video: omap2: Use scnprintf() for avoiding potential buffer overflow

Since snprintf() returns the would-be-output size instead of the
actual output size, the succeeding calls may go beyond the given
buffer limit.  Fix it by replacing with scnprintf().
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200311093230.24900-3-tiwai@suse.de

drivers/video/fbdev/omap2/omapfb/omapfb-sysfs.c

@@ -147,11 +147,11 @@ static ssize_t show_overlays(struct device *dev,
 			if (ovl == fbdev->overlays[ovlnum])
 				break;
 
-		l += snprintf(buf + l, PAGE_SIZE - l, "%s%d",
+		l += scnprintf(buf + l, PAGE_SIZE - l, "%s%d",
 				t == 0 ? "" : ",", ovlnum);
 	}
 
-	l += snprintf(buf + l, PAGE_SIZE - l, "\n");
+	l += scnprintf(buf + l, PAGE_SIZE - l, "\n");
 
 	omapfb_unlock(fbdev);
 	unlock_fb_info(fbi);
@@ -328,11 +328,11 @@ static ssize_t show_overlays_rotate(struct device *dev,
 	lock_fb_info(fbi);
 
 	for (t = 0; t < ofbi->num_overlays; t++) {
-		l += snprintf(buf + l, PAGE_SIZE - l, "%s%d",
+		l += scnprintf(buf + l, PAGE_SIZE - l, "%s%d",
 				t == 0 ? "" : ",", ofbi->rotation[t]);
 	}
 
-	l += snprintf(buf + l, PAGE_SIZE - l, "\n");
+	l += scnprintf(buf + l, PAGE_SIZE - l, "\n");
 
 	unlock_fb_info(fbi);