selinux: add support for xperms in conditional policies

Add support for extended permission rules in conditional policies.
Currently the kernel accepts such rules already, but evaluating a
security decision will hit a BUG() in
services_compute_xperms_decision().  Thus reject extended permission
rules in conditional policies for current policy versions.

Add a new policy version for this feature.

Signed-off-by: Christian Göttsche <[email protected]>
Acked-by: Stephen Smalley <[email protected]>
Tested-by: Stephen Smalley <[email protected]>
Signed-off-by: Paul Moore <[email protected]>

Author: cgzones

security/selinux/include/security.h

@@ -46,10 +46,11 @@
 #define POLICYDB_VERSION_INFINIBAND	     31
 #define POLICYDB_VERSION_GLBLUB		     32
 #define POLICYDB_VERSION_COMP_FTRANS	     33 /* compressed filename transitions */
+#define POLICYDB_VERSION_COND_XPERMS	     34 /* extended permissions in conditional policies */
 
 /* Range of policy versions we understand*/
 #define POLICYDB_VERSION_MIN POLICYDB_VERSION_BASE
-#define POLICYDB_VERSION_MAX POLICYDB_VERSION_COMP_FTRANS
+#define POLICYDB_VERSION_MAX POLICYDB_VERSION_COND_XPERMS
 
 /* Mask for just the mount related flags */
 #define SE_MNTMASK 0x0f

security/selinux/ss/avtab.c

@@ -339,7 +339,7 @@ static const uint16_t spec_order[] = {
 int avtab_read_item(struct avtab *a, void *fp, struct policydb *pol,
 		    int (*insertf)(struct avtab *a, const struct avtab_key *k,
 				   const struct avtab_datum *d, void *p),
-		    void *p)
+		    void *p, bool conditional)
 {
 	__le16 buf16[4];
 	u16 enabled;
@@ -457,6 +457,13 @@ int avtab_read_item(struct avtab *a, void *fp, struct policydb *pol,
 		       "was specified\n",
 		       vers);
 		return -EINVAL;
+	} else if ((vers < POLICYDB_VERSION_COND_XPERMS) &&
+		   (key.specified & AVTAB_XPERMS) && conditional) {
+		pr_err("SELinux:  avtab:  policy version %u does not "
+		       "support extended permissions rules in conditional "
+		       "policies and one was specified\n",
+		       vers);
+		return -EINVAL;
 	} else if (key.specified & AVTAB_XPERMS) {
 		memset(&xperms, 0, sizeof(struct avtab_extended_perms));
 		rc = next_entry(&xperms.specified, fp, sizeof(u8));
@@ -523,7 +530,7 @@ int avtab_read(struct avtab *a, void *fp, struct policydb *pol)
 		goto bad;
 
 	for (i = 0; i < nel; i++) {
-		rc = avtab_read_item(a, fp, pol, avtab_insertf, NULL);
+		rc = avtab_read_item(a, fp, pol, avtab_insertf, NULL, false);
 		if (rc) {
 			if (rc == -ENOMEM)
 				pr_err("SELinux: avtab: out of memory\n");

security/selinux/ss/avtab.h

@@ -108,7 +108,7 @@ struct policydb;
 int avtab_read_item(struct avtab *a, void *fp, struct policydb *pol,
 		    int (*insert)(struct avtab *a, const struct avtab_key *k,
 				  const struct avtab_datum *d, void *p),
-		    void *p);
+		    void *p, bool conditional);
 
 int avtab_read(struct avtab *a, void *fp, struct policydb *pol);
 int avtab_write_item(struct policydb *p, const struct avtab_node *cur,

security/selinux/ss/conditional.c

@@ -349,7 +349,7 @@ static int cond_read_av_list(struct policydb *p, void *fp,
 	for (i = 0; i < len; i++) {
 		data.dst = &list->nodes[i];
 		rc = avtab_read_item(&p->te_cond_avtab, fp, p, cond_insertf,
-				     &data);
+				     &data, true);
 		if (rc) {
 			kfree(list->nodes);
 			list->nodes = NULL;

security/selinux/ss/policydb.c

@@ -155,6 +155,11 @@ static const struct policydb_compat_info policydb_compat[] = {
 		.sym_num = SYM_NUM,
 		.ocon_num = OCON_NUM,
 	},
+	{
+		.version = POLICYDB_VERSION_COND_XPERMS,
+		.sym_num = SYM_NUM,
+		.ocon_num = OCON_NUM,
+	},
 };
 
 static const struct policydb_compat_info *

security/selinux/ss/services.c

@@ -946,7 +946,7 @@ static void avd_init(struct selinux_policy *policy, struct av_decision *avd)
 }
 
 static void update_xperms_extended_data(u8 specified,
-					struct extended_perms_data *from,
+					const struct extended_perms_data *from,
 					struct extended_perms_data *xp_data)
 {
 	unsigned int i;
@@ -967,6 +967,8 @@ static void update_xperms_extended_data(u8 specified,
 void services_compute_xperms_decision(struct extended_perms_decision *xpermd,
 					struct avtab_node *node)
 {
+	u16 specified;
+
 	switch (node->datum.u.xperms->specified) {
 	case AVTAB_XPERMS_IOCTLFUNCTION:
 	case AVTAB_XPERMS_NLMSG:
@@ -982,17 +984,19 @@ void services_compute_xperms_decision(struct extended_perms_decision *xpermd,
 		BUG();
 	}
 
-	if (node->key.specified == AVTAB_XPERMS_ALLOWED) {
+	specified = node->key.specified & ~(AVTAB_ENABLED | AVTAB_ENABLED_OLD);
+
+	if (specified == AVTAB_XPERMS_ALLOWED) {
 		xpermd->used |= XPERMS_ALLOWED;
 		update_xperms_extended_data(node->datum.u.xperms->specified,
 					    &node->datum.u.xperms->perms,
 					    xpermd->allowed);
-	} else if (node->key.specified == AVTAB_XPERMS_AUDITALLOW) {
+	} else if (specified == AVTAB_XPERMS_AUDITALLOW) {
 		xpermd->used |= XPERMS_AUDITALLOW;
 		update_xperms_extended_data(node->datum.u.xperms->specified,
 					    &node->datum.u.xperms->perms,
 					    xpermd->auditallow);
-	} else if (node->key.specified == AVTAB_XPERMS_DONTAUDIT) {
+	} else if (specified == AVTAB_XPERMS_DONTAUDIT) {
 		xpermd->used |= XPERMS_DONTAUDIT;
 		update_xperms_extended_data(node->datum.u.xperms->specified,
 					    &node->datum.u.xperms->perms,