fork: unify and tighten up CLONE_NEWUSER/CLONE_NEWPID checks (40a0d32d) · Commits · 戴 / test

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:

Oleg Nesterov <oleg@redhat.com> Acked-by:

Andy Lutomirski <luto@amacapital.net> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Colin Walters <walters@redhat.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

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

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