[PATCH 5.8 171/633] drm/amd/display: fix potential integer overflow when shifting 32 bit variable bl_pwm

Greg Kroah-Hartman
2020-10-27T17:18:31Z

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

[ Upstream commit 1d5503331b12a76266049289747dfd94f1643fde ]

The 32 bit unsigned integer bl_pwm is being shifted using 32 bit arithmetic
and then being assigned to a 64 bit unsigned integer. There is a potential
for a 32 bit overflow so cast bl_pwm to enforce a 64 bit shift operation
to avoid this.

Addresses-Coverity: ("unintentional integer overflow")
Fixes: 3ba01817365c ("drm/amd/display: Move panel_cntl specific register from abm to panel_cntl.")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/amd/display/dc/dce/dce_panel_cntl.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dce/dce_panel_cntl.c b/drivers/gpu/drm/amd/display/dc/dce/dce_panel_cntl.c
index ebff9b1e312e5..124c081a0f2ca 100644
--- a/drivers/gpu/drm/amd/display/dc/dce/dce_panel_cntl.c
+++ b/drivers/gpu/drm/amd/display/dc/dce/dce_panel_cntl.c
@@ -75,7 +75,7 @@ static unsigned int calculate_16_bit_backlight_from_pwm(struct dce_panel_cntl *d
else
bl_pwm &= 0xFFFF;

- current_backlight = bl_pwm << (1 + bl_int_count);
+ current_backlight = (uint64_t)bl_pwm << (1 + bl_int_count);

if (bl_period == 0)
bl_period = 0xFFFF;
--
2.25.1