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

On Mon, Jan 30, 2017 at 06:16:36PM +0000, John Keeping wrote:

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

quoted

On Sun, Jan 29, 2017 at 01:24:26PM +0000, John Keeping wrote:

quoted

As a side-effect of this, encode the endianness explicitly rather than
casting a u16.

Signed-off-by: John Keeping <redacted>
Reviewed-by: Chris Zhong <redacted>
---
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"?

I would move the shift outside the mask, ie:

val |= GEN_HDATA(tx_buf[1]) << 8;

Sean

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-- 
Sean Paul, Software Engineer, Google / Chromium OS