Re: [PATCH 1/2] ALSA: pcm: disallow linking stream to itself

[Takashi Iwai]

On Mon, 08 Jun 2020 12:06:32 +0200,
MichaÅ MirosÅaw wrote:
> 
> Prevent SNDRV_PCM_IOCTL_LINK linking stream to itself - the code
> can't handle it. Fixed commit is not where bug was introduced, but
> changes the context significantly.
> 
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 0888c321de70 ("pcm_native: switch to fdget()/fdput()")
> Signed-off-by: MichaÅ MirosÅaw <mirq-linux@xxxxxxxxxxxx>

Thanks for the fix.  Just a minor point:

> @@ -2166,6 +2166,12 @@ static int snd_pcm_link(struct snd_pcm_substream *substream, int fd)
>  	}
>  	pcm_file = f.file->private_data;
>  	substream1 = pcm_file->substream;
> +
> +	if (substream == substream1) {
> +		res = -EDEADLK;

We've never used this error code, hence it may confuse the user-space
side.  I'd use a more standard -EINVAL instead; the error is basically
an invalid argument, after all.


thanks,

Takashi