[media] v4l2-dv-timings: add sanity checks in cvt,gtf calculations

Wrong values of hfreq and image height can lead to strange timings.
Avoid timing calculations for such values.

Suggested By: Martin Bugge <marbugge@cisco.com>

Cc: Martin Bugge <marbugge@cisco.com>
Signed-off-by: Prashant Laddha <prladdha@cisco.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/v4l2-core/v4l2-dv-timings.c

@@ -365,6 +365,9 @@ bool v4l2_detect_cvt(unsigned frame_height, unsigned hfreq, unsigned vsync,
 	else
 		return false;
 
+	if (hfreq == 0)
+		return false;
+
 	/* Vertical */
 	if (reduced_blanking) {
 		v_fp = CVT_RB_V_FPORCH;
@@ -382,6 +385,9 @@ bool v4l2_detect_cvt(unsigned frame_height, unsigned hfreq, unsigned vsync,
 	}
 	image_height = (frame_height - v_fp - vsync - v_bp + 1) & ~0x1;
 
+	if (image_height < 0)
+		return false;
+
 	/* Aspect ratio based on vsync */
 	switch (vsync) {
 	case 4:
@@ -527,12 +533,18 @@ bool v4l2_detect_gtf(unsigned frame_height,
 	else
 		return false;
 
+	if (hfreq == 0)
+		return false;
+
 	/* Vertical */
 	v_fp = GTF_V_FP;
 
 	v_bp = (GTF_MIN_VSYNC_BP * hfreq + 500000) / 1000000 - vsync;
 	image_height = (frame_height - v_fp - vsync - v_bp + 1) & ~0x1;
 
+	if (image_height < 0)
+		return false;
+
 	if (aspect.numerator == 0 || aspect.denominator == 0) {
 		aspect.numerator = 16;
 		aspect.denominator = 9;