apparmor: extend policydb permission set by making use of the xbits

The policydb permission set has left the xbits unused. Make them
available for mediation.

Note: that this does not bring full auditing control of the
permissions as there are not enough bits. The quieting of denials is
provided as that is used more than forced auditing of allowed
permissions.
Signed-off-by: John Johansen <john.johansen@canonical.com>

security/apparmor/policy_unpack.c

@@ -38,6 +38,7 @@
 #define v6	6	/* per entry policydb mediation check */
 #define v7	7
 #define v8	8	/* full network masking */
+#define v9	9	/* xbits are used as permission bits in policydb */
 
 /*
  * The AppArmor interface treats data as a type byte followed by the
@@ -796,6 +797,12 @@ static u32 map_other(u32 x)
 		((x & 0x60) << 19);	/* SETOPT/GETOPT */
 }
 
+static u32 map_xbits(u32 x)
+{
+	return ((x & 0x1) << 7) |
+		((x & 0x7e) << 9);
+}
+
 static struct aa_perms compute_perms_entry(struct aa_dfa *dfa,
 					   aa_state_t state,
 					   u32 version)
@@ -806,15 +813,31 @@ static struct aa_perms compute_perms_entry(struct aa_dfa *dfa,
 	perms.audit = dfa_user_audit(dfa, state);
 	perms.quiet = dfa_user_quiet(dfa, state);
 
-	/* for v5 perm mapping in the policydb, the other set is used
-	 * to extend the general perm set
+	/*
+	 * This mapping is convulated due to history.
+	 * v1-v4: only file perms, which are handled by compute_fperms
+	 * v5: added policydb which dropped user conditional to gain new
+	 *     perm bits, but had to map around the xbits because the
+	 *     userspace compiler was still munging them.
+	 * v9: adds using the xbits in policydb because the compiler now
+	 *     supports treating policydb permission bits different.
+	 *     Unfortunately there is no way to force auditing on the
+	 *     perms represented by the xbits
 	 */
-
 	perms.allow |= map_other(dfa_other_allow(dfa, state));
 	if (VERSION_LE(version, v8))
 		perms.allow |= AA_MAY_LOCK;
+	else
+		perms.allow |= map_xbits(dfa_user_xbits(dfa, state));
+
+	/*
+	 * for v5-v9 perm mapping in the policydb, the other set is used
+	 * to extend the general perm set
+	 */
 	perms.audit |= map_other(dfa_other_audit(dfa, state));
 	perms.quiet |= map_other(dfa_other_quiet(dfa, state));
+	if (VERSION_GT(version, v8))
+		perms.quiet |= map_xbits(dfa_other_xbits(dfa, state));
 
 	return perms;
 }
@@ -1188,7 +1211,7 @@ static int verify_header(struct aa_ext *e, int required, const char **ns)
 	 * if not specified use previous version
 	 * Mask off everything that is not kernel abi version
 	 */
-	if (VERSION_LT(e->version, v5) || VERSION_GT(e->version, v8)) {
+	if (VERSION_LT(e->version, v5) || VERSION_GT(e->version, v9)) {
 		audit_iface(NULL, NULL, NULL, "unsupported interface version",
 			    e, error);
 		return error;