Re: [PATCH v6 6/6] KVM: arm64: Ensure FFA ranges are page aligned

[Sebastian Ene <sebastianene@google.com>]

On Wed, May 27, 2026 at 03:02:36PM +0000, Mostafa Saleh wrote:

Hi Mostafa,

> At the moment we only check that the size of the range is page
> aligned, and truncate the address to the page boundary.
> This make an assumption that TZ will do the same.
> 
> However, it might decide to use the extra offset of the neighbour
> page at the end, which is valid under FFA if NS is using larger
> page size.
> 
> Harden this check by also checking that the base address is aligned
> and reject it otherwise.
> 
> Fixes: 436090001776 ("KVM: arm64: Handle FFA_MEM_SHARE calls from the host")
> Signed-off-by: Mostafa Saleh <smostafa@google.com>
> ---
>  arch/arm64/kvm/hyp/nvhe/ffa.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> index a12e01883314..daf0e328c847 100644
> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> @@ -352,7 +352,7 @@ static u32 __ffa_host_share_ranges(struct ffa_mem_region_addr_range *ranges,
>  		u64 sz = (u64)range->pg_cnt * FFA_PAGE_SIZE;
>  		u64 pfn = hyp_phys_to_pfn(range->address);
>  
> -		if (!PAGE_ALIGNED(sz))
> +		if (!PAGE_ALIGNED(sz | range->address))
>  			break;
>  

Should we do the pfn assignment after the check ?

>  		if (__pkvm_host_share_ffa(pfn, sz / PAGE_SIZE))
> @@ -372,7 +372,7 @@ static u32 __ffa_host_unshare_ranges(struct ffa_mem_region_addr_range *ranges,
>  		u64 sz = (u64)range->pg_cnt * FFA_PAGE_SIZE;
>  		u64 pfn = hyp_phys_to_pfn(range->address);
>  
> -		if (!PAGE_ALIGNED(sz))
> +		if (!PAGE_ALIGNED(sz | range->address))
>  			break;
>  

The same here

>  		if (__pkvm_host_unshare_ffa(pfn, sz / PAGE_SIZE))
> -- 
> 2.54.0.746.g67dd491aae-goog
> 

Thanks,
Sebastian