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: 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>
diff --git a/kernel/fork.c b/kernel/fork.c
index 68d508f..84703db 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1173,13 +1173,16 @@
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)
@@ -1576,15 +1579,6 @@
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
* requested, no event is reported; otherwise, report if the event
