On Fri, Oct 24, 2025 at 12:52:40PM +0200, Christian Brauner wrote:

...

...

+void get_cred_namespaces(struct task_struct *tsk)
+{
+	ns_ref_active_get(tsk->real_cred->user_ns);

Hi Christian,

real_cred is protected by RCU, but this code doesn't seem to take
that into account. Or, at least Sparse doesn't think so:

.../nsproxy.c:264:9: error: no generic selection for 'struct user_namespace *const [noderef] __rcu user_ns'
.../nsproxy.c:264:9: warning: dereference of noderef expression

+}
+
+void exit_cred_namespaces(struct task_struct *tsk)
+{
+	ns_ref_active_put(tsk->real_cred->user_ns);

Likewise here.

+}
+
 int exec_task_namespaces(void)
 {
 	struct task_struct *tsk = current;

...