linux-kernel - Re: [PATCH v3 1/3] nsproxy: add struct nsset

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Date:   Mon, 4 May 2020 18:25:17 +0200
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     linux-kernel@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Stéphane Graber <stgraber@...ntu.com>,
        Linux Containers <containers@...ts.linux-foundation.org>,
        Serge Hallyn <serge@...lyn.com>, Jann Horn <jannh@...gle.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Aleksa Sarai <cyphar@...har.com>, linux-api@...r.kernel.org
Subject: Re: [PATCH v3 1/3] nsproxy: add struct nsset

On Mon, May 04, 2020 at 11:15:54AM -0500, Eric W. Biederman wrote:
> Christian Brauner <christian.brauner@...ntu.com> writes:
> 
> > Add a simple struct nsset. It holds all necessary pieces to switch to a new
> > set of namespaces without leaving a task in a half-switched state which we
> > will make use of in the next patch. This patch simply switches the existing
> > setns logic over without causing a change in setns() behavior. This brings
> > setns() closer to how unshare() works(). The prepare_ns() function is
> > responsible to prepare all necessary information. This has two reasons.
> > First it minimizes dependencies between individual namespaces, i.e. all
> > install handler can expect that all fields are properly initialized
> > independent in what order they are called in. Second, this makes the code
> > easier to maintain and easier to follow if it needs to be changed.
> 
> This is buggy.
> 
> Your code assume that nstype == 0 is invalid.

Yep, good catch! That's a bug from rearranging the patches.

> 
> Passing nstype == 0 means don't verify the kind of file descriptor
> passed.
> 
> Quite frankly doing nstype & CLONE_XYZ is wrong.  It always
> needs to be nstype == CLONE_XYZ.

I mean, I can do the nstype == CLONE_NEW* in the preparatory patch and
then switch to flags & CLONE_NEW* later.

Let me fix this right now.

Christian