linux-kernel - Re: [PATCH 1/3] arm/syscalls: Move address limit check in loop

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Date:   Tue, 25 Jul 2017 13:01:17 -0700
From:   Thomas Garnier <thgarnie@...gle.com>
To:     Russell King - ARM Linux <linux@...linux.org.uk>
Cc:     Leonard Crestez <leonard.crestez@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Dave Martin <Dave.Martin@....com>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Pratyush Anand <panand@...hat.com>,
        linux-arm-kernel@...ts.infradead.org,
        LKML <linux-kernel@...r.kernel.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH 1/3] arm/syscalls: Move address limit check in loop

On Tue, Jul 25, 2017 at 3:38 AM, Russell King - ARM Linux
<linux@...linux.org.uk> wrote:
> On Tue, Jul 25, 2017 at 01:28:01PM +0300, Leonard Crestez wrote:
>> On Mon, 2017-07-24 at 10:07 -0700, Thomas Garnier wrote:
>> > On Wed, Jul 19, 2017 at 10:58 AM, Thomas Garnier <thgarnie@...gle.com
>> > > wrote:
>> > >
>> > > The work pending loop can call set_fs after addr_limit_user_check
>> > > removed the _TIF_FSCHECK flag. To prevent the infinite loop, move
>> > > the addr_limit_user_check call at the beginning of the loop.
>> > >
>> > > Fixes: 73ac5d6a2b6a ("arm/syscalls: Check address limit on user-
>> > > mode return")
>> > > Reported-by: Leonard Crestez <leonard.crestez@....com>
>> > > Signed-off-by: Thomas Garnier <thgarnie@...gle.com>
>>
>> > Any comments on this patch set?
>>
>> Tested-by: Leonard Crestez <leonard.crestez@....com>
>>
>> This appears to fix the original issue of failing to boot from NFS when
>> there are lots of alignment faults. But this is a very basic test
>> relative to the reach of this change.
>>
>> However the original patch has been in linux-next for a while and
>> apparently nobody else noticed system calls randomly hanging on arm.
>>
>> I assume maintainers need to give their opinion.
>
> I've already stated my opinion, which is different from what Linus has
> requested of Thomas.  IMHO, the current approach is going to keep on
> causing problems along the lines that I've already pointed out.

I understand. Do you think this problem apply to arm64 as well?

>
> --
> RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
> FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
> according to speedtest.net.



-- 
Thomas