Re: [PATCH v3 06/24] drm/rockchip: dw-mipi-dsi: avoid out-of-bounds read on tx_buf

[Sean Paul]

On Sun, Jan 29, 2017 at 01:24:26PM +0000, John Keeping wrote:
> As a side-effect of this, encode the endianness explicitly rather than
> casting a u16.
> 
> Signed-off-by: John Keeping <john@xxxxxxxxxxxx>
> Reviewed-by: Chris Zhong <zyw@xxxxxxxxxxxxxx>
> ---
> v3:
> - Add Chris' Reviewed-by
> Unchanged in v2
> 
>  drivers/gpu/drm/rockchip/dw-mipi-dsi.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
> index 4be1ff3a42bb..2e6ad4591ebf 100644
> --- a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
> +++ b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
> @@ -572,8 +572,13 @@ static int dw_mipi_dsi_gen_pkt_hdr_write(struct dw_mipi_dsi *dsi, u32 hdr_val)
>  static int dw_mipi_dsi_dcs_short_write(struct dw_mipi_dsi *dsi,
>  				       const struct mipi_dsi_msg *msg)
>  {
> -	const u16 *tx_buf = msg->tx_buf;
> -	u32 val = GEN_HDATA(*tx_buf) | GEN_HTYPE(msg->type);
> +	const u8 *tx_buf = msg->tx_buf;
> +	u32 val = GEN_HTYPE(msg->type);
> +
> +	if (msg->tx_len > 0)
> +		val |= GEN_HDATA(tx_buf[0]);
> +	if (msg->tx_len > 1)
> +		val |= GEN_HDATA(tx_buf[1] << 8);

You should probably update the mask inside GEN_HDATA to mask off 8 bits instead of
16.

Sean

>  
>  	if (msg->tx_len > 2) {
>  		dev_err(dsi->dev, "too long tx buf length %zu for short write\n",
> -- 
> 2.11.0.197.gb556de5.dirty
> 
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-- 
Sean Paul, Software Engineer, Google / Chromium OS