Introduce two related changes to the TrustedBSD MAC Framework:

(1) Abstract interpreter vnode labeling in execve(2) and mac_execve(2)
    so that the general exec code isn't aware of the details of
    allocating, copying, and freeing labels, rather, simply passes in
    a void pointer to start and stop functions that will be used by
    the framework.  This change will be MFC'd.

(2) Introduce a new flags field to the MAC_POLICY_SET(9) interface
    allowing policies to declare which types of objects require label
    allocation, initialization, and destruction, and define a set of
    flags covering various supported object types (MPC_OBJECT_PROC,
    MPC_OBJECT_VNODE, MPC_OBJECT_INPCB, ...).  This change reduces the
    overhead of compiling the MAC Framework into the kernel if policies
    aren't loaded, or if policies require labels on only a small number
    or even no object types.  Each time a policy is loaded or unloaded,
    we recalculate a mask of labeled object types across all policies
    present in the system.  Eliminate MAC_ALWAYS_LABEL_MBUF option as it
    is no longer required.

MFC after:	1 week ((1) only)
Reviewed by:	csjp
Obtained from:	TrustedBSD Project
Sponsored by:	Apple, Inc.

1 files changed, 8 insertions, 3 deletions

diff --git a/sys/security/mac/mac_posix_shm.c b/sys/security/mac/mac_posix_shm.c
index b9da7b3d1ce3..97587ad52133 100644
--- a/sys/security/mac/mac_posix_shm.c
+++ b/sys/security/mac/mac_posix_shm.c
@@ -63,7 +63,10 @@ void
 mac_posixshm_init(struct shmfd *shmfd)
 {
 
-	shmfd->shm_label = mac_posixshm_label_alloc();
+	if (mac_labeled & MPC_OBJECT_POSIXSHM)
+		shmfd->shm_label = mac_posixshm_label_alloc();
+	else
+		shmfd->shm_label = NULL;
 }
 
 static void
@@ -78,8 +81,10 @@ void
 mac_posixshm_destroy(struct shmfd *shmfd)
 {
 
-	mac_posixshm_label_free(shmfd->shm_label);
-	shmfd->shm_label = NULL;
+	if (shmfd->shm_label != NULL) {
+		mac_posixshm_label_free(shmfd->shm_label);
+		shmfd->shm_label = NULL;
+	}
 }
 
 void