msm: mdss: Handling possible integer overflow

fudge_factor calculation can suffer from integer overflow as numer and
denom are user controlled. Hence this change will first check for the
overflow and return immediately.

CRs-Fixed: 1110860
Change-Id: I3fab3edd4515d7a4c67f29d68b2039f234b03612
Signed-off-by: Harsh Sahu <hsahu@codeaurora.org>

drivers/video/fbdev/msm/mdss_mdp_ctl.c

@@ -73,8 +73,18 @@ static void __mdss_mdp_mixer_write_cfg(struct mdss_mdp_mixer *mixer,
 
 static inline u64 fudge_factor(u64 val, u32 numer, u32 denom)
 {
-	u64 result = (val * (u64)numer);
+	u64 result = val;
-	do_div(result, denom);
+
+	if (val) {
+		u64 temp = -1UL;
+
+		do_div(temp, val);
+		if (temp > numer) {
+			/* no overflow, so we can do the operation*/
+			result = (val * (u64)numer);
+			do_div(result, denom);
+		}
+	}
 	return result;
 }