lkml.org 
[lkml]   [2020]   [Sep]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] drm/rockchip: cdn-dp: fix sign extension on an int multiply for a u64 result
Date
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>
---
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
\
 
 \ /
  Last update: 2020-09-16 00:28    [W:0.024 / U:2.528 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site