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Date: Thu, 14 Dec 2017 18:50:32 +0100
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v2 00/17] x86/ldt: Use a VMA based read only mapping
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To: Andy Lutomirski <luto@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>, Linus Torvalds <torvalds@linux-foundation.org>, Dave Hansen <dave.hansen@intel.com>, Borislav Petkov <bpetkov@suse.de>, Greg KH <gregkh@linuxfoundation.org>, Kees Cook <keescook@google.com>, Hugh Dickins <hughd@google.com>, Brian Gerst <brgerst@gmail.com>, Josh Poimboeuf <jpoimboe@redhat.com>, Denys Vlasenko <dvlasenk@redhat.com>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Juergen Gross <jgross@suse.com>, David Laight <David.Laight@aculab.com>, Eduardo Valentin <eduval@amazon.com>, "Liguori, Anthony" <aliguori@amazon.com>, Will Deacon <will.deacon@arm.com>, "linux-mm@kvack.org" <linux-mm@kvack.org>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Dan Williams <dan.j.williams@intel.com>

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.


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