Do not dereference 'siw_crypto_shash' before checking

Reported-by: "Dan Carpenter" <dan.carpenter@oracle.com>
Fixes: f29dd55b02 ("rdma/siw: queue pair methods")
Link: https://lore.kernel.org/r/OF61E386ED.49A73798-ON00258444.003BD6A6-00258444.003CC8D9@notes.na.collabserv.com
Signed-off-by: Bernard Metzler <bmt@zurich.ibm.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/sw/siw/siw_qp.c

@@ -220,12 +220,14 @@ static int siw_qp_enable_crc(struct siw_qp *qp)
 {
 	struct siw_rx_stream *c_rx = &qp->rx_stream;
 	struct siw_iwarp_tx *c_tx = &qp->tx_ctx;
-	int size = crypto_shash_descsize(siw_crypto_shash) +
-			sizeof(struct shash_desc);
+	int size;
 
 	if (siw_crypto_shash == NULL)
 		return -ENOENT;
 
+	size = crypto_shash_descsize(siw_crypto_shash) +
+		sizeof(struct shash_desc);
+
 	c_tx->mpa_crc_hd = kzalloc(size, GFP_KERNEL);
 	c_rx->mpa_crc_hd = kzalloc(size, GFP_KERNEL);
 	if (!c_tx->mpa_crc_hd || !c_rx->mpa_crc_hd) {