulich@suse.com>]

On 21.01.2021 22:27, Andrew Cooper wrote:
> --- a/xen/common/memory.c
> +++ b/xen/common/memory.c
> @@ -1068,11 +1068,35 @@ static unsigned int resource_max_frames(const struct domain *d,
>      case XENMEM_resource_grant_table:
>          return gnttab_resource_max_frames(d, id);
>  
> +    case XENMEM_resource_vmtrace_buf:
> +        return d->vmtrace_frames;
> +
>      default:
>          return arch_resource_max_frames(d, type, id);
>      }
>  }
>  
> +static int acquire_vmtrace_buf(
> +    struct domain *d, unsigned int id, unsigned long frame,
> +    unsigned int nr_frames, xen_pfn_t mfn_list[])
> +{
> +    const struct vcpu *v = domain_vcpu(d, id);
> +    unsigned int i;
> +    mfn_t mfn;
> +
> +    if ( !v || !v->vmtrace.buf ||
> +         nr_frames > d->vmtrace_frames ||
> +         (frame + nr_frames) > d->vmtrace_frames )
> +        return -EINVAL;


I think that for this to guard against overflow, the first nr_frames
needs to be replaced by frame (as having the wider type), or else a
very large value of frame coming in will not yield the intended
-EINVAL. If you agree, with this changed,
Reviewed-by: Jan Beulich <jbeulich@suse.com>

Jan