join: add fexecve fallback for shells

Allows users to join a sandbox and get a shell even
if there is none in the sandbox mount namespace.
There are few limitations:
1. This will fail with scripted shells (see man 3 fexecve for an explanation)
2. Shell process names are not user friendly

1 files changed, 2 insertions, 2 deletions

diff --git a/src/firejail/no_sandbox.c b/src/firejail/no_sandbox.c
index 01df77ee6..22f36ef07 100644
--- a/src/firejail/no_sandbox.c
+++ b/src/firejail/no_sandbox.c
@@ -211,7 +211,7 @@ void run_no_sandbox(int argc, char **argv) {
         }
 
         if (prog_index == 0) {
-                cfg.command_line = cfg.shell;
+                assert(cfg.command_line == NULL); // runs cfg.shell
                 cfg.window_title = cfg.shell;
         } else {
                 build_cmdline(&cfg.command_line, &cfg.window_title, argc, argv, prog_index);
@@ -230,5 +230,5 @@ void run_no_sandbox(int argc, char **argv) {
 
         arg_quiet = 1;
 
-        start_application(1, NULL);
+        start_application(1, -1, NULL);
 }