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Date:   Fri, 20 Aug 2021 09:30:31 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Jeff Layton <jlayton@kernel.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Matthew Wilcox <willy@infradead.org>,
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        Miklos Szeredi <miklos@szeredi.hu>,
        Chengguang Xu <cgxu519@mykernel.net>,
        Christian =?iso-8859-1?Q?K=F6nig?= 
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Subject: Re: Removing Mandatory Locks
Message-ID: <202108200905.BE8AF7C@keescook>
References: <CAHk-=wgru1UAm3kAKSOdnbewPXQMOxYkq9PnAsRadAC6pXCCMQ@mail.gmail.com>
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 <87h7ft2j68.fsf@disp2133>
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 <b629cda1-becd-4725-b16c-13208ff478d3@www.fastmail.com>
 <YRcyqbpVqwwq3P6n@casper.infradead.org>
 <87k0kkxbjn.fsf_-_@disp2133>
 <0c2af732e4e9f74c9d20b09fc4b6cbae40351085.camel@kernel.org>
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On Thu, Aug 19, 2021 at 12:15:08PM -0700, Linus Torvalds wrote:
> On Thu, Aug 19, 2021 at 11:39 AM Jeff Layton <jlayton@kernel.org> wrote:
> >
> > I'm all for ripping it out too. It's an insane interface anyway.
> >
> > I've not heard a single complaint about this being turned off in
> > fedora/rhel or any other distro that has this disabled.
> 
> I'd love to remove it, we could absolutely test it. The fact that
> several major distros have it disabled makes me think it's fine.

FWIW, it is now disabled in Ubuntu too:

https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/impish/commit/?h=master-next&id=f3aac5e47789cbeb3177a14d3d2a06575249e14b

> But as always, it would be good to check Android.

It looks like it's enabled (checking the Pixel 4 kernel image), but it's
not specifically mentioned in any of the build configs that are used to
construct the image, so I think this is just catching the "default y". I
expect it'd be fine to turn this off.

I will ask around to see if it's actually used.

-- 
Kees Cook