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

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Message-ID: <CAHk-=wg6AAX-uXHZnh_Fy=3dMTQYm_j6PKT3m=7xu-FdJOCxng@mail.gmail.com>
Date:   Wed, 11 Aug 2021 06:20:21 -1000
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     David Hildenbrand <david@...hat.com>
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 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.

               Linus