Messages in this thread | | | Date | Tue, 24 Jun 2014 19:08:00 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH v7 7/9] seccomp: implement SECCOMP_FILTER_FLAG_TSYNC |
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On 06/23, Kees Cook wrote: > > +static pid_t seccomp_can_sync_threads(void) > +{ > + struct task_struct *thread, *caller; > + > + BUG_ON(write_can_lock(&tasklist_lock)); > + BUG_ON(!spin_is_locked(¤t->sighand->siglock)); > + > + if (current->seccomp.mode != SECCOMP_MODE_FILTER) > + return -EACCES; > + > + /* Validate all threads being eligible for synchronization. */ > + thread = caller = current; > + for_each_thread(caller, thread) {
You only need to initialize "caller" for for_each_thread(). Same for seccomp_sync_threads().
> @@ -586,6 +701,17 @@ static long seccomp_set_mode_filter(unsigned int flags, > if (IS_ERR(prepared)) > return PTR_ERR(prepared); > > + /* > + * If we're doing thread sync, we must hold tasklist_lock > + * to make sure seccomp filter changes are stable on threads > + * entering or leaving the task list. And we must take it > + * before the sighand lock to avoid deadlocking. > + */ > + if (flags & SECCOMP_FILTER_FLAG_TSYNC) > + write_lock_irqsave(&tasklist_lock, taskflags); > + else > + __acquire(&tasklist_lock); /* keep sparse happy */ > +
Why? ->siglock should be enough, it seems.
It obviously does not protect the global process list, but *sync_threads() only care about current's thread group list, no?
Oleg.
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