linux-kernel - Re: [PATCH 4/4] arm64/syscalls: Move address limit check in loop

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Date:   Tue, 12 Sep 2017 11:28:50 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Will Deacon <will.deacon@....com>, Ingo Molnar <mingo@...nel.org>
Cc:     Thomas Garnier <thgarnie@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Andy Lutomirski <luto@...capital.net>,
        Will Drewry <wad@...omium.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Dave Martin <Dave.Martin@....com>,
        Pratyush Anand <panand@...hat.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Arnd Bergmann <arnd@...db.de>,
        David Howells <dhowells@...hat.com>,
        Yonghong Song <yhs@...com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Linux API <linux-api@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] arm64/syscalls: Move address limit check in loop

On Tue, Sep 12, 2017 at 11:27 AM, Will Deacon <will.deacon@....com> wrote:
> Hi Kees,
>
> On Thu, Sep 07, 2017 at 08:30:47AM -0700, Kees Cook wrote:
>> From: Thomas Garnier <thgarnie@...gle.com>
>>
>> A bug was reported on ARM where set_fs might be called after it was
>> checked on the work pending function. ARM64 is not affected by this bug
>> but has a similar construct. In order to avoid any similar problems in
>> the future, the addr_limit_user_check function is moved at the beginning
>> of the loop.
>>
>> Fixes: cf7de27ab351 ("arm64/syscalls: Check address limit on user-mode return")
>> Reported-by: Leonard Crestez <leonard.crestez@....com>
>> Signed-off-by: Thomas Garnier <thgarnie@...gle.com>
>> Signed-off-by: Kees Cook <keescook@...omium.org>
>> ---
>>  arch/arm64/kernel/signal.c | 6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> What's the plan for this series? It looks like somehow an old v2 of the
> original series made it into mainline, so I'd like to see these fixes get
> in ASAP. I'm still slightly nervous about pathological setting of the
> FSCHECK flag due to e.g. a PMU IRQ causing a livelock in do_notify_resume,
> but that's at least less likely with this fix :/

Hi! I resent this to Ingo to pick up for -tip. I think he's waiting
for -rc1, IIUC. Ingo, can you comment on timing for this getting sent
to Linus?

-Kees

-- 
Kees Cook
Pixel Security