[dpdk-dev] [PATCH v7] vhost: fix crash on port deletion

[Gaoxiang Liu <gaoxiangliu0@163.com>]

The rte_vhost_driver_unregister() and vhost_user_read_cb()
can be called at the same time by 2 threads.
when memory of vsocket is freed in rte_vhost_driver_unregister(),
the invalid memory of vsocket is accessed in vhost_user_read_cb().
It's a bug of both mode for vhost as server or client.

E.g., vhostuser port is created as server.
Thread1 calls rte_vhost_driver_unregister().
Before the listen fd is deleted from poll waiting fds,
"vhost-events" thread then calls vhost_user_server_new_connection(),
then a new conn fd is added in fdset when trying to reconnect.
"vhost-events" thread then calls vhost_user_read_cb() and
accesses invalid memory of socket while thread1 frees the memory of
vsocket.

E.g., vhostuser port is created as client.
Thread1 calls rte_vhost_driver_unregister().
Before vsocket of reconn is deleted from reconn list,
"vhost_reconn" thread then calls vhost_user_add_connection()
then a new conn fd is added in fdset when trying to reconnect.
"vhost-events" thread then calls vhost_user_read_cb() and
accesses invalid memory of socket while thread1 frees the memory of
vsocket.

The fix is to move the "fdset_try_del" in front of free memory of conn,
then avoid the race condition.

The core trace is:
Program terminated with signal 11, Segmentation fault.

Fixes: 52d874dc6705 ("vhost: fix crash on closing in client mode")

Signed-off-by: Gaoxiang Liu <liugaoxiang@huawei.com>
---

v2:
* Fix coding style issues.

v3:
* Add detailed log.

v4:
* Add the reason, when vhostuser port is created as server.

v5:
* Add detailed log when vhostuser port is created as client

v6:
* Add 'path' check before deleting listen fd
* Fix spelling issues

v7:
* Fix coding style issues.
---
 lib/vhost/socket.c | 107 ++++++++++++++++++++++-----------------------
 1 file changed, 53 insertions(+), 54 deletions(-)

diff --git a/lib/vhost/socket.c b/lib/vhost/socket.c
index 5d0d728d5..d6f9414c4 100644
--- a/lib/vhost/socket.c
+++ b/lib/vhost/socket.c
@@ -1023,66 +1023,65 @@ rte_vhost_driver_unregister(const char *path)
 
 	for (i = 0; i < vhost_user.vsocket_cnt; i++) {
 		struct vhost_user_socket *vsocket = vhost_user.vsockets[i];
+		if (strcmp(vsocket->path, path))
+			continue;
 
-		if (!strcmp(vsocket->path, path)) {
-			pthread_mutex_lock(&vsocket->conn_mutex);
-			for (conn = TAILQ_FIRST(&vsocket->conn_list);
-			     conn != NULL;
-			     conn = next) {
-				next = TAILQ_NEXT(conn, next);
-
-				/*
-				 * If r/wcb is executing, release vsocket's
-				 * conn_mutex and vhost_user's mutex locks, and
-				 * try again since the r/wcb may use the
-				 * conn_mutex and mutex locks.
-				 */
-				if (fdset_try_del(&vhost_user.fdset,
-						  conn->connfd) == -1) {
-					pthread_mutex_unlock(
-							&vsocket->conn_mutex);
-					pthread_mutex_unlock(&vhost_user.mutex);
-					goto again;
-				}
-
-				VHOST_LOG_CONFIG(INFO,
-					"free connfd = %d for device '%s'\n",
-					conn->connfd, path);
-				close(conn->connfd);
-				vhost_destroy_device(conn->vid);
-				TAILQ_REMOVE(&vsocket->conn_list, conn, next);
-				free(conn);
-			}
-			pthread_mutex_unlock(&vsocket->conn_mutex);
-
-			if (vsocket->is_server) {
-				/*
-				 * If r/wcb is executing, release vhost_user's
-				 * mutex lock, and try again since the r/wcb
-				 * may use the mutex lock.
-				 */
-				if (fdset_try_del(&vhost_user.fdset,
-						vsocket->socket_fd) == -1) {
-					pthread_mutex_unlock(&vhost_user.mutex);
-					goto again;
-				}
-
-				close(vsocket->socket_fd);
-				unlink(path);
-			} else if (vsocket->reconnect) {
-				vhost_user_remove_reconnect(vsocket);
+		if (vsocket->is_server) {
+			/*
+			 * If r/wcb is executing, release vhost_user's
+			 * mutex lock, and try again since the r/wcb
+			 * may use the mutex lock.
+			 */
+			if (fdset_try_del(&vhost_user.fdset, vsocket->socket_fd) == -1) {
+				pthread_mutex_unlock(&vhost_user.mutex);
+				goto again;
 			}
+		} else if (vsocket->reconnect) {
+			vhost_user_remove_reconnect(vsocket);
+		}
 
-			pthread_mutex_destroy(&vsocket->conn_mutex);
-			vhost_user_socket_mem_free(vsocket);
+		pthread_mutex_lock(&vsocket->conn_mutex);
+		for (conn = TAILQ_FIRST(&vsocket->conn_list);
+			 conn != NULL;
+			 conn = next) {
+			next = TAILQ_NEXT(conn, next);
 
-			count = --vhost_user.vsocket_cnt;
-			vhost_user.vsockets[i] = vhost_user.vsockets[count];
-			vhost_user.vsockets[count] = NULL;
-			pthread_mutex_unlock(&vhost_user.mutex);
+			/*
+			 * If r/wcb is executing, release vsocket's
+			 * conn_mutex and vhost_user's mutex locks, and
+			 * try again since the r/wcb may use the
+			 * conn_mutex and mutex locks.
+			 */
+			if (fdset_try_del(&vhost_user.fdset,
+					  conn->connfd) == -1) {
+				pthread_mutex_unlock(&vsocket->conn_mutex);
+				pthread_mutex_unlock(&vhost_user.mutex);
+				goto again;
+			}
 
-			return 0;
+			VHOST_LOG_CONFIG(INFO,
+				"free connfd = %d for device '%s'\n",
+				conn->connfd, path);
+			close(conn->connfd);
+			vhost_destroy_device(conn->vid);
+			TAILQ_REMOVE(&vsocket->conn_list, conn, next);
+			free(conn);
+		}
+		pthread_mutex_unlock(&vsocket->conn_mutex);
+
+		if (vsocket->is_server) {
+			close(vsocket->socket_fd);
+			unlink(path);
 		}
+
+		pthread_mutex_destroy(&vsocket->conn_mutex);
+		vhost_user_socket_mem_free(vsocket);
+
+		count = --vhost_user.vsocket_cnt;
+		vhost_user.vsockets[i] = vhost_user.vsockets[count];
+		vhost_user.vsockets[count] = NULL;
+		pthread_mutex_unlock(&vhost_user.mutex);
+		return 0;
 	}
 	pthread_mutex_unlock(&vhost_user.mutex);
 
-- 
2.32.0