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fork: unify and tighten up CLONE_NEWUSER/CLONE_NEWPID checks

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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>
This commit is contained in:
Oleg Nesterov 2013-09-11 14:19:41 -07:00 committed by Linus Torvalds
parent 5167246a8a
commit 40a0d32d1e
1 changed files with 9 additions and 15 deletions
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24
kernel/fork.c
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@ -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) !=
current->nsproxy->pid_ns_for_children))
return ERR_PTR(-EINVAL);
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