crypto: nx - fix concurrency issue

The NX driver uses the transformation context to store several fields
containing data related to the state of the operations in progress.
Since a single tfm can be used by different kernel threads at the same
time, we need to protect the data stored into the context.

This patch makes use of spin locks to protect the data where a race
condition can happen.

Reviewed-by: Fionnuala Gunter <fin@linux.vnet.ibm.com>
Reviewed-by: Joy Latten <jmlatten@linux.vnet.ibm.com>
Signed-off-by: Marcelo Cerri <mhcerri@linux.vnet.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/nx/nx-aes-gcm.c

@@ -166,8 +166,11 @@ static int gcm_aes_nx_crypt(struct aead_request *req, int enc)
 	struct nx_csbcpb *csbcpb = nx_ctx->csbcpb;
 	struct blkcipher_desc desc;
 	unsigned int nbytes = req->cryptlen;
+	unsigned long irq_flags;
 	int rc = -EINVAL;
 
+	spin_lock_irqsave(&nx_ctx->lock, irq_flags);
+
 	if (nbytes > nx_ctx->ap->databytelen)
 		goto out;
 
@@ -255,6 +258,7 @@ static int gcm_aes_nx_crypt(struct aead_request *req, int enc)
 		     -EBADMSG : 0;
 	}
 out:
+	spin_unlock_irqrestore(&nx_ctx->lock, irq_flags);
 	return rc;
 }