[Mesa-dev] [PATCH] glsl/blob: clear padding bytes

[Grazvydas Ignotas]

(CCing some people who touched or reviewed blob)
Ping. I think writing stale heap contents to cache should be avoided
and this patch is an improvement.

Gražvydas

On Fri, Mar 3, 2017 at 1:59 AM, Grazvydas Ignotas <notasas at gmail.com> wrote:
> Since blob is intended for serializing data, it's not a good idea to
> leave padding holes with uninitialized data, which may leak heap
> contents and hurt compression if the blob is later compressed, like
> done by shader cache. Clear it.
>
> Signed-off-by: Grazvydas Ignotas <notasas at gmail.com>
> ---
> I don't know why blob bothers with aligning at all, maybe it's better
> to just get rid of it and replace *(uint *) reads with memcpy?
>
>  src/compiler/glsl/blob.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/src/compiler/glsl/blob.c b/src/compiler/glsl/blob.c
> index dd4341b..a7a5e65 100644
> --- a/src/compiler/glsl/blob.c
> +++ b/src/compiler/glsl/blob.c
> @@ -70,10 +70,13 @@ align_blob(struct blob *blob, size_t alignment)
>  {
>     const size_t new_size = ALIGN(blob->size, alignment);
>
> -   if (! grow_to_fit (blob, new_size - blob->size))
> -      return false;
> +   if (blob->size < new_size) {
> +      if (! grow_to_fit(blob, new_size - blob->size))
> +         return false;
>
> -   blob->size = new_size;
> +      memset(blob->data + blob->size, 0, new_size - blob->size);
> +      blob->size = new_size;
> +   }
>
>     return true;
>  }
> --
> 2.7.4
>