linux-kernel - Re: [PATCH 0/7] proc: Dentry flushing without proc

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Message-ID: <20200220230758.GT23230@ZenIV.linux.org.uk>
Date:   Thu, 20 Feb 2020 23:07:58 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        Linux API <linux-api@...r.kernel.org>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        Linux Security Module <linux-security-module@...r.kernel.org>,
        Akinobu Mita <akinobu.mita@...il.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Daniel Micay <danielmicay@...il.com>,
        Djalal Harouni <tixxdz@...il.com>,
        "Dmitry V . Levin" <ldv@...linux.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        "J . Bruce Fields" <bfields@...ldses.org>,
        Jeff Layton <jlayton@...chiereds.net>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Solar Designer <solar@...nwall.com>
Subject: Re: [PATCH 0/7] proc: Dentry flushing without proc_mnt

On Thu, Feb 20, 2020 at 03:02:22PM -0800, Linus Torvalds wrote:
> On Thu, Feb 20, 2020 at 12:48 PM Eric W. Biederman
> <ebiederm@...ssion.com> wrote:
> >
> > Linus, does this approach look like something you can stand?
> 
> A couple of worries, although one of them seem to have already been
> resolved by Al.
> 
> I think the real gatekeeper should be Al in general.  But other than
> the small comments I had, I think this might work just fine.
> 
> Al?

I'll need to finish RTFS there; I have initially misread that patch,
actually - Eric _is_ using that thing both for those directories
and for sysctl inodes.  And the prototype for that machinery (the
one he'd pulled from proc_sysctl.c) is playing with pinning superblocks
way too much; for per-pid directories that's not an issue, but
for sysctl table removal you are very likely to hit a bunch of
evictees on the same superblock...