On 11/1/2013 1:05 PM, Myklebust, Trond wrote:
On Nov 1, 2013, at 12:57, Jeff Layton <jlayton@xxxxxxxxxx> wrote:
On Fri, 1 Nov 2013 16:50:00 +0000
"Myklebust, Trond" <Trond.Myklebust@xxxxxxxxxx> wrote:
On Fri, 2013-11-01 at 12:02 -0400, Jeff Layton wrote:
It looks like _nfs4_get_security_label() has the same problem, but I've
so far been unable to get it to be called, so I didn't patch it. It
seems like getxattr does some special stuff for SELinux labels that
cause them only to ever be fetched once.
Is there some trick to it?
Doesn't 'ls -Z' cause them to security label to be read again?
As best I can tell, security labels are set on the inode when the inode
is instantiated, and then are reset on changes (i.e. setxattr). If
…and on getxattr, afaics.
another client changes the label though, it's not clear to me how your
client would ever notice it until the inode is dropped from the cache.
ISTR Eric Paris explaining to me that they do that for performance
reasons but it seems like something that needs to be reconsidered in
light of labeled NFS. Not picking up a security label change seems like
a bug, IMO...
To be effective, the security label should normally be set at file creation time. It should rarely, if ever, change. Why would you need to change it from a different client?
Cheers,
Trond
That isn't completely true. Security labels should be set on creation
but they may change. An SELinux label consists of
user:role:type:level/categories. In RHEL and Fedora level/categories
implements something called multi category security. One level multiple
categories with the constraint on categories being that all must match
for access to be allowed. This is how sVirt work. It picks two
categories and setups the qemu process to start with these categories
and then manipulates the files on disk to have these categories such
that even though the qemu_t proess can access the files type enforcement
wise the categories deny it. Its what allows for SELinux based per
process separation of a type.
Dave
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
