linux-kernel - Re: [RFC][PATCH 7/7] kref: Implement using refcount

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Date:   Tue, 15 Nov 2016 10:06:28 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Will Deacon <will.deacon@....com>,
        "Reshetova, Elena" <elena.reshetova@...el.com>,
        Arnd Bergmann <arnd@...db.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        David Windsor <dave@...gbits.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH 7/7] kref: Implement using refcount_t

On Tue, Nov 15, 2016 at 5:03 AM, Ingo Molnar <mingo@...nel.org> wrote:
>
> * Peter Zijlstra <peterz@...radead.org> wrote:
>
>> On Tue, Nov 15, 2016 at 11:03:59AM +0100, Ingo Molnar wrote:
>> > > Should I also make a CONFIG knob that implements refcount_t with the
>> > > 'normal' atomic_t primitives?
>> >
>> > I'd suggest doing the saturation/safe-wrap semantics only for now (i.e. the
>> > current patch, split into two perhaps), and reconsider if there's any complaints?
>> >
>> > > And possibly another knob to toggle the BUG()s into WARN()s. With the
>> > > full saturation semantics WARN() is a lot safer and will not corrupt
>> > > kernel state as much.

I'll want to modify this in the future; I have a config already doing
"Bug on data structure corruption" that makes the warn/bug choice.
It'll need some massaging to fit into the new refcount_t checks, but
it should be okay -- there needs to be a way to complete the
saturation, etc, but still kill the offending process group.

-Kees

-- 
Kees Cook
Nexus Security