Re: [Xen-devel] [PATCH v5 6/7] xen/arm: don't iomem_permit_access for reserved-memory regions

[Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>]

Stefano Stabellini writes:

> Don't allow reserved-memory regions to be remapped into any unprivileged
> guests, until reserved-memory regions are properly supported in Xen. For
> now, do not call iomem_permit_access on them, because giving
> iomem_permit_access to dom0 means that the toolstack will be able to
> assign the region to a domU.
>
> Signed-off-by: Stefano Stabellini <stefanos@xxxxxxxxxx>
> ---
>
> Changes in v5:
> - fix check condition
> - use strnicmp
> - return error
> - improve commit message
>
> Changes in v4:
> - compare the parent name with reserved-memory
> - use dt_node_cmp
>
> Changes in v3:
> - new patch
> ---
>  xen/arch/arm/domain_build.c | 24 ++++++++++++++++--------
>  1 file changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index 4c8404155a..e0c0c01c88 100644
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -1155,15 +1155,23 @@ static int __init map_range_to_domain(const struct 
> dt_device_node *dev,
>      bool need_mapping = !dt_device_for_passthrough(dev);
>      int res;
>  
> -    res = iomem_permit_access(d, paddr_to_pfn(addr),
> -                              paddr_to_pfn(PAGE_ALIGN(addr + len - 1)));
> -    if ( res )
> +    /*
> +     * Don't give iomem permissions for reserved-memory ranges to domUs
> +     * until reserved-memory support is complete.
> +     */
> +    if ( strnicmp(dt_node_full_name(dev), "/reserved-memory",
> +         strlen("/reserved-memory")) != 0 )
Why are you using strnicmp there? With such usage it is the same as
strcasecmp(). But, if you want to find "/reserved-memory" anywhere in
dt_node_full_name(dev), then you probably want to use strcasestr()


>      {
> -        printk(XENLOG_ERR "Unable to permit to dom%d access to"
> -               " 0x%"PRIx64" - 0x%"PRIx64"\n",
> -               d->domain_id,
> -               addr & PAGE_MASK, PAGE_ALIGN(addr + len) - 1);
> -        return res;
> +        res = iomem_permit_access(d, paddr_to_pfn(addr),
> +                paddr_to_pfn(PAGE_ALIGN(addr + len - 1)));
> +        if ( res )
> +        {
> +            printk(XENLOG_ERR "Unable to permit to dom%d access to"
> +                    " 0x%"PRIx64" - 0x%"PRIx64"\n",
> +                    d->domain_id,
> +                    addr & PAGE_MASK, PAGE_ALIGN(addr + len) - 1);
> +            return res;
> +        }
>      }
>  
>      if ( need_mapping )


-- 
Volodymyr Babchuk at EPAM
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