linux-kernel - Re: [PATCH v2] Add security.* XATTR support for the UBIFS

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Date:	Wed, 11 Apr 2012 09:10:53 -0400
From:	Stephen Smalley <sds@...ho.nsa.gov>
To:	Subodh Nijsure <subodh.nijsure@...il.com>
Cc:	linux-mtd@...ts.infradead.org,
	Artem Bityutskiy <dedekind1@...il.com>, casey@...aufler-ca.com,
	Adrian Hunter <adrian.hunter@...el.com>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	Subodh Nijsure <snijsure@...d-net.com>
Subject: Re: [PATCH v2] Add security.* XATTR support for the UBIFS

On Wed, 2012-04-11 at 06:00 -0700, Subodh Nijsure wrote:
> On Tue, Apr 10, 2012 at 5:46 AM, Stephen Smalley <sds@...ho.nsa.gov> wrote:
> > On Mon, 2012-04-09 at 16:51 -0700, subodh.nijsure@...il.com wrote:
> >> From: Subodh Nijsure <snijsure@...d-net.com>
> >>
> >> Also fix couple of bugs in UBIFS extended attribute length calculation.
> >>
> >> Changes Since V1:
> >>          Instead of just handling security.selinux extended attribute handle
> >>          all security.* attributes.
> >>
> >> TESTING: Tested on  MX28 based platforms using Micron MT29F2G08ABAEAH4 NAND
> >>          With these change we are able to label UBIFS filesystem with
> >>          security.selinux and run system with selinux enabled.
> >>          This change also allows one to set other security.* extended
> >>          attributesr, such as security.smack security.evm, security.ima
> >>          Ran integck test on UBI filesystem.
> >>
> >> Signed-off-by: Subodh Nijsure <snijsure@...d-net.com>
> >> ---
> >>  fs/ubifs/dir.c     |    4 ++
> >>  fs/ubifs/file.c    |    6 ++
> >>  fs/ubifs/journal.c |   12 +++-
> >>  fs/ubifs/super.c   |    3 +
> >>  fs/ubifs/ubifs.h   |    9 +++
> >>  fs/ubifs/xattr.c   |  147 ++++++++++++++++++++++++++++++++++++++++++++++++----
> >>  6 files changed, 167 insertions(+), 14 deletions(-)
> >>
> >> diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
> >> index ec9f187..f4e06c4 100644
> >> --- a/fs/ubifs/dir.c
> >> +++ b/fs/ubifs/dir.c
> >> @@ -293,6 +293,7 @@ static int ubifs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
> >>       ubifs_release_budget(c, &req);
> >>       insert_inode_hash(inode);
> >>       d_instantiate(dentry, inode);
> >> +     ubifs_init_security(dir, inode, &dentry->d_name);
> >>       return 0;
> >>
> >>  out_cancel:
> >
> > The ubifs_init_security() should occur before d_instantiate() so that
> > the inode is not accessible to other threads before its security
> > attributes have been set.  And if it fails, you would ideally drop the
> > inode altogether and return an error to the creating process.
> >
> 
> I will look into moving ubifs_init_security() before d_instantiate().
> Last time I had tried I had run into some issues and had to keep
> creating inode and then creating xattr as two seperate items. I will
> look through the UBIFS code that actually creates xattr ubi nodes.
> Also I will wait for couple of days to send v3 patch with to see if
> mtd folks have other comments this patch.

I'd favor moving the call to ubifs_init_security() inside of
ubifs_new_inode() so that it gets done as part of all inode creation.
To do that, you'll need to pass the &dentry->d_name (const struct qstr
*) down to ubifs_new_inode(). But you can see that it is done that way
for ext4_new_inode(), for example.

-- 
Stephen Smalley
National Security Agency

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