linux-kernel - Re: [PATCH 2/2] mm: soft_dirty: userfaultfd: introduce wrprotect_tlb_flush

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <b5024da1-c1ee-263c-cd32-814846a8d7f0@nvidia.com>
Date:   Thu, 7 Jan 2021 14:37:35 -0800
From:   John Hubbard <jhubbard@...dia.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
CC:     Andrea Arcangeli <aarcange@...hat.com>,
        Linux-MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Yu Zhao <yuzhao@...gle.com>, Andy Lutomirski <luto@...nel.org>,
        Peter Xu <peterx@...hat.com>,
        Pavel Emelyanov <xemul@...nvz.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        "Minchan Kim" <minchan@...nel.org>, Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Hugh Dickins <hughd@...gle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Oleg Nesterov <oleg@...hat.com>, Jann Horn <jannh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Leon Romanovsky <leonro@...dia.com>,
        Jason Gunthorpe <jgg@...pe.ca>, Jan Kara <jack@...e.cz>,
        Kirill Tkhai <ktkhai@...tuozzo.com>
Subject: Re: [PATCH 2/2] mm: soft_dirty: userfaultfd: introduce
 wrprotect_tlb_flush_pending

On 1/7/21 2:24 PM, Linus Torvalds wrote:
> On Thu, Jan 7, 2021 at 2:20 PM Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
>>
>> Hmm, add a check for the page being PageAnon(), perhaps?
>>
>> If it's a shared vma, then the page can be pinned shared with multiple
>> mappings, I agree.
> 
> Or check the vma directly for whether it's a COW vma. That's probably
> a more obvious test, but would have to be done outside of
> page_maybe_dma_pinned().
> 
> For example, in copy_present_page(), we've already done that COW-vma
> test, so if we want to strengthen just _that_ test, then it would be
> sufficient to just add a
> 
>          /* This cannot be a pinned page if it has more than one mapping */
>          if (page_mappings(page) != 1)
>                  return 1;
> 
> to copy_present_page() along with the existing page_maybe_dma_pinned() test.
> 
> No?
> 
>              Linus

That approach makes me a lot happier, yes. Because it doesn't add constraints
to the RDMA cases, but still does what we need here.


thanks,
-- 
John Hubbard
NVIDIA