From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <owner-linux-mm@kvack.org>
Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69])
	by kanga.kvack.org (Postfix) with ESMTP id EEC238E0002
	for <linux-mm@kvack.org>; Wed, 16 Jan 2019 20:49:33 -0500 (EST)
Received: by mail-wr1-f69.google.com with SMTP id v16so3940022wru.8
        for <linux-mm@kvack.org>; Wed, 16 Jan 2019 17:49:33 -0800 (PST)
Received: from nautica.notk.org (ipv6.notk.org. [2001:41d0:1:7a93::1])
        by mx.google.com with ESMTPS id r1si24500514wmr.17.2019.01.16.17.49.31
        for <linux-mm@kvack.org>
        (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128);
        Wed, 16 Jan 2019 17:49:32 -0800 (PST)
Date: Thu, 17 Jan 2019 02:49:16 +0100
From: Dominique Martinet <asmadeus@codewreck.org>
Subject: Re: [PATCH] mm/mincore: allow for making sys_mincore() privileged
Message-ID: <20190117014916.GA10968@nautica>
References: <CAHk-=wip2CPrdOwgF0z4n2tsdW7uu+Egtcx9Mxxe3gPfPW_JmQ@mail.gmail.com>
 <5c3e7de6.1c69fb81.4aebb.3fec@mx.google.com>
 <CAHk-=wgF9p9xNzZei_-ejGLy1bJf4VS1C5E9_V0kCTEpCkpCTQ@mail.gmail.com>
 <9E337EA6-7CDA-457B-96C6-E91F83742587@amacapital.net>
 <CAHk-=wjqkbjL2_BwUYxJxJhdadiw6Zx-Yu_mK3E6P7kG3wSGcQ@mail.gmail.com>
 <20190116054613.GA11670@nautica>
 <CAHk-=wjVjecbGRcxZUSwoSgAq9ZbMxbA=MOiqDrPgx7_P3xGhg@mail.gmail.com>
 <nycvar.YFH.7.76.1901161710470.6626@cbobk.fhfr.pm>
 <CAHk-=wgsnWvSsMfoEYzOq6fpahkHWxF3aSJBbVqywLa34OXnLg@mail.gmail.com>
 <nycvar.YFH.7.76.1901162120000.6626@cbobk.fhfr.pm>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <nycvar.YFH.7.76.1901162120000.6626@cbobk.fhfr.pm>
Sender: owner-linux-mm@kvack.org
List-ID: <linux-mm.kvack.org>
To: Jiri Kosina <jikos@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>, Andy Lutomirski <luto@amacapital.net>, Josh Snyder <joshs@netflix.com>, Dave Chinner <david@fromorbit.com>, Matthew Wilcox <willy@infradead.org>, Jann Horn <jannh@google.com>, Andrew Morton <akpm@linux-foundation.org>, Greg KH <gregkh@linuxfoundation.org>, Peter Zijlstra <peterz@infradead.org>, Michal Hocko <mhocko@suse.com>, Linux-MM <linux-mm@kvack.org>, kernel list <linux-kernel@vger.kernel.org>, Linux API <linux-api@vger.kernel.org>

Jiri Kosina wrote on Wed, Jan 16, 2019:
> So if noone sees any principal problem there, I'll happily submit it with 
> proper attribution etc.

I'm not convinced just the write permission check is enough for
mincore(), as Josh also seems to share the concern I raised (e.g. map a
git directory "hot" pages)
We probably need to add an inode_owner_or_capable() or similar, the open
question is do we still need the write access check after that - I don't
really know how expensive these calls are.

Thanks,
-- 
Dominique