Commit faf00da5 authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

userns,pidns: Force thread group sharing, not signal handler sharing. 



The code that places signals in signal queues computes the uids, gids,
and pids at the time the signals are enqueued.  Which means that tasks
that share signal queues must be in the same pid and user namespaces.

Sharing signal handlers is fine, but bizarre.

So make the code in fork and userns_install clearer by only testing
for what is functionally necessary.

Also update the comment in unshare about unsharing a user namespace to
be a little more explicit and make a little more sense.

Acked-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
parent 12c641ab

kernel/fork.c

+4 −4
Original line number Original line Diff line number Diff line
@@ -1273,10 +1273,9 @@ static struct task_struct *copy_process(unsigned long clone_flags, 




	/*

	/*

	 * If the new process will be in a different pid or user namespace

	 * If the new process will be in a different pid or user namespace

	 * do not allow it to share a thread group or signal handlers or

	 * do not allow it to share a thread group with the forking task.

	 * parent with the forking task.

	 */

	 */

	if (clone_flags & CLONE_SIGHAND) {

	if (clone_flags & CLONE_THREAD) {

		if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||

		if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||

		    (task_active_pid_ns(current) !=

		    (task_active_pid_ns(current) !=

				current->nsproxy->pid_ns_for_children))

				current->nsproxy->pid_ns_for_children))
@@ -1944,7 +1943,8 @@ SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 
	int err;

	int err;





	/*

	/*

	 * If unsharing a user namespace must also unshare the thread.

	 * If unsharing a user namespace must also unshare the thread group

	 * and unshare the filesystem root and working directories.

	 */

	 */

	if (unshare_flags & CLONE_NEWUSER)

	if (unshare_flags & CLONE_NEWUSER)

		unshare_flags |= CLONE_THREAD | CLONE_FS;

		unshare_flags |= CLONE_THREAD | CLONE_FS;

kernel/user_namespace.c

+2 −2
Original line number Original line Diff line number Diff line
@@ -976,8 +976,8 @@ static int userns_install(struct nsproxy *nsproxy, struct ns_common *ns) 
	if (user_ns == current_user_ns())

	if (user_ns == current_user_ns())

		return -EINVAL;

		return -EINVAL;





	/* Threaded processes may not enter a different user namespace */

	/* Tasks that share a thread group must share a user namespace */

	if (atomic_read(&current->mm->mm_users) > 1)

	if (!thread_group_empty(current))

		return -EINVAL;

		return -EINVAL;





	if (current->fs->users != 1)

	if (current->fs->users != 1)

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