Messages in this thread | | | Date | Fri, 29 May 2020 01:06:59 -0700 | From | Kees Cook <> | Subject | Re: [PATCH v2 1/2] seccomp: notify user trap about unused filter |
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On Fri, May 29, 2020 at 09:56:41AM +0200, Christian Brauner wrote: > On Thu, May 28, 2020 at 04:11:00PM -0700, Kees Cook wrote: > > void seccomp_filter_release(const struct task_struct *tsk) > > { > > struct seccomp_filter *orig = READ_ONCE(tsk->seccomp.filter); > > > > smp_store_release(&tsk->seccomp.filter, NULL); > > I need to go through the memory ordering requirements before I can say > yay or nay confidently to this. :) > > > __seccomp_filter_release(orig); > > }
The only caller will be release_task() after dethread, so honestly this was just me being paranoid. I don't think it actually needs the READ_ONCE() nor the store_release. I think I wrote all that before I'd convinced myself it was safe to remove a filter then. But I'm still suspicious given the various ways release_task() gets called... I just know that if mode 2 is set and filter == NULL, seccomp will fail closed, so I went the paranoid route. :)
-- Kees Cook
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