fix: ust comm error handling segfault

On comm errors, UST should not try to populate fields from NULL
pointers.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/liblttng-ust/lttng-ust-comm.c b/liblttng-ust/lttng-ust-comm.c
index 86cce18d57fe658588db907ed8016f39e95f975f..36f57efb25f4d97c31bcb04b7fd207f2807b9a8c 100644 (file)
--- a/liblttng-ust/lttng-ust-comm.c
+++ b/liblttng-ust/lttng-ust-comm.c
@@ -284,28 +284,30 @@ end:
                //lur.ret_code = USTCOMM_SESSION_FAIL;
                lur.ret_code = ret;
        }
-       switch (lum->cmd) {
-       case LTTNG_UST_STREAM:
-               /*
-                * Special-case reply to send stream info.
-                * Use lum.u output.
-                */
-               lur.u.stream.memory_map_size = *args.stream.memory_map_size;
-               shm_fd = *args.stream.shm_fd;
-               wait_fd = *args.stream.wait_fd;
-               break;
-       case LTTNG_UST_METADATA:
-       case LTTNG_UST_CHANNEL:
-               lur.u.channel.memory_map_size = *args.channel.memory_map_size;
-               shm_fd = *args.channel.shm_fd;
-               wait_fd = *args.channel.wait_fd;
-               break;
-       case LTTNG_UST_TRACER_VERSION:
-               lur.u.version = lum->u.version;
-               break;
-       case LTTNG_UST_TRACEPOINT_LIST_GET:
-               memcpy(&lur.u.tracepoint, &lum->u.tracepoint, sizeof(lur.u.tracepoint));
-               break;
+       if (ret >= 0) {
+               switch (lum->cmd) {
+               case LTTNG_UST_STREAM:
+                       /*
+                        * Special-case reply to send stream info.
+                        * Use lum.u output.
+                        */
+                       lur.u.stream.memory_map_size = *args.stream.memory_map_size;
+                       shm_fd = *args.stream.shm_fd;
+                       wait_fd = *args.stream.wait_fd;
+                       break;
+               case LTTNG_UST_METADATA:
+               case LTTNG_UST_CHANNEL:
+                       lur.u.channel.memory_map_size = *args.channel.memory_map_size;
+                       shm_fd = *args.channel.shm_fd;
+                       wait_fd = *args.channel.wait_fd;
+                       break;
+               case LTTNG_UST_TRACER_VERSION:
+                       lur.u.version = lum->u.version;
+                       break;
+               case LTTNG_UST_TRACEPOINT_LIST_GET:
+                       memcpy(&lur.u.tracepoint, &lum->u.tracepoint, sizeof(lur.u.tracepoint));
+                       break;
+               }
        }
        ret = send_reply(sock, &lur);
        if (ret < 0) {