Fix: lttng: initialize sessions pointer to NULL

lttng_list_sessions does not set the passed pointer to NULL on empty
return. This leads to a deallocation of an invalid pointer (segfault).

For returns of size 0, the value of the passed argument should be
considered "undefined".

Refactor error handling a bit by removing the "error" jump. Always
call free on the 'sessions' object.

Fixes #1205

Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/src/bin/lttng/commands/list.c b/src/bin/lttng/commands/list.c
index 28166c8be28e5a9588d14d8f14adfd56a39810dd..65d8ea6f5c45424444262f87dd4ff7c7e38bbb70 100644 (file)
--- a/src/bin/lttng/commands/list.c
+++ b/src/bin/lttng/commands/list.c
@@ -1825,7 +1825,7 @@ static int list_sessions(const char *session_name)
        int ret = CMD_SUCCESS;
        int count, i;
        unsigned int session_found = 0;
-       struct lttng_session *sessions;
+       struct lttng_session *sessions = NULL;
 
        count = lttng_list_sessions(&sessions);
        DBG("Session count %d", count);
@@ -1838,7 +1838,7 @@ static int list_sessions(const char *session_name)
        if (lttng_opt_mi) {
                /* Mi */
                if (session_name == NULL) {
-                       /* List all session */
+                       /* List all sessions */
                        ret = mi_list_sessions(sessions, count);
                } else {
                        /* Note : this return an open session element */
@@ -1846,7 +1846,7 @@ static int list_sessions(const char *session_name)
                }
                if (ret) {
                        ret = CMD_ERROR;
-                       goto error;
+                       goto end;
                }
        } else {
                /* Pretty print */
@@ -1893,7 +1893,7 @@ static int list_sessions(const char *session_name)
                if (!session_found && session_name != NULL) {
                        ERR("Session '%s' not found", session_name);
                        ret = CMD_ERROR;
-                       goto error;
+                       goto end;
                }
 
                if (session_name == NULL) {
@@ -1901,9 +1901,8 @@ static int list_sessions(const char *session_name)
                }
        }
 
-error:
-       free(sessions);
 end:
+       free(sessions);
        return ret;
 }