linux-kernel - Re: [PATCH v2 02/17] mm: Exempt special mappings from mlock(), mprotect() and madvise()

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Message-ID: <20171214173653.s6vsgiwfty3tzyzs@hirez.programming.kicks-ass.net>
Date:   Thu, 14 Dec 2017 18:36:53 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>, X86 ML <x86@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Borislav Petkov <bpetkov@...e.de>,
        Greg KH <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...gle.com>,
        Hugh Dickins <hughd@...gle.com>,
        Brian Gerst <brgerst@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        David Laight <David.Laight@...lab.com>,
        Eduardo Valentin <eduval@...zon.com>,
        "Liguori, Anthony" <aliguori@...zon.com>,
        Will Deacon <will.deacon@....com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH v2 02/17] mm: Exempt special mappings from mlock(),
 mprotect() and madvise()

On Thu, Dec 14, 2017 at 08:19:36AM -0800, Andy Lutomirski wrote:
> On Thu, Dec 14, 2017 at 3:27 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> > It makes no sense to ever prod at special mappings with any of these
> > syscalls.
> >
> > XXX should we include munmap() ?
> 
> This is an ABI break for the vdso.  Maybe that's okay, but mremap() on
> the vdso is certainly used, and I can imagine debuggers using
> mprotect().

*groan*, ok so mremap() will actually still work after this, but yes,
mprotect() will not. I hadn't figured people would muck with the VDSO
like that.