extcap: add check before using pipedata.

In line 1131 the check assumes that pipedata can be NULL. All subsequent
uses require it is not NULL, otherwise it may result in a NULL
dereference.

Found by Clang.

Change-Id: I9bd35b6213adfb41de2e96d5cc6da2b3bac4dd95
Reviewed-on: https://code.wireshark.org/review/30478
Reviewed-by: Pascal Quantin <pascal.quantin@gmail.com>
Petri-Dish: Pascal Quantin <pascal.quantin@gmail.com>
Reviewed-by: Roland Knall <rknall@gmail.com>
Reviewed-by: Anders Broman <a.broman58@gmail.com>

1 files changed, 16 insertions, 14 deletions

diff --git a/extcap.c b/extcap.c
index 7b468be5f8..0132f01172 100644
--- a/extcap.c
+++ b/extcap.c
@@ -1187,23 +1187,25 @@ void extcap_if_cleanup(capture_options *capture_opts, gchar **errormsg)
             interface_opts->extcap_child_watch = 0;
         }
 
-        if (pipedata->stdout_fd > 0)
-        {
-            ws_close(pipedata->stdout_fd);
-        }
+        if (pipedata) {
+            if (pipedata->stdout_fd > 0)
+            {
+                ws_close(pipedata->stdout_fd);
+            }
 
-        if (pipedata->stderr_fd > 0)
-        {
-            ws_close(pipedata->stderr_fd);
-        }
+            if (pipedata->stderr_fd > 0)
+            {
+                ws_close(pipedata->stderr_fd);
+            }
 
-        if (interface_opts->extcap_pid != WS_INVALID_PID)
-        {
-            ws_pipe_close((ws_pipe_t *) interface_opts->extcap_pipedata);
-            interface_opts->extcap_pid = WS_INVALID_PID;
+            if (interface_opts->extcap_pid != WS_INVALID_PID)
+            {
+                ws_pipe_close(pipedata);
+                interface_opts->extcap_pid = WS_INVALID_PID;
 
-            g_free(interface_opts->extcap_pipedata);
-            interface_opts->extcap_pipedata = NULL;
+                g_free(pipedata);
+                interface_opts->extcap_pipedata = NULL;
+            }
         }
     }
 }