On Wed, Mar 09, 2022 at 05:32:19PM +0800, Jiasheng Jiang wrote:
> On Wed, Mar 09, 2022 at 01:58:04AM +0800, Dan Carpenter wrote:
> > smatch warnings:
> > sound/soc/soc-compress.c:628 snd_soc_new_compress() error: we previously 
> > assumed 'codec_dai' could be null (see line 571)
> 
> > de2c6f98817fa5d Jiasheng Jiang     2021-10-15 @571          if (codec_dai) {
> > 
> > Can codec_dai be NULL?  This new code assumes so.
> 
> > aeb6fa0f15c71a1 Peng Donglin       2017-08-16 @628                          
> > rtd->dai_link->stream_name, codec_dai->name, num);
> >                                                                             
> >                         ^^^^^^^^^^^^^^^^
> > Unchecked dereference
> 
> Actually, if 'codec_dai' is NULL, the check in line 584 will fail and return 
> -EINVAL.
> 
> a1068045883ed4a Vinod Koul         2016-01-07  584    if (playback + capture 
> != 1) {
> 141dfc9e3751f5f Charles Keepax     2018-01-26  585            
> dev_err(rtd->card->dev,
> 141dfc9e3751f5f Charles Keepax     2018-01-26  586                    
> "Compress ASoC: Invalid direction for P %d, C %d\n",
> a1068045883ed4a Vinod Koul         2016-01-07  587                    
> playback, capture);
> a1068045883ed4a Vinod Koul         2016-01-07  588            return -EINVAL;
> a1068045883ed4a Vinod Koul         2016-01-07  589    }
> 

Yeah.  That's true.  Smatch tries to look at conditions and figure out
the implications but this one is too complicated.

But if codec_dai can really be NULL then it would be easier to
understand if we reversed the check on codec_dai and returned early.

        if (!codec_dai) {
                dev_err(rtd->card->dev, "Missing codec\n");
                return -EINVAL;
        }

        /* check client and interface hw capabilities */
        if (snd_soc_dai_stream_valid(codec_dai, SNDRV_PCM_STREAM_PLAYBACK) &&
            snd_soc_dai_stream_valid(cpu_dai,   SNDRV_PCM_STREAM_PLAYBACK))
                playback = 1;

regards,
dan carpenter
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