linux-kernel - [PATCH] drm/msm/mdp4: Fix potential integer overflow on 32 bit multiply

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Message-Id: <20210929110804.210725-1-colin.king@canonical.com>
Date:   Wed, 29 Sep 2021 12:08:04 +0100
From:   Colin King <colin.king@...onical.com>
To:     Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...ux.ie>, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] drm/msm/mdp4: Fix potential integer overflow on 32 bit multiply

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

In the case where clock is 2147485 or greater the 32 bit multiplication
by 1000 will cause an integer overflow. Fix this by making the constant
1000 a long to ensure a long multiply occurs to avoid the overflow
before assigning the result to the long result in variable requested.
Most probably a theoretical overflow issue, but worth fixing.

Addresses-Coverity: ("Unintentional integer overflow")
Fixes: 3e87599b68e7 ("drm/msm/mdp4: add LVDS panel support")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c b/drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c
index 7288041dd86a..deada745d5b9 100644
--- a/drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c
+++ b/drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c
@@ -64,7 +64,7 @@ static int mdp4_lvds_connector_mode_valid(struct drm_connector *connector,
 	struct drm_encoder *encoder = mdp4_lvds_connector->encoder;
 	long actual, requested;
 
-	requested = 1000 * mode->clock;
+	requested = 1000L * mode->clock;
 	actual = mdp4_lcdc_round_pixclk(encoder, requested);
 
 	DBG("requested=%ld, actual=%ld", requested, actual);
-- 
2.32.0