linux-kernel - Re: [PATCH v2 00/17] x86/ldt: Use a VMA based read only mapping

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Date:   Thu, 14 Dec 2017 18:50:32 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        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 00/17] x86/ldt: Use a VMA based read only mapping

On Thu, Dec 14, 2017 at 08:35:50AM -0800, Andy Lutomirski wrote:

> > @@ -3252,6 +3256,7 @@ static const struct vm_operations_struct
> >         .fault = special_mapping_fault,
> >         .mremap = special_mapping_mremap,
> >         .name = special_mapping_name,
> > +       .split = special_mapping_split,
> >  };
> >
> >  static const struct vm_operations_struct legacy_special_mapping_vmops = {
> 
> Disallowing splitting seems fine.  Disallowing munmap might not be.
> Certainly CRIU relies on being able to mremap() the VDSO.

And for mremap() we need do_munmap() to work, argh.