linux-kernel - Re: [PATCH v8 1/4] syscalls: Verify address limit before returning to user-mode

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Message-ID: <20170428063323.ntnc4tk7do2dor76@gmail.com>
Date:   Fri, 28 Apr 2017 08:33:23 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Thomas Garnier <thgarnie@...gle.com>
Cc:     Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Arnd Bergmann <arnd@...db.de>,
        David Howells <dhowells@...hat.com>,
        René Nyffenegger <mail@...enyffenegger.ch>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Oleg Nesterov <oleg@...hat.com>,
        Pavel Tikhomirov <ptikhomirov@...tuozzo.com>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Rik van Riel <riel@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Russell King <linux@...linux.org.uk>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>,
        linux-s390 <linux-s390@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH v8 1/4] syscalls: Verify address limit before returning
 to user-mode


* Thomas Garnier <thgarnie@...gle.com> wrote:

> > BTW., a further simplification would be:
> >
> > #ifndef ADDR_LIMIT_CHECK_PRE
> > # define ADDR_LIMIT_CHECK_PRE ...
> > #endif
> >
> > This way architectures could override this generic functionality simply by
> > defining the helpers. Architectures that don't do that get the generic version.
> 
> I don't think architectures need to do that. The optimizations are
> embedding the checks on their architecture-specific code to make it
> faster and remove the size impact. The pre/post is fine for the rest.

Indeed, only the generic code needs to turn off that code - architectures will 
place these callbacks elsewhere.

Thanks,

	Ingo