pidns: Outlaw thread creation after unshare(CLONE_NEWPID)

The sequence: unshare(CLONE_NEWPID) clone(CLONE_THREAD|CLONE_SIGHAND|CLONE_VM) Creates a new process in the new pid namespace without setting pid_ns->child_reaper. After forking this results in a NULL pointer dereference. Avoid this and other nonsense scenarios that can show up after creating a new pid namespace with unshare by adding a new check in copy_prodcess. Pointed-out-by: Oleg Nesterov <[email protected]> Acked-by: Oleg Nesterov <[email protected]> Signed-off-by: "Eric W. Biederman" <[email protected]>
chewitt · Dec 25, 2012 · 8382fca · 8382fca
1 parent a49f0d1
commit 8382fca
Showing 1 changed file with 8 additions and 0 deletions.
diff --git a/kernel/fork.c b/kernel/fork.c
@@ -1166,6 +1166,14 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 				current->signal->flags & SIGNAL_UNKILLABLE)
 		return ERR_PTR(-EINVAL);
 
+	/*
+	 * If the new process will be in a different pid namespace
+	 * don't allow the creation of threads.
+	 */
+	if ((clone_flags & (CLONE_VM|CLONE_NEWPID)) &&
+	    (task_active_pid_ns(current) != current->nsproxy->pid_ns))
+		return ERR_PTR(-EINVAL);
+
 	retval = security_task_create(clone_flags);
 	if (retval)
 		goto fork_out;