cmd: mtdparts: fix null pointer dereference in parse_mtdparts

In case there is no mtdparts variable in relocated environment,
NULL is assigned to p, which is later fed to strncpy.
Also function parameter mtdparts is completely ignored, so use it
in case mtdparts variable is not found in environment. This
parameter is checked not to be NULL in caller.

Signed-off-by: Ladislav Michl <ladis@linux-mips.org>

cmd/mtdparts.c

@@ -1524,7 +1524,7 @@ static int spread_partitions(void)
  */
 static int parse_mtdparts(const char *const mtdparts)
 {
-	const char *p = mtdparts;
+	const char *p;
 	struct mtd_device *dev;
 	int err = 1;
 	char tmp_parts[MTDPARTS_MAXLEN];
@@ -1538,20 +1538,25 @@ static int parse_mtdparts(const char *const mtdparts)
 	}
 
 	/* re-read 'mtdparts' variable, mtd_devices_init may be updating env */
-	if (gd->flags & GD_FLG_ENV_READY) {
+	if (gd->flags & GD_FLG_ENV_READY)
 		p = getenv("mtdparts");
-	} else {
-		p = tmp_parts;
-		getenv_f("mtdparts", tmp_parts, MTDPARTS_MAXLEN);
+	else {
+		if (getenv_f("mtdparts", tmp_parts, MTDPARTS_MAXLEN) != -1)
+			p = tmp_parts;
+		else
+			p = NULL;
 	}
 
+	if (!p)
+		p = mtdparts;
+
 	if (strncmp(p, "mtdparts=", 9) != 0) {
 		printf("mtdparts variable doesn't start with 'mtdparts='\n");
 		return err;
 	}
 	p += 9;
 
-	while (p && (*p != '\0')) {
+	while (*p != '\0') {
 		err = 1;
 		if ((device_parse(p, &p, &dev) != 0) || (!dev))
 			break;
@@ -1569,12 +1574,10 @@ static int parse_mtdparts(const char *const mtdparts)
 		list_add_tail(&dev->link, &devices);
 		err = 0;
 	}
-	if (err == 1) {
+	if (err == 1)
 		device_delall(&devices);
-		return 1;
-	}
 
-	return 0;
+	return err;
 }
 
 /**