From: Colin Ian King Date: Tue, 15 Sep 2020 16:20:49 +0000 (+0100) Subject: drm/rockchip: cdn-dp: fix sign extension on an int multiply for a u64 result X-Git-Tag: v5.10.79~3039 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=eee0f7d399b683d856ff5b1b2627306ec32f703e;p=platform%2Fkernel%2Flinux-rpi.git drm/rockchip: cdn-dp: fix sign extension on an int multiply for a u64 result [ Upstream commit ce0cb93a5adb283f577cd4661f511047b5e39028 ] 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. Fixes: 1a0f7ed3abe2 ("drm/rockchip: cdn-dp: add cdn DP support for rk3399") Signed-off-by: Colin Ian King Reviewed-by: Guenter Roeck Signed-off-by: Heiko Stuebner Link: https://patchwork.freedesktop.org/patch/msgid/20200915162049.36434-1-colin.king@canonical.com Signed-off-by: Sasha Levin --- diff --git a/drivers/gpu/drm/rockchip/cdn-dp-reg.c b/drivers/gpu/drm/rockchip/cdn-dp-reg.c index 9d2163e..33fb4d0 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) {