linux-kernel - Re: [RFC PATCH for 4.18 1/2] rseq: validate rseq_cs fields are < TASK

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Message-ID: <CA+55aFy2rxnLhbqGtz0wxW_u=x_A1zHZBNP8ZC5P12_AHyb3PA@mail.gmail.com>
Date:   Mon, 2 Jul 2018 12:31:36 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Andy Lutomirski <luto@...capital.net>
Cc:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Andrew Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Dave Watson <davejwatson@...com>, Paul Turner <pjt@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Russell King - ARM Linux <linux@....linux.org.uk>,
        Ingo Molnar <mingo@...hat.com>, Peter Anvin <hpa@...or.com>,
        Andi Kleen <andi@...stfloor.org>,
        Christoph Lameter <cl@...ux.com>, Ben Maurer <bmaurer@...com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Josh Triplett <josh@...htriplett.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Joel Fernandes <joelaf@...gle.com>
Subject: Re: [RFC PATCH for 4.18 1/2] rseq: validate rseq_cs fields are < TASK_SIZE

On Mon, Jul 2, 2018 at 12:02 PM Andy Lutomirski <luto@...capital.net> wrote:
>
> Works for me.  Linus, any objection?

I think the 4.19 stage may be overkill, but I don't hate it, so no
real objections.

If the main reason for this is that we silently clear the upper bits
when returning to compat mode, I actually think that a better fix
would be to just fix that. We shouldn't silently ignore bogus data in
the return path.

But I don't care enough, I think.

            Linus