sdio: fix read buffer overflow

Avoid buffer underrun when parsing an invalid CISTPL_VERS_1.
Signed-off-by: NRoel Kluin <roel.kluin@gmail.com>
Cc: David Vrabel <david.vrabel@csr.com>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/mmc/core/sdio_cis.c

@@ -40,7 +40,7 @@ static int cistpl_vers_1(struct mmc_card *card, struct sdio_func *func,
 			nr_strings++;
 	}
 
-	if (buf[i-1] != '\0') {
+	if (nr_strings < 4) {
 		printk(KERN_WARNING "SDIO: ignoring broken CISTPL_VERS_1\n");
 		return 0;
 	}