Re: [RFC 5/8] s390x/pci: Fix memory_region_access_valid call

[Cornelia Huck]

On Wed,  9 Dec 2020 15:34:23 -0500
Matthew Rosato <mjrosato@linux.ibm.com> wrote:

> In pcistb_service_handler, a call is made to validate that the memory
> region can be accessed.  However, the call is made using the entire length
> of the pcistb operation, which can be larger than the allowed memory
> access size (8).  Since we already know that the provided buffer is a
> multiple of 8, fix the call to memory_region_access_valid to iterate
> over the memory region in the same way as the subsequent call to
> memory_region_dispatch_write.
> 
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> ---
>  hw/s390x/s390-pci-inst.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/s390x/s390-pci-inst.c b/hw/s390x/s390-pci-inst.c
> index b07ef2a..a5270d0 100644
> --- a/hw/s390x/s390-pci-inst.c
> +++ b/hw/s390x/s390-pci-inst.c
> @@ -795,9 +795,11 @@ static int pcistb_default(S390PCIBusDevice *pbdev, 
> S390CPU *cpu,
>      mr = s390_get_subregion(mr, offset, len);
>      offset -= mr->addr;
>  
> -    if (!memory_region_access_valid(mr, offset, len, true,
> -                                    MEMTXATTRS_UNSPECIFIED)) {
> -        return -EINVAL;
> +    for (i = 0; i < len / 8; i++) {
> +        if (!memory_region_access_valid(mr, offset + i * 8, 8, true,
> +                                        MEMTXATTRS_UNSPECIFIED)) {
> +            return -EINVAL;
> +        }
>      }
>  
>      if (s390_cpu_virt_mem_read(cpu, gaddr, ar, pbdev->pcistb_buf, len)) {

Hm, that looks like a fix that's applicable for the current code base
as well... do you want to split this out?