linux-kernel - Re: [PATCH v8 07/11] proc: flush task dcache entries from all procfs instances

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20200212203833.GQ23230@ZenIV.linux.org.uk>
Date:   Wed, 12 Feb 2020 20:38:33 +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 v8 07/11] proc: flush task dcache entries from all procfs
 instances

On Wed, Feb 12, 2020 at 12:35:04PM -0800, Linus Torvalds wrote:
> On Wed, Feb 12, 2020 at 12:03 PM Al Viro <viro@...iv.linux.org.uk> wrote:
> >
> > What's to prevent racing with fs shutdown while you are doing the second part?
> 
> I was thinking that only the proc_flush_task() code would do this.
> 
> And that holds a ref to the vfsmount through upid->ns.
> 
> So I wasn't suggesting doing this in general - just splitting up the
> implementation of d_invalidate() so that proc_flush_task_mnt() could
> delay the complex part to after having traversed the RCU-protected
> list.
> 
> But hey - I missed this part of the problem originally, so maybe I'm
> just missing something else this time. Wouldn't be the first time.

Wait, I thought the whole point of that had been to allow multiple
procfs instances for the same userns?  Confused...