Commit 8382fcac authored Dec 20, 2012 by Eric W. Biederman

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 <oleg@redhat.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

parent a49f0d1e

kernel/fork.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -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;