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From:   Tzung-Bi Shih <tzungbi@google.com>
Date:   Fri, 4 Dec 2020 16:57:45 +0800
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Subject: Re: [PATCH] [v2] ASoC: cros_ec_codec: fix uninitialized memory read
To:     Arnd Bergmann <arnd@kernel.org>
Cc:     Cheng-Yi Chiang <cychiang@chromium.org>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        Jaroslav Kysela <perex@perex.cz>,
        Takashi Iwai <tiwai@suse.com>,
        Benson Leung <bleung@chromium.org>,
        Enric Balletbo i Serra <enric.balletbo@collabora.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Guenter Roeck <groeck@chromium.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Ard Biesheuvel <ardb@kernel.org>,
        Eric Biggers <ebiggers@google.com>,
        Yu-Hsuan Hsu <yuhsuan@chromium.org>,
        Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>,
        ALSA development <alsa-devel@alsa-project.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Fri, Dec 4, 2020 at 4:36 PM Arnd Bergmann <arnd@kernel.org> wrote:
> diff --git a/sound/soc/codecs/cros_ec_codec.c b/sound/soc/codecs/cros_ec_codec.c
> index 58894bf47514..6ec673573c70 100644
> --- a/sound/soc/codecs/cros_ec_codec.c
> +++ b/sound/soc/codecs/cros_ec_codec.c
> @@ -348,7 +348,7 @@ static int i2s_rx_event(struct snd_soc_dapm_widget *w,
>         }
>
>         return send_ec_host_command(priv->ec_device, EC_CMD_EC_CODEC_I2S_RX,
> -                                   (uint8_t *)&p, sizeof(p), NULL, 0);
> +                                   &p.cmd, sizeof(p.cmd), NULL, 0);
>  }

I would prefer your v1.

Reasons:
1. The change is not just kernel related.
There is a EC (embedded controller) firmware to collaborate with the
code.  The firmware doesn't know the kernel only copies the first byte
of the packet (at least for now).  See
https://chromium.googlesource.com/chromiumos/platform/ec/+/refs/heads/master/common/audio_codec_i2s_rx.c#120.

2. We don't copy partial packets in a EC host command.
IMHO, it is also not a big deal if copying a few unused bytes in the packet.