[Mesa-dev] [PATCH 2/4] mesa: Set the correct image size in _mesa_validate_pbo_access()

[Laura Ekstrand]

Reviewed-by: Laura Ekstrand <laura at jlekstrand.net>

On Thu, Mar 5, 2015 at 12:20 AM, Eduardo Lima Mitev <elima at igalia.com>
wrote:

> _mesa_validate_pbo_access() provides a generic way to check that a
> requested pixel transfer operation on a PBO falls within the
> boundaries of the buffer. It is used in various other places, and
> depending on the caller, some arguments are used or not.
>
> In particular, the 'clientMemSize' argument is used only by calls
> that are knowledgeable of the total size of the user data involved
> in a pixel transfer, such as the case of compressed texture image
> calls. Other calls don't provide 'clientMemSize' directly since it
> is made implicit from the size and format of the texture, and its
> data type. In these cases, a sufficiently big value is passed to
> 'clientMemSize' (INT_MAX) to avoid an incorrect constrain.
>
> The problem is that _mesa_validate_pbo_access() use uint
> pointers to make the calculations, which are 64 bits long in 64
> bits platforms, meanwhile the dummy INT_MAX passed in 'clientMemSize'
> is just 32 bits. This causes a constrain that is not desired.
>
> This patch fixes that by checking that if 'clientMemSize' is MAX_INT,
> then UINTPTR_MAX is assumed instead.
>
> This is an ugly workaround to the fact that _mesa_validate_pbo_access()
> intends to be a one function fits all. The clean solution here would
> be to break it into different functions that provide the adequate API
> for each of the possible code paths and validation needs.
>
> Since there are callers relying on passing INT_MAX to 'clientMemSize',
> this patch is necessary to deal with the problem above while a cleaner
> implementation of the PBO API is not implemented.
> ---
>  src/mesa/main/pbo.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/src/mesa/main/pbo.c b/src/mesa/main/pbo.c
> index 5c906ed..259f763 100644
> --- a/src/mesa/main/pbo.c
> +++ b/src/mesa/main/pbo.c
> @@ -80,7 +80,7 @@ _mesa_validate_pbo_access(GLuint dimensions,
>      */
>     if (!_mesa_is_bufferobj(pack->BufferObj)) {
>        offset = 0;
> -      size = clientMemSize;
> +      size = (clientMemSize == INT_MAX) ? UINTPTR_MAX : clientMemSize;
>     } else {
>        offset = (uintptr_t)ptr;
>        size = pack->BufferObj->Size;
> --
> 2.1.3
>
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