linux-kernel - Re: [PATCH v5 02/12] array_idx: sanitize speculative array de-references

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Date:   Tue, 30 Jan 2018 11:38:35 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Cyril Novikov <cnovikov@...x.com>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        X86 ML <x86@...nel.org>, Will Deacon <will.deacon@....com>,
        Russell King <linux@...linux.org.uk>,
        Ingo Molnar <mingo@...hat.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        "H. Peter Anvin" <hpa@...or.com>, Alan Cox <alan@...ux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 02/12] array_idx: sanitize speculative array de-references

On Mon, Jan 29, 2018 at 10:29 PM, Dan Williams <dan.j.williams@...el.com> wrote:
>
> Of course, and everything about the technical feedback and suggestions
> was completely valid, on point, and made the patches that much better.
> What wasn't appreciated and what I am tired of grinning and bearing is
> the idea that it's only the maintainer that can show emotion, that
> it's only the maintainer that can be exasperated and burnt out.

Yeah, I think everybody is a bit tired of - and burnt out by - these
patches, and they are subtler and somewhat more core than most are,
which makes the stakes a bit higher too, and the explanations can be a
bit more difficult.

I think everybody is entitled to being a bit snippy occasionally.
Definitely not just maintainers.

So by all means, push right back.

Anyway, I do think the patches I've seen so far are ok, and the real
reason I'm writing this email is actually more about future patches:
do we have a good handle on where these array index sanitations will
be needed?

Also, while array limit checking was obviously the official
"spectre-v1" issue, I do wonder if there are possible other issues
where mispredicted conditional branches can end up leaking
information?

IOW, is there some work on tooling/analysis/similar? Not asking for
near-term, but more of a "big picture" question..

            Linus