linux-kernel - Re: [PATCH v3 2/7] userns: Simpilify MNT

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Message-ID: <CALCETrXoAi91JN4VLD2ybPgkD_J26=2_N-fyCCjOPL5Swo7kGA@mail.gmail.com>
Date:	Wed, 16 Sep 2015 17:24:47 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Seth Forshee <seth.forshee@...onical.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Jeff Layton <jlayton@...chiereds.net>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	LSM List <linux-security-module@...r.kernel.org>,
	SELinux-NSA <selinux@...ho.nsa.gov>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-mtd@...ts.infradead.org
Subject: Re: [PATCH v3 2/7] userns: Simpilify MNT_NODEV handling.

On Wed, Sep 16, 2015 at 1:02 PM, Seth Forshee
<seth.forshee@...onical.com> wrote:
> From: "Eric W. Biederman" <ebiederm@...ssion.com>
>
> - Consolidate the testing if a device node may be opened in a new
>   function may_open_dev.
>
> - Move the check for allowing access to device nodes on filesystems
>   not mounted in the initial user namespace from mount time to open
>   time and include it in may_open_dev.
>
> This set of changes removes the implicit adding of MNT_NODEV which
> simplifies the logic in fs/namespace.c and removes a potentially
> problematic user visible difference in how normal and unprivileged
> mount namespaces work.
>
> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>

> -               /* Only in special cases allow devices from mounts
> -                * created outside the initial user namespace.
> -                */
> -               if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) {
> -                       flags |= MS_NODEV;
> -                       mnt_flags |= MNT_NODEV | MNT_LOCK_NODEV;
> -               }

This is an ABI change.  It's probably okay, but I think the commit
message should make it clear what's happening.


--Andy
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