Re: [PATCH v19 QEMU 4/4] memory: Do not allow direct write access to rom_device regions

[Paolo Bonzini <pbonzini@redhat.com>]

On 10/04/20 05:41, Alexander Duyck wrote:
> From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> 
> According to the documentation in memory.h a ROM memory region will be
> backed by RAM for reads, but is supposed to go through a callback for
> writes. Currently we were not checking for the existence of the rom_device
> flag when determining if we could perform a direct write or not.
> 
> To correct that add a check to memory_region_is_direct so that if the
> memory region has the rom_device flag set we will return false for all
> checks where is_write is set.
> 
> Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> ---
>  include/exec/memory.h |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index 1614d9a02c0c..e000bd2f97b2 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -2351,8 +2351,8 @@ void address_space_write_cached_slow(MemoryRegionCache *cache,
>  static inline bool memory_access_is_direct(MemoryRegion *mr, bool is_write)
>  {
>      if (is_write) {
> -        return memory_region_is_ram(mr) &&
> -               !mr->readonly && !memory_region_is_ram_device(mr);
> +        return memory_region_is_ram(mr) && !mr->readonly &&
> +               !mr->rom_device && !memory_region_is_ram_device(mr);
>      } else {
>          return (memory_region_is_ram(mr) && !memory_region_is_ram_device(mr)) ||
>                 memory_region_is_romd(mr);
> 

Good catch.  I queued this up for 5.0.

Thanks,

Paolo