Re: [Xen-devel] [alsa-devel] [PATCH 3/3] ALSA: xen-front: Use Xen common shared buffer implementation

[Takashi Iwai <tiwai@xxxxxxx>]

On Thu, 22 Nov 2018 11:02:30 +0100,
Oleksandr Andrushchenko wrote:
> 
> @@ -214,12 +221,19 @@ static void stream_clear(struct 
> xen_snd_front_pcm_stream_info *stream)
>       stream->out_frames = 0;
>       atomic_set(&stream->hw_ptr, 0);
>       xen_snd_front_evtchnl_pair_clear(stream->evt_pair);
> -     xen_snd_front_shbuf_clear(&stream->sh_buf);
> +     memset(&stream->shbuf, 0, sizeof(stream->shbuf));
> +     stream->buffer = NULL;
> +     stream->buffer_sz = 0;
> +     stream->pages = NULL;
> +     stream->num_pages = 0;
>  }
>  
>  static void stream_free(struct xen_snd_front_pcm_stream_info *stream)
>  {
> -     xen_snd_front_shbuf_free(&stream->sh_buf);
> +     xen_front_pgdir_shbuf_unmap(&stream->shbuf);
> +     xen_front_pgdir_shbuf_free(&stream->shbuf);
> +     free_pages_exact(stream->buffer, stream->buffer_sz);
> +     kfree(stream->pages);
>       stream_clear(stream);
>  }
>  
> @@ -421,10 +435,34 @@ static int alsa_close(struct snd_pcm_substream 
> *substream)
>       return 0;
>  }
>  
> +static int shbuf_setup_backstore(struct xen_snd_front_pcm_stream_info 
> *stream,
> +                              size_t buffer_sz)
> +{
> +     int i;
> +
> +     stream->buffer_sz = buffer_sz;
> +     stream->buffer = alloc_pages_exact(stream->buffer_sz, GFP_KERNEL);
> +     if (!stream->buffer)
> +             return -ENOMEM;

This keeps the NULL stream->buffer, and then the caller goes to the
error path via stream_free() which will lead to an Oops due to the
unconditional call of free_pages_exact().


thanks,

Takashi

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