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>

1 files changed, 17 insertions, 7 deletions

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 258fe73eeaa7..cdc38b43b799 100644
--- a/drivers/mmc/core/mmc.c
+++ b/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);
 
@@ -209,13 +210,22 @@ static int mmc_read_ext_csd(struct mmc_card *card)
                 goto out;
         }
 
-        card->ext_csd.sectors =
-                ext_csd[EXT_CSD_SEC_CNT + 0] << 0 |
-                ext_csd[EXT_CSD_SEC_CNT + 1] << 8 |
-                ext_csd[EXT_CSD_SEC_CNT + 2] << 16 |
-                ext_csd[EXT_CSD_SEC_CNT + 3] << 24;
-        if (card->ext_csd.sectors)
-                mmc_card_set_blockaddr(card);
+        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 |
+                        ext_csd[EXT_CSD_SEC_CNT + 2] << 16 |
+                        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: