linux-kernel - Re: [PATCH] x86/uaccess: Use pointer masking to limit uaccess speculation

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Message-ID: <20200901145442.GC95447@C02TD0UTHF1T.local>
Date:   Tue, 1 Sep 2020 15:54:42 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Christoph Hellwig <hch@....de>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Will Deacon <will@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Waiman Long <longman@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH] x86/uaccess: Use pointer masking to limit uaccess
 speculation

On Tue, Sep 01, 2020 at 04:46:41PM +0200, Christoph Hellwig wrote:
> On Tue, Sep 01, 2020 at 03:02:08PM +0100, Mark Rutland wrote:
> > One thing to consider is whether you need a speculation barrier after
> > set_fs(). Otherwise for code like:
> 
> FYI, at least for x86 and powerpc I have a pending series to kill
> set_fs().  I'd love to see someone help with the arm/arm64 side, otherwise
> I'll try to get to it eventually.

Is there anything in particular that's tricky, or do you just want
someone to look generally? From a quick grep arch/arm64/* looks clean, but
I suspect that's misleading.

Thanks,
Mark.