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From: David Howells <dhowells@redhat.com>
In-Reply-To: <12076.1417097856@warthog.procyon.org.uk>
References: <12076.1417097856@warthog.procyon.org.uk> <545A6464.5070702@tycho.nsa.gov> <20141105154217.2555.578.stgit@warthog.procyon.org.uk> <20141105154318.2555.7052.stgit@warthog.procyon.org.uk> <545A53A9.4060009@tycho.nsa.gov>
Cc: dhowells@redhat.com, Stephen Smalley <sds@tycho.nsa.gov>,
        linux-unionfs@vger.kernel.org, selinux@tycho.nsa.gov,
        linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 6/7] SELinux: The copy-up operation must have read permission on the lower file
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Date: Thu, 27 Nov 2014 14:21:36 +0000
Message-ID: <12173.1417098096@warthog.procyon.org.uk>
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David Howells <dhowells@redhat.com> wrote:

> > This means that it expects to trigger those capability checks as part of
> > its subsequent actions.  Raising those capabilities temporarily in its
> > credentials will pass the capability module checks but won't address the
> > corresponding SELinux checks (both capability and file-based), so you'll
> > end up triggering an entire set of checks against the current process'
> > credentials.  This same pattern is repeated elsewhere in overlayfs.
> 
> Hmmm...  Yes.  I need to check whether the lower file can be read *before*
> overriding the creds.

Actually, I think ovl_permission() does sufficient checks on the lower inode
by calling __inode_permission() upon it.

David
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