linux-kernel - Re: mmap denywrite mess (Was: [GIT PULL] overlayfs fixes for 5.14-rc6)

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Message-ID: <a540ba9f-6d3b-4d49-0424-b100bcdf38bf@redhat.com>
Date:   Thu, 12 Aug 2021 09:12:53 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Miklos Szeredi <miklos@...redi.hu>,
        Christian König <christian.koenig@....com>,
        Matthew Wilcox <willy@...radead.org>,
        linux-mm <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-unionfs@...r.kernel.org
Subject: Re: mmap denywrite mess (Was: [GIT PULL] overlayfs fixes for
 5.14-rc6)

On 11.08.21 18:20, Linus Torvalds wrote:
> On Wed, Aug 11, 2021 at 4:45 AM David Hildenbrand <david@...hat.com> wrote:
>>
>> I proposed a while ago to get rid of VM_DENYWRITE completely:
>>
>> https://lkml.kernel.org/r/20210423131640.20080-1-david@redhat.com
>>
>> I haven't looked how much it still applies to current upstream, but
>> maybe that might help cleaning up that code.
> 
> I like it.
> 
> I agree that we could - and probably should - just do it this way.
> 
> We don't expose MAP_DENYWRITE to user space any more - and the old
> legacy library loading code certainly isn't worth it - and so
> effectively the only way to set it is with execve().
> 
> And yes, it gets rid of all the silly games with the per-mapping flags.

I'll rebase, retest and resend, putting you on cc. Then we can discuss 
if/how/when we might want to go that path.

-- 
Thanks,

David / dhildenb