Re: [PATCH] seccomp: add ptrace commands for suspend/resume

quoted

+int suspend_seccomp(struct task_struct *task)
+{
+	int ret = -EACCES;
+
+	spin_lock_irq(&task->sighand->siglock);
+
+	if (!capable(CAP_SYS_ADMIN))
+		goto out;

I am puzzled ;) Why do we need ->siglock? And even if we need it, why
we can't check CAP_SYS_ADMIN lockless?

And I am not sure I understand why do we need the additional security
check, but I leave this to you and Andy.

If you have the rights to trace this task, then you can do anything
the tracee could do without the filtering.

I think _this_ check is required, otherwise the seccomp-ed task (in
filtered mode) fork-s a child, then this child ptrace-attach to parent
(allowed) then suspend its seccomd. And -- we have unpriviledged process 
de-seccomped.

-- Pavel