mmc: read ext_csd version number

Make sure we do not try to parse a structure we do not
understand.
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

drivers/mmc/core/mmc.c

@@ -161,6 +161,7 @@ static int mmc_read_ext_csd(struct mmc_card *card)
 {
 	int err;
 	u8 *ext_csd;
+	unsigned int ext_csd_struct;
 
 	BUG_ON(!card);
 
@@ -209,6 +210,14 @@ static int mmc_read_ext_csd(struct mmc_card *card)
 		goto out;
 	}
 
+	ext_csd_struct = ext_csd[EXT_CSD_REV];
+	if (ext_csd_struct > 2) {
+		printk("%s: unrecognised EXT_CSD structure version %d\n",
+			mmc_hostname(card->host), ext_csd_struct);
+		return -EINVAL;
+	}
+
+	if (ext_csd_struct >= 2) {
 		card->ext_csd.sectors =
 			ext_csd[EXT_CSD_SEC_CNT + 0] << 0 |
 			ext_csd[EXT_CSD_SEC_CNT + 1] << 8 |
@@ -216,6 +225,7 @@ static int mmc_read_ext_csd(struct mmc_card *card)
 			ext_csd[EXT_CSD_SEC_CNT + 3] << 24;
 		if (card->ext_csd.sectors)
 			mmc_card_set_blockaddr(card);
+	}
 
 	switch (ext_csd[EXT_CSD_CARD_TYPE]) {
 	case EXT_CSD_CARD_TYPE_52 | EXT_CSD_CARD_TYPE_26:

include/linux/mmc/mmc.h

@@ -227,6 +227,7 @@ struct _mmc_csd {
 #define EXT_CSD_BUS_WIDTH	183	/* R/W */
 #define EXT_CSD_HS_TIMING	185	/* R/W */
 #define EXT_CSD_CARD_TYPE	196	/* RO */
+#define EXT_CSD_REV		192	/* RO */
 #define EXT_CSD_SEC_CNT		212	/* RO, 4 bytes */
 
 /*