Fix LOR between the syncache and inpcb locks when MAC is present in the

kernel.  This LOR snuck in with some of the recent syncache changes.  To
fix this, the inpcb handling was changed:

- Hang a MAC label off the syncache object
- When the syncache entry is initially created, we pickup the PCB lock
  is held because we extract information from it while initializing the
  syncache entry.  While we do this, copy the MAC label associated with
  the PCB and use it for the syncache entry.
- When the packet is transmitted, copy the label from the syncache entry
  to the mbuf so it can be processed by security policies which analyze
  mbuf labels.

This change required that the MAC framework be extended to support the
label copy operations from the PCB to the syncache entry, and then from
the syncache entry to the mbuf.

These functions really should be referencing the syncache structure instead
of the label.  However, due to some of the complexities associated with
exposing this syncache structure we operate directly on it's label pointer.
This should be OK since we aren't making any access control decisions within
this code directly, we are merely allocating and copying label storage so
we can properly initialize mbuf labels for any packets the syncache code
might create.

This also has a nice side effect of caching.  Prior to this change, the
PCB would be looked up/locked for each packet transmitted.  Now the label
is cached at the time the syncache entry is initialized.

Submitted by:	andre [1]
Discussed with:	rwatson

[1] andre submitted the tcp_syncache.c changes

1 files changed, 54 insertions, 0 deletions

diff --git a/sys/security/mac/mac_inet.c b/sys/security/mac/mac_inet.c
index 0d35e48..7896332 100644
--- a/sys/security/mac/mac_inet.c
+++ b/sys/security/mac/mac_inet.c
@@ -288,3 +288,57 @@ mac_create_mbuf_from_firewall(struct mbuf *m)
 	label = mac_mbuf_to_label(m);
 	MAC_PERFORM(create_mbuf_from_firewall, m, label);
 }
+
+/*
+ * These functions really should be referencing the syncache structure instead
+ * of the label.  However, due to some of the complexities associated with
+ * exposing this syncache structure we operate directly on it's label pointer.
+ * This should be OK since we aren't making any access control decisions within
+ * this code directly, we are merely allocating and copying label storage so
+ * we can properly initialize mbuf labels for any packets the syncache code
+ * might create.
+ */
+void
+mac_destroy_syncache(struct label **label)
+{
+
+	MAC_PERFORM(destroy_syncache_label, *label);
+	mac_labelzone_free(*label);
+	*label = NULL;
+}
+
+int
+mac_init_syncache(struct label **label)
+{
+	int error;
+
+	*label = mac_labelzone_alloc(M_NOWAIT);
+	if (*label == NULL)
+		return (ENOMEM);
+	/*
+	 * Since we are holding the inpcb locks the policy can not allocate
+	 * policy specific label storage using M_WAITOK.  So we need to do a
+	 * MAC_CHECK instead of the typical MAC_PERFORM so we can propagate
+	 * allocation failures back to the syncache code.
+	 */
+	MAC_CHECK(init_syncache_label, *label, M_NOWAIT);
+	return (error);
+}
+
+void
+mac_init_syncache_from_inpcb(struct label *label, struct inpcb *inp)
+{
+
+	INP_LOCK_ASSERT(inp);
+	MAC_PERFORM(init_syncache_from_inpcb, label, inp);
+}
+
+void
+mac_create_mbuf_from_syncache(struct label *sc_label, struct mbuf *m)
+{
+	struct label *mbuf_label;
+
+	M_ASSERTPKTHDR(m);
+	mbuf_label = mac_mbuf_to_label(m);
+	MAC_PERFORM(create_mbuf_from_syncache, sc_label, m, mbuf_label);
+}