cifs: Allocate encryption header through kmalloc

When encryption is used, smb2_transform_hdr is defined on the stack and is
passed to the transport. This doesn't work with RDMA as the buffer needs to
be DMA'ed.

Fix it by using kmalloc.
Signed-off-by: Long Li <longli@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/transport.c

@@ -466,7 +466,7 @@ smb_send_rqst(struct TCP_Server_Info *server, int num_rqst,
 	      struct smb_rqst *rqst, int flags)
 {
 	struct kvec iov;
-	struct smb2_transform_hdr tr_hdr;
+	struct smb2_transform_hdr *tr_hdr;
 	struct smb_rqst cur_rqst[MAX_COMPOUND];
 	int rc;
 
@@ -476,28 +476,34 @@ smb_send_rqst(struct TCP_Server_Info *server, int num_rqst,
 	if (num_rqst > MAX_COMPOUND - 1)
 		return -ENOMEM;
 
-	memset(&cur_rqst[0], 0, sizeof(cur_rqst));
-	memset(&iov, 0, sizeof(iov));
-	memset(&tr_hdr, 0, sizeof(tr_hdr));
-
-	iov.iov_base = &tr_hdr;
-	iov.iov_len = sizeof(tr_hdr);
-	cur_rqst[0].rq_iov = &iov;
-	cur_rqst[0].rq_nvec = 1;
-
 	if (!server->ops->init_transform_rq) {
 		cifs_server_dbg(VFS, "Encryption requested but transform "
 				"callback is missing\n");
 		return -EIO;
 	}
 
+	tr_hdr = kmalloc(sizeof(*tr_hdr), GFP_NOFS);
+	if (!tr_hdr)
+		return -ENOMEM;
+
+	memset(&cur_rqst[0], 0, sizeof(cur_rqst));
+	memset(&iov, 0, sizeof(iov));
+	memset(tr_hdr, 0, sizeof(*tr_hdr));
+
+	iov.iov_base = tr_hdr;
+	iov.iov_len = sizeof(*tr_hdr);
+	cur_rqst[0].rq_iov = &iov;
+	cur_rqst[0].rq_nvec = 1;
+
 	rc = server->ops->init_transform_rq(server, num_rqst + 1,
 					    &cur_rqst[0], rqst);
 	if (rc)
-		return rc;
+		goto out;
 
 	rc = __smb_send_rqst(server, num_rqst + 1, &cur_rqst[0]);
 	smb3_free_compound_rqst(num_rqst, &cur_rqst[1]);
+out:
+	kfree(tr_hdr);
 	return rc;
 }