[alsa-devel] [patch] ALSA: compress: fix an integer overflow check

[Takashi Iwai]

At Wed, 16 Jul 2014 09:37:04 +0300,
Dan Carpenter wrote:
> 
> I previously added an integer overflow check here but looking at it now,
> it's still buggy.
> 
> The bug happens in snd_compr_allocate_buffer().  We multiply
> ".fragments" and ".fragment_size" and that doesn't overflow but then we
> save it in an unsigned int so it truncates the high bits away and we
> allocate a smaller than expected size.
> 
> Fixes: b35cc8225845 ('ALSA: compress_core: integer overflow in snd_compr_allocate_buffer()')
> Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>
> ---
> The other option would be to declare buffer_size as size_t instead of
> an unsigned int.  This feels like a safer fix though.

Agreed, I took the patch now as is.  Thanks.


Takashi

> 
> diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
> index 7403f34..89028fa 100644
> --- a/sound/core/compress_offload.c
> +++ b/sound/core/compress_offload.c
> @@ -491,7 +491,7 @@ static int snd_compress_check_input(struct snd_compr_params *params)
>  {
>  	/* first let's check the buffer parameter's */
>  	if (params->buffer.fragment_size == 0 ||
> -			params->buffer.fragments > SIZE_MAX / params->buffer.fragment_size)
> +	    params->buffer.fragments > INT_MAX / params->buffer.fragment_size)
>  		return -EINVAL;
>  
>  	/* now codec parameters */
>