NetLabel: Allow passing the LSM domain as a shared pointer

Smack doesn't have the need to create a private copy of the LSM "domain" when
setting NetLabel security attributes like SELinux, however, the current
NetLabel code requires a private copy of the LSM "domain".  This patches fixes
that by letting the LSM determine how it wants to pass the domain value.

 * NETLBL_SECATTR_DOMAIN_CPY
   The current behavior, NetLabel assumes that the domain value is a copy and
   frees it when done

 * NETLBL_SECATTR_DOMAIN
   New, Smack-friendly behavior, NetLabel assumes that the domain value is a
   reference to a string managed by the LSM and does not free it when done

Signed-off-by: Paul Moore <paul.moore@hp.com>
Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 732ba27..e2d6f7c 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -1275,7 +1275,7 @@
 
 	switch (smack_net_nltype) {
 	case NETLBL_NLTYPE_CIPSOV4:
-		nlsp->domain = kstrdup(smack, GFP_ATOMIC);
+		nlsp->domain = smack;
 		nlsp->flags = NETLBL_SECATTR_DOMAIN | NETLBL_SECATTR_MLS_LVL;
 
 		rc = smack_to_cipso(smack, &cipso);