linux-kernel - Re: [RESEND PATCH v4 0/3] proc: Relax check of mount visibility

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Message-ID: <20210310182229.dynrgsxejnfkp3f2@example.org>
Date:   Wed, 10 Mar 2021 19:22:29 +0100
From:   Alexey Gladkov <gladkov.alexey@...il.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [RESEND PATCH v4 0/3] proc: Relax check of mount visibility

On Mon, Feb 22, 2021 at 09:44:40AM -0600, Eric W. Biederman wrote:
> Alexey Gladkov <gladkov.alexey@...il.com> writes:
> 
> > If only the dynamic part of procfs is mounted (subset=pid), then there is no
> > need to check if procfs is fully visible to the user in the new user
> > namespace.
> 
> 
> A couple of things.
> 
> 1) Allowing the mount should come in the last patch.  So we don't have a
> bisect hazard.
> 
> 2) We should document that we still require a mount of proc to match on
> atime and readonly mount attributes.

Ok. I will try to do it in v5.

> 3) If we can find a way to safely not require a previous mount of proc
> this will be much more valuable.

True, but for now I have no idea how to do it. I would prefer to move in
small steps.

-- 
Rgrds, legion