spi_mpc83xx: reject invalid transfer sizes

Error out on transfer length != multiple of bytes per word with -EINVAL.
Fixes a buffer overrun crash if length < bytes per word.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Acked-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/spi/spi_mpc83xx.c

@@ -312,11 +312,20 @@ static int mpc83xx_spi_bufs(struct spi_device *spi, struct spi_transfer *t)
 	if (t->bits_per_word)
 		bits_per_word = t->bits_per_word;
 	len = t->len;
-	if (bits_per_word > 8)
+	if (bits_per_word > 8) {
+		/* invalid length? */
+		if (len & 1)
+			return -EINVAL;
 		len /= 2;
-	if (bits_per_word > 16)
+	}
+	if (bits_per_word > 16) {
+		/* invalid length? */
+		if (len & 1)
+			return -EINVAL;
 		len /= 2;
+	}
 	mpc83xx_spi->count = len;
+
 	INIT_COMPLETION(mpc83xx_spi->done);
 
 	/* enable rx ints */