RDMA/rtrs-srv: Duplicated session name is not allowed

If two clients try to use the same session name, rtrs-server generates a
kernel error that it failed to create the sysfs because the filename
is duplicated.

This patch adds code to check if there already exists the same session
name with the different UUID. If a client tries to add more session,
it sends the UUID and the session name. Therefore it is ok if there is
already same session name with the same UUID. The rtrs-server must fail
only-if there is the same session name with the different UUID.

Link: https://lore.kernel.org/r/20210528113018.52290-17-jinpu.wang@ionos.comSigned-off-by: Gioh Kim <gi-oh.kim@ionos.com>
Signed-off-by: Aleksei Marov <aleksei.marov@ionos.com>
Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Md Haris Iqbal <haris.iqbal@ionos.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/ulp/rtrs/rtrs-srv.c

@@ -753,7 +753,40 @@ static void rtrs_srv_sess_down(struct rtrs_srv_sess *sess)
 	mutex_unlock(&srv->paths_ev_mutex);
 }
 
+static bool exist_sessname(struct rtrs_srv_ctx *ctx,
+			   const char *sessname, const uuid_t *path_uuid)
+{
+	struct rtrs_srv *srv;
+	struct rtrs_srv_sess *sess;
+	bool found = false;
+
+	mutex_lock(&ctx->srv_mutex);
+	list_for_each_entry(srv, &ctx->srv_list, ctx_list) {
+		mutex_lock(&srv->paths_mutex);
+
+		/* when a client with same uuid and same sessname tried to add a path */
+		if (uuid_equal(&srv->paths_uuid, path_uuid)) {
+			mutex_unlock(&srv->paths_mutex);
+			continue;
+		}
+
+		list_for_each_entry(sess, &srv->paths_list, s.entry) {
+			if (strlen(sess->s.sessname) == strlen(sessname) &&
+			    !strcmp(sess->s.sessname, sessname)) {
+				found = true;
+				break;
+			}
+		}
+		mutex_unlock(&srv->paths_mutex);
+		if (found)
+			break;
+	}
+	mutex_unlock(&ctx->srv_mutex);
+	return found;
+}
+
 static int post_recv_sess(struct rtrs_srv_sess *sess);
+static int rtrs_rdma_do_reject(struct rdma_cm_id *cm_id, int errno);
 
 static int process_info_req(struct rtrs_srv_con *con,
 			    struct rtrs_msg_info_req *msg)
@@ -772,10 +805,17 @@ static int process_info_req(struct rtrs_srv_con *con,
 		rtrs_err(s, "post_recv_sess(), err: %d\n", err);
 		return err;
 	}
+
+	if (exist_sessname(sess->srv->ctx,
+			   msg->sessname, &sess->srv->paths_uuid)) {
+		rtrs_err(s, "sessname is duplicated: %s\n", msg->sessname);
+		return -EPERM;
+	}
+	strscpy(sess->s.sessname, msg->sessname, sizeof(sess->s.sessname));
+
 	rwr = kcalloc(sess->mrs_num, sizeof(*rwr), GFP_KERNEL);
 	if (unlikely(!rwr))
 		return -ENOMEM;
-	strscpy(sess->s.sessname, msg->sessname, sizeof(sess->s.sessname));
 
 	tx_sz  = sizeof(*rsp);
 	tx_sz += sizeof(rsp->desc[0]) * sess->mrs_num;