Hello.
Colin reports that vfork() doesn't work after unshare(PIDNS). The
reason is trivial, copy_process() does:
/*
* If the new process will be in a different pid namespace
* don't allow the creation of threads.
*/
if ((clone_flags & (CLONE_VM|CLONE_NEWPID)) &&
(task_active_pid_ns(current) != current->nsproxy->pid_ns))
return ERR_PTR(-EINVAL);
and CLONE_VM obviously nacks vfork(). So perhaps we can relax
this check to CLONE_THREAD? Or should we really nack CLONE_VM
by security reasons?
OTOH. Perhaps we should also deny CLONE_PARENT in this case?
In short. So far I am thinking about the patch below but I got
lost and totally confused. Will try to think more tomorrow, but
I would like to see the fix from someone who still understands
this all.
Oleg.
--- x/kernel/fork.c 2013-08-14 18:34:06.000000000 +0200
+++ x/kernel/fork.c 2013-08-19 19:03:43.848823039 +0200
@@ -1172,14 +1172,6 @@ static struct task_struct *copy_process(
current->signal->flags & SIGNAL_UNKILLABLE)
return ERR_PTR(-EINVAL);
- /*
- * If the new process will be in a different pid namespace
- * don't allow the creation of threads.
- */
- if ((clone_flags & (CLONE_VM|CLONE_NEWPID)) &&
- (task_active_pid_ns(current) != current->nsproxy->pid_ns))
- return ERR_PTR(-EINVAL);
-
retval = security_task_create(clone_flags);
if (retval)
goto fork_out;
@@ -1578,8 +1570,9 @@ long do_fork(unsigned long clone_flags,
* 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))
+ if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
+ (task_active_pid_ns(current) != current->nsproxy->pid_ns)) {
+ if (clone_flags & (CLONE_THREAD | CLONE_PARENT | CLONE_NEWPID))
return -EINVAL;
}
--
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