linux-kernel - Re: VFS, NFS security bug? Should CAP_MKNOD and CAP_LINUX_IMMUTABLE be added to CAP_FS

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Message-ID: <cfd18e0f0903141220u66230ceer22ef0cc6aed1d046@mail.gmail.com>
Date:	Sun, 15 Mar 2009 08:20:17 +1300
From:	Michael Kerrisk <mtk.manpages@...glemail.com>
To:	"J. Bruce Fields" <bfields@...ldses.org>
Cc:	"Serge E. Hallyn" <serue@...ibm.com>,
	Igor Zhbanov <izh1979@...il.com>, linux-kernel@...r.kernel.org,
	viro@...iv.linux.org.uk, neilb@...e.de, Trond.Myklebust@...app.com,
	David Howells <dhowells@...hat.com>,
	James Morris <jmorris@...ei.org>
Subject: Re: VFS, NFS security bug? Should CAP_MKNOD and CAP_LINUX_IMMUTABLE 
	be added to CAP_FS_MASK?

On Sat, Mar 14, 2009 at 6:58 AM, J. Bruce Fields <bfields@...ldses.org> wrote:
> On Fri, Mar 13, 2009 at 09:21:23AM +1300, Michael Kerrisk wrote:
>> On Fri, Mar 13, 2009 at 5:10 AM, Serge E. Hallyn <serue@...ibm.com> wrote:
>> > Quoting J. Bruce Fields (bfields@...ldses.org):
>> >> On Wed, Mar 11, 2009 at 03:53:34PM +0300, Igor Zhbanov wrote:
>> >> > Hello!
>> >> >
>> >> > It seems that CAP_MKNOD and CAP_LINUX_IMMUTABLE were forgotten to be
>> >> > added to CAP_FS_MASK_B0 in linux-2.6.x and to CAP_FS_MASK in
>> >> > linux-2.4.x. Both capabilities affects file system and can be
>> >> > considered file system capabilities.
>> >>
>> >> Sounds right to me--I'd expect rootsquash to guarantee that new device
>> >> nodes can't be created from the network.  Cc'ing random people from the
>> >> git log for include/linux/capability.h in hopes they can help.
>> >
>> > Yeah it seems reasonable.  If it is, then does that mean that we
>> > also need CAP_SYS_ADMIN (to write selinux labels) and CAP_SETFCAP
>> > (to set file capabilities) as well?
>>
>> If a change is made to CAP_FS_MASK, please do remember to CC
>> mtk.manpages@...il.com, and linux-api@.
>
> OK, that's because the exact set of capabilities that is dropped on
> setfsuid is documented in capabilities(7)?  (Anywhere else?)

Not that I know of.


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
git://git.kernel.org/pub/scm/docs/man-pages/man-pages.git
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