crypto: dh - fix memleak in setkey

commit ee34e264 upstream.

setkey can be called multiple times during the existence
of the transformation object. In case of multiple setkey calls,
the old key was not freed and we leaked memory.
Free the old MPI key if any.
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

crypto/dh.c

@@ -84,6 +84,9 @@ static int dh_set_secret(struct crypto_kpp *tfm, void *buf, unsigned int len)
 	struct dh_ctx *ctx = dh_get_ctx(tfm);
 	struct dh params;
 
+	/* Free the old MPI key if any */
+	dh_free_ctx(ctx);
+
 	if (crypto_dh_decode_key(buf, len, &params) < 0)
 		return -EINVAL;