linux-kernel - Re: [PATCH] mm/mincore: allow for making sys

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Message-ID: <CAHk-=wjqkbjL2_BwUYxJxJhdadiw6Zx-Yu_mK3E6P7kG3wSGcQ@mail.gmail.com>
Date:   Wed, 16 Jan 2019 17:34:01 +1200
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Andy Lutomirski <luto@...capital.net>
Cc:     Josh Snyder <joshs@...flix.com>,
        Dominique Martinet <asmadeus@...ewreck.org>,
        Dave Chinner <david@...morbit.com>,
        Jiri Kosina <jikos@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Jann Horn <jannh@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Michal Hocko <mhocko@...e.com>, Linux-MM <linux-mm@...ck.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH] mm/mincore: allow for making sys_mincore() privileged

On Wed, Jan 16, 2019 at 5:25 PM Andy Lutomirski <luto@...capital.net> wrote:
>
> Something like CAP_DAC_READ_SEARCH might not be crazy.

I agree that it would work. In fact' it's what Jiri's patch basically
did. Except Jiri used CAP_SYS_ADMIN instead.

But that then basically limits it to root (or root-like with
capability masks), which is quite likely to not work in practice all
that well. That's why I wanted to find alternatives.

*Very* few people want to run their databases as root.

Jiri's original patch kind of acknowledged that by making the new test
be conditional, and off by default. So then it's a "only do this for
lockdown mode, because normal people won't find it acceptable".

And I'm not a huge fan of that approach. If you don't protect normal
people, then what's the point, really?

              Linus