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Commit 40a0d32d authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

fork: unify and tighten up CLONE_NEWUSER/CLONE_NEWPID checks 



do_fork() denies CLONE_THREAD | CLONE_PARENT if NEWUSER | NEWPID.

Then later copy_process() denies CLONE_SIGHAND if the new process will
be in a different pid namespace (task_active_pid_ns() doesn't match
current->nsproxy->pid_ns).

This looks confusing and inconsistent.  CLONE_NEWPID is very similar to
the case when ->pid_ns was already unshared, we want the same
restrictions so copy_process() should also nack CLONE_PARENT.

And it would be better to deny CLONE_NEWUSER && CLONE_SIGHAND as well
just for consistency.

Kill the "CLONE_NEWUSER | CLONE_NEWPID" check in do_fork() and change
copy_process() to do the same check along with ->pid_ns check we already
have.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarAndy Lutomirski <luto@amacapital.net>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Colin Walters <walters@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5167246a

kernel/fork.c

+9 −15
Original line number Diff line number Diff line
@@ -1173,13 +1173,16 @@ static struct task_struct *copy_process(unsigned long clone_flags, 
		return ERR_PTR(-EINVAL);



	/*

	 * If the new process will be in a different pid namespace don't

	 * allow it to share a thread group or signal handlers with the

	 * forking task.

	 * 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

	 * parent with the forking task.

	 */

	if ((clone_flags & CLONE_SIGHAND) && (task_active_pid_ns(current) !=

	if (clone_flags & (CLONE_SIGHAND | CLONE_PARENT)) {

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

		    (task_active_pid_ns(current) !=

				current->nsproxy->pid_ns_for_children))

			return ERR_PTR(-EINVAL);

	}



	retval = security_task_create(clone_flags);

	if (retval)
@@ -1575,15 +1578,6 @@ long do_fork(unsigned long clone_flags, 
	int trace = 0;

	long nr;



	/*

	 * Do some preliminary argument and permissions checking before we

	 * actually start allocating stuff

	 */

	if (clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) {

		if (clone_flags & (CLONE_THREAD|CLONE_PARENT))

			return -EINVAL;

	}



	/*

	 * Determine whether and which event to report to ptracer.  When

	 * called from kernel_thread or CLONE_UNTRACED is explicitly