On Tue, Sep 15, 2020 at 9:20 AM Colin King colin.king@canonical.com wrote:

From: Colin Ian King colin.king@canonical.com

The variable bit_per_pix is a u8 and is promoted in the multiplication to an int type and then sign extended to a u64. If the result of the int multiplication is greater than 0x7fffffff then the upper 32 bits will be set to 1 as a result of the sign extension. Avoid this by casting tu_size_reg to u64 to avoid sign extension and also a potential overflow.

Addresses-Coverity: ("Unintended sign extension") Fixes: 1a0f7ed3abe2 ("drm/rockchip: cdn-dp: add cdn DP support for rk3399") Signed-off-by: Colin Ian King colin.king@canonical.com

Reviewed-by: Guenter Roeck groeck@chromium.org

---

drivers/gpu/drm/rockchip/cdn-dp-reg.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/rockchip/cdn-dp-reg.c b/drivers/gpu/drm/rockchip/cdn-dp-reg.c index 9d2163ef4d6e..33fb4d05c506 100644 --- a/drivers/gpu/drm/rockchip/cdn-dp-reg.c +++ b/drivers/gpu/drm/rockchip/cdn-dp-reg.c @@ -658,7 +658,7 @@ int cdn_dp_config_video(struct cdn_dp_device *dp) */ do { tu_size_reg += 2;

•           symbol = tu_size_reg * mode->clock * bit_per_pix;
  

•           symbol = (u64)tu_size_reg * mode->clock * bit_per_pix;
            do_div(symbol, dp->max_lanes * link_rate * 8);
            rem = do_div(symbol, 1000);
            if (tu_size_reg > 64) {
  

-- 2.27.0