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

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Message-ID: <20190117014916.GA10968@nautica>
Date:   Thu, 17 Jan 2019 02:49:16 +0100
From:   Dominique Martinet <asmadeus@...ewreck.org>
To:     Jiri Kosina <jikos@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Josh Snyder <joshs@...flix.com>,
        Dave Chinner <david@...morbit.com>,
        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

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