Continue work to optimize performance of "options MAC" when no MAC policy

modules are loaded by avoiding mbuf label lookups when policies aren't
loaded, pushing further socket locking into MAC policy modules, and
avoiding locking MAC ifnet locks when no policies are loaded:

- Check mac_policies_count before looking for mbuf MAC label m_tags in MAC
  Framework entry points.  We will still pay label lookup costs if MAC
  policies are present but don't require labels (typically a single mbuf
  header field read, but perhaps further indirection if IPSEC or other
  m_tag consumers are in use).

- Further push socket locking for socket-related access control checks and
  events into MAC policies from the MAC Framework, so that sockets are
  only locked if a policy specifically requires a lock to protect a label.
  This resolves lock order issues during sonewconn() and also in local
  domain socket cross-connect where multiple socket locks could not be
  held at once for the purposes of propagatig MAC labels across multiple
  sockets.  Eliminate mac_policy_count check in some entry points where it
  no longer avoids locking.

- Add mac_policy_count checking in some entry points relating to network
  interfaces that otherwise lock a global MAC ifnet lock used to protect
  ifnet labels.

Obtained from:	TrustedBSD Project

1 files changed, 15 insertions, 0 deletions

diff --git a/sys/security/mac/mac_net.c b/sys/security/mac/mac_net.c
index ecd4195..73154148 100644
--- a/sys/security/mac/mac_net.c
+++ b/sys/security/mac/mac_net.c
@@ -296,6 +296,9 @@ void
 mac_ifnet_create(struct ifnet *ifp)
 {
 
+	if (mac_policy_count == 0)
+		return;
+
 	MAC_IFNET_LOCK(ifp);
 	MAC_POLICY_PERFORM_NOSLEEP(ifnet_create, ifp, ifp->if_label);
 	MAC_IFNET_UNLOCK(ifp);
@@ -315,6 +318,9 @@ mac_bpfdesc_create_mbuf(struct bpf_d *d, struct mbuf *m)
 
 	BPFD_LOCK_ASSERT(d);
 
+	if (mac_policy_count == 0)
+		return;
+
 	label = mac_mbuf_to_label(m);
 
 	MAC_POLICY_PERFORM_NOSLEEP(bpfdesc_create_mbuf, d, d->bd_label, m,
@@ -326,6 +332,9 @@ mac_ifnet_create_mbuf(struct ifnet *ifp, struct mbuf *m)
 {
 	struct label *label;
 
+	if (mac_policy_count == 0)
+		return;
+
 	label = mac_mbuf_to_label(m);
 
 	MAC_IFNET_LOCK(ifp);
@@ -344,6 +353,9 @@ mac_bpfdesc_check_receive(struct bpf_d *d, struct ifnet *ifp)
 
 	BPFD_LOCK_ASSERT(d);
 
+	if (mac_policy_count == 0)
+		return (0);
+
 	MAC_IFNET_LOCK(ifp);
 	MAC_POLICY_CHECK_NOSLEEP(bpfdesc_check_receive, d, d->bd_label, ifp,
 	    ifp->if_label);
@@ -364,6 +376,9 @@ mac_ifnet_check_transmit(struct ifnet *ifp, struct mbuf *m)
 
 	M_ASSERTPKTHDR(m);
 
+	if (mac_policy_count == 0)
+		return (0);
+
 	label = mac_mbuf_to_label(m);
 
 	MAC_IFNET_LOCK(ifp);