linux-kernel - Re: [PATCH 7/8] SELinux: Create a common helper to determine an inode label

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Message-ID: <17513.1434640431@warthog.procyon.org.uk>
Date:	Thu, 18 Jun 2015 16:13:51 +0100
From:	David Howells <dhowells@...hat.com>
To:	Stephen Smalley <sds@...ho.nsa.gov>
Cc:	dhowells@...hat.com, viro@...iv.linux.org.uk, miklos@...redi.hu,
	linux-fsdevel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	linux-unionfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	SELinux <selinux@...ho.nsa.gov>, Paul Moore <paul@...l-moore.com>
Subject: Re: [PATCH 7/8] SELinux: Create a common helper to determine an inode label

Stephen Smalley <sds@...ho.nsa.gov> wrote:

> > +	if ((sbsec->flags & SE_SBINITIALIZED) &&
> > +		   (sbsec->behavior == SECURITY_FS_USE_MNTPOINT)) {
> > +		*_new_isid = sbsec->mntpoint_sid;
> > +	} else if (tsec->create_sid) {
> 
> This doesn't quite match the logic in inode_init_security today, see its
> checking of SBLABEL_MNT.

Fair point.  What does SBLABEL_MNT mean precisely?  It seems to indicate one
of an odd mix of behaviours.  I presume it means that we *have* to calculate a
label and can't get one from the underlying fs if it is not set.

Also, in:

	sbsec->flags |= SE_SBINITIALIZED;
	if (selinux_is_sblabel_mnt(sb))
		sbsec->flags |= SBLABEL_MNT;

should SE_SBINITIALIZED be set after SBLABEL_MNT?  And should there be a
memory barrier in here somewhere before the setting of SE_SBINITIALIZED?

David
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