Fix double-free in crun exec

The process struct cleanup in crun_command_exec was doubly freeing the
process->user pointer, which was previously freed by the container struct
cleanup in libcrun_container_exec_with_options.

src/libcrun/container.c

@@ -537,6 +537,30 @@ make_container (runtime_spec_schema_config_schema *container_def, const char *pa
   return container;
 }
 
+runtime_spec_schema_config_schema_process_user *
+process_user_dup (const runtime_spec_schema_config_schema_process_user *const src)
+{
+  runtime_spec_schema_config_schema_process_user *const dst = xmalloc0 (sizeof (runtime_spec_schema_config_schema_process_user));
+
+  dst->uid = src->uid;
+  dst->uid_present = src->uid_present;
+  dst->gid = src->gid;
+  dst->gid_present = src->gid_present;
+  dst->umask = src->umask;
+  dst->umask_present = src->umask_present;
+
+  if (src->additional_gids)
+    {
+      const size_t additional_gids_size = src->additional_gids_len * sizeof (gid_t);
+      dst->additional_gids = xmalloc (additional_gids_size);
+      memcpy (dst->additional_gids, src->additional_gids, additional_gids_size);
+    }
+
+  dst->username = xstrdup (src->username);
+
+  return dst;
+}
+
 libcrun_container_t *
 libcrun_container_load_from_memory (const char *json, libcrun_error_t *err)
 {
@@ -3620,7 +3644,7 @@ libcrun_container_exec_with_options (libcrun_context_t *context, const char *id,
         process->apparmor_profile = xstrdup (container->container_def->process->apparmor_profile);
 
       if (process->user == NULL && container->container_def->process->user)
-        process->user = container->container_def->process->user;
+        process->user = process_user_dup (container->container_def->process->user);
     }
 
   ret = initialize_security (process, err);