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

From: Catalin Marinas <catalin.marinas-5wv7dgnIgG8@public.gmane.org>
To: Thomas Garnier <thgarnie-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Cc: Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>,
	Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	"H . Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>,
	Andy Lutomirski <luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	Paolo Bonzini <pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Rik van Riel <riel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Josh Poimboeuf <jpoimboe-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Petr Mladek <pmladek-IBi9RG/b67k@public.gmane.org>,
	Miroslav Benes <mbenes-AlSwsSmVLrQ@public.gmane.org>,
	Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
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	Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>,
	Dave Hansen <dave.hansen-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
	David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Russell King <linux-I+IVW8TIWO2tmTQ+vhA3Yw@public.gmane.org>,
	Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>,
	Will Drewry <wad-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
	Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>,
	Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>,
	Pratyush Anand <panand-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Subject: Re: [PATCH v10 3/3] arm64/syscalls: Check address limit on user-mode return
Date: Wed, 21 Jun 2017 09:16:01 +0100	[thread overview]
Message-ID: <20170621081601.g6fsf6i3mxzar5sn@localhost> (raw)
In-Reply-To: <20170615011203.144108-3-thgarnie-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>

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-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
> ---
> 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-5wv7dgnIgG8@public.gmane.org>