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 09:16:01 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Thomas Garnier <thgarnie@...gle.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@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH v10 3/3] arm64/syscalls: Check address limit on user-mode
 return

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>