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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Mon, 2 Jul 2018 12:31:36 -0700
Message-ID: <CA+55aFy2rxnLhbqGtz0wxW_u=x_A1zHZBNP8ZC5P12_AHyb3PA@mail.gmail.com>
Subject: Re: [RFC PATCH for 4.18 1/2] rseq: validate rseq_cs fields are < TASK_SIZE
To:     Andy Lutomirski <luto@amacapital.net>
Cc:     Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Andrew Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux API <linux-api@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        Dave Watson <davejwatson@fb.com>, Paul Turner <pjt@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Russell King - ARM Linux <linux@arm.linux.org.uk>,
        Ingo Molnar <mingo@redhat.com>, Peter Anvin <hpa@zytor.com>,
        Andi Kleen <andi@firstfloor.org>,
        Christoph Lameter <cl@linux.com>, Ben Maurer <bmaurer@fb.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Josh Triplett <josh@joshtriplett.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Michael Kerrisk <mtk.manpages@gmail.com>,
        Joel Fernandes <joelaf@google.com>
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On Mon, Jul 2, 2018 at 12:02 PM Andy Lutomirski <luto@amacapital.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