wifi: rtl8xxxu: tighten bounds checking in rtl8xxxu_read_efuse()

There some bounds checking to ensure that "map_addr" is not out of
bounds before the start of the loop.  But the checking needs to be
done as we iterate through the loop because "map_addr" gets larger as
we iterate.

Fixes: 26f1fad2 ("New driver: rtl8xxxu (mac80211)")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Jes Sorensen <Jes.Sorensen@gmail.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/Yv8eGLdBslLAk3Ct@kili

drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c

@@ -1878,13 +1878,6 @@ static int rtl8xxxu_read_efuse(struct rtl8xxxu_priv *priv)
 
 		/* We have 8 bits to indicate validity */
 		map_addr = offset * 8;
-		if (map_addr >= EFUSE_MAP_LEN) {
-			dev_warn(dev, "%s: Illegal map_addr (%04x), "
-				 "efuse corrupt!\n",
-				 __func__, map_addr);
-			ret = -EINVAL;
-			goto exit;
-		}
 		for (i = 0; i < EFUSE_MAX_WORD_UNIT; i++) {
 			/* Check word enable condition in the section */
 			if (word_mask & BIT(i)) {
@@ -1895,6 +1888,13 @@ static int rtl8xxxu_read_efuse(struct rtl8xxxu_priv *priv)
 			ret = rtl8xxxu_read_efuse8(priv, efuse_addr++, &val8);
 			if (ret)
 				goto exit;
+			if (map_addr >= EFUSE_MAP_LEN - 1) {
+				dev_warn(dev, "%s: Illegal map_addr (%04x), "
+					 "efuse corrupt!\n",
+					 __func__, map_addr);
+				ret = -EINVAL;
+				goto exit;
+			}
 			priv->efuse_wifi.raw[map_addr++] = val8;
 
 			ret = rtl8xxxu_read_efuse8(priv, efuse_addr++, &val8);