[alsa-devel] [patch] ALSA: seq: potential out of bounds in do_control()

[Takashi Iwai]

At Wed, 11 Feb 2015 18:10:54 +0300,
Dan Carpenter wrote:
> 
> Smatch complains that "control" is user specifigy and needs to be
> capped.  The call tree to understand this warning is quite long.
> 
> snd_seq_write()  <-- get the event from the user
>   snd_seq_client_enqueue_event()
>     snd_seq_deliver_event()
>       deliver_to_subscribers()
>         snd_seq_deliver_single_event()
>           snd_opl3_oss_event_input()
>             snd_midi_process_event()
>               do_control()
> 
> Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>
> ---
> I have spent some time reviewing this code, but I may have missed
> something where we verify that control is in bounds.  I'm not very
> familiar with this code and the call tree is fairly long.

I applied locally now and will merge it later once when the current
pull request is resolved.


thanks,

Takashi

> 
> diff --git a/sound/core/seq/seq_midi_emul.c b/sound/core/seq/seq_midi_emul.c
> index 9b6470c..7ba9373 100644
> --- a/sound/core/seq/seq_midi_emul.c
> +++ b/sound/core/seq/seq_midi_emul.c
> @@ -269,6 +269,9 @@ do_control(struct snd_midi_op *ops, void *drv, struct snd_midi_channel_set *chse
>  {
>  	int  i;
>  
> +	if (control >= ARRAY_SIZE(chan->control))
> +		return;
> +
>  	/* Switches */
>  	if ((control >=64 && control <=69) || (control >= 80 && control <= 83)) {
>  		/* These are all switches; either off or on so set to 0 or 127 */
>