[dpdk-dev] [PATCH v4] vhost: fix crash on port deletion

[Gaoxiang Liu <gaoxiangliu0@163.com>]

The rte_vhost_driver_unregister() and vhost_user_server_new_connection()
can be called at the same time by 2 threads.
Eg thread1 calls rte_vhost_driver_unregister() and frees the memory of
conn_list.
"vhost-events" thread calls fdset_event_dispatch,
then calls vhost_user_server_new_connection().
A new conn fd is added in fdset in vhost_user_server_new_connection(),
then "vhost-events" thread calls vhost_user_read_cb().
when thread1 frees the memory of vsocket, vhost_user_read_cb()
will access invalid memory of socket.

When vhostuser port is created as a client, the issue also exists.

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 a server.
---
 lib/vhost/socket.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/lib/vhost/socket.c b/lib/vhost/socket.c
index 5d0d728d5..2eb8fcadd 100644
--- a/lib/vhost/socket.c
+++ b/lib/vhost/socket.c
@@ -1024,6 +1024,20 @@ 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 (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);
+		}
+
 		if (!strcmp(vsocket->path, path)) {
 			pthread_mutex_lock(&vsocket->conn_mutex);
 			for (conn = TAILQ_FIRST(&vsocket->conn_list);
@@ -1056,21 +1070,8 @@ rte_vhost_driver_unregister(const char *path)
 			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);
 			}
 
 			pthread_mutex_destroy(&vsocket->conn_mutex);
-- 
2.32.0