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

John Keeping
2017-01-30T18:16:36Z

On Mon, 30 Jan 2017 13:01:46 -0500, Sean Paul wrote:

> 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@metanate.com>
> > Reviewed-by: Chris Zhong <zyw@rock-chips.com>
> > ---
> > 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.

Won't that mask off the data written by "tx_buf[1] << 8"?