MIPS: Loongson: Fix potentially wrong string handling

This error was reported by cppcheck:
arch/mips/loongson/common/machtype.c:56: error: Dangerous usage of 'str' (strncpy doesn't always 0-terminate it)

If strncpy copied MACHTYPE_LEN bytes, the destination string str
was not terminated.

The patch adds one more byte to str and makes sure that this byte is
always 0.
Signed-off-by: Stefan Weil <weil@mail.berlios.de>
Cc: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: Arnaud Patard <apatard@mandriva.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/2053/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/loongson/common/machtype.c

@@ -41,7 +41,7 @@ void __weak __init mach_prom_init_machtype(void)
 
 void __init prom_init_machtype(void)
 {
-	char *p, str[MACHTYPE_LEN];
+	char *p, str[MACHTYPE_LEN + 1];
 	int machtype = MACH_LEMOTE_FL2E;
 
 	mips_machtype = LOONGSON_MACHTYPE;
@@ -53,6 +53,7 @@ void __init prom_init_machtype(void)
 	}
 	p += strlen("machtype=");
 	strncpy(str, p, MACHTYPE_LEN);
+	str[MACHTYPE_LEN] = '\0';
 	p = strstr(str, " ");
 	if (p)
 		*p = '\0';