linux-kernel - Re: [PATCH v10 3/3] arm64/syscalls: Check address limit on user-mode return

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Date:   Wed, 21 Jun 2017 06:57:44 -0700
From:   Thomas Garnier <thgarnie@...gle.com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Rik van Riel <riel@...hat.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Petr Mladek <pmladek@...e.com>,
        Miroslav Benes <mbenes@...e.cz>,
        Kees Cook <keescook@...omium.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Arnd Bergmann <arnd@...db.de>,
        Dave Hansen <dave.hansen@...el.com>,
        David Howells <dhowells@...hat.com>,
        Russell King <linux@...linux.org.uk>,
        Andy Lutomirski <luto@...capital.net>,
        Will Drewry <wad@...omium.org>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Pratyush Anand <panand@...hat.com>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Linux API <linux-api@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH v10 3/3] arm64/syscalls: Check address limit on user-mode return

On Wed, Jun 21, 2017 at 1:16 AM, Catalin Marinas
<catalin.marinas@....com> wrote:
> On Wed, Jun 14, 2017 at 06:12:03PM -0700, Thomas Garnier wrote:
>> Ensure the address limit is a user-mode segment before returning to
>> user-mode. Otherwise a process can corrupt kernel-mode memory and
>> elevate privileges [1].
>>
>> The set_fs function sets the TIF_SETFS flag to force a slow path on
>> return. In the slow path, the address limit is checked to be USER_DS if
>> needed.
>>
>> [1] https://bugs.chromium.org/p/project-zero/issues/detail?id=990
>>
>> Signed-off-by: Thomas Garnier <thgarnie@...gle.com>
>> ---
>> v10 redesigns the change to use work flags on set_fs as recommended by
>> Linus and agreed by others.
>>
>> Based on next-20170609
>> ---
>>  arch/arm64/include/asm/thread_info.h | 4 +++-
>>  arch/arm64/include/asm/uaccess.h     | 3 +++
>>  arch/arm64/kernel/signal.c           | 5 +++++
>>  3 files changed, 11 insertions(+), 1 deletion(-)
>
> For arm64:
>
> Reviewed-by: Catalin Marinas <catalin.marinas@....com>

Thanks Catalin

-- 
Thomas