selinux: allow MLS->non-MLS and vice versa upon policy reload

Allow runtime switching between different policy types (e.g. from a MLS/MCS
policy to a non-MLS/non-MCS policy or viceversa).
Signed-off-by: Guido Trentalancia <guido@trentalancia.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>

security/selinux/include/security.h

@@ -57,7 +57,6 @@
 struct netlbl_lsm_secattr;
 
 extern int selinux_enabled;
-extern int selinux_mls_enabled;
 
 /* Policy capabilities */
 enum {
@@ -80,6 +79,8 @@ extern int selinux_policycap_openperm;
 /* limitation of boundary depth  */
 #define POLICYDB_BOUNDS_MAXDEPTH	4
 
+int security_mls_enabled(void);
+
 int security_load_policy(void *data, size_t len);
 
 int security_policycap_supported(unsigned int req_cap);

security/selinux/selinuxfs.c

@@ -282,7 +282,8 @@ static ssize_t sel_read_mls(struct file *filp, char __user *buf,
 	char tmpbuf[TMPBUFLEN];
 	ssize_t length;
 
-	length = scnprintf(tmpbuf, TMPBUFLEN, "%d", selinux_mls_enabled);
+	length = scnprintf(tmpbuf, TMPBUFLEN, "%d",
+			   security_mls_enabled());
 	return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
 }
 

security/selinux/ss/context.h

@@ -41,9 +41,6 @@ static inline int mls_context_cpy(struct context *dst, struct context *src)
 {
 	int rc;
 
-	if (!selinux_mls_enabled)
-		return 0;
-
 	dst->range.level[0].sens = src->range.level[0].sens;
 	rc = ebitmap_cpy(&dst->range.level[0].cat, &src->range.level[0].cat);
 	if (rc)
@@ -64,9 +61,6 @@ static inline int mls_context_cpy_low(struct context *dst, struct context *src)
 {
 	int rc;
 
-	if (!selinux_mls_enabled)
-		return 0;
-
 	dst->range.level[0].sens = src->range.level[0].sens;
 	rc = ebitmap_cpy(&dst->range.level[0].cat, &src->range.level[0].cat);
 	if (rc)
@@ -82,9 +76,6 @@ out:
 
 static inline int mls_context_cmp(struct context *c1, struct context *c2)
 {
-	if (!selinux_mls_enabled)
-		return 1;
-
 	return ((c1->range.level[0].sens == c2->range.level[0].sens) &&
 		ebitmap_cmp(&c1->range.level[0].cat, &c2->range.level[0].cat) &&
 		(c1->range.level[1].sens == c2->range.level[1].sens) &&
@@ -93,9 +84,6 @@ static inline int mls_context_cmp(struct context *c1, struct context *c2)
 
 static inline void mls_context_destroy(struct context *c)
 {
-	if (!selinux_mls_enabled)
-		return;
-
 	ebitmap_destroy(&c->range.level[0].cat);
 	ebitmap_destroy(&c->range.level[1].cat);
 	mls_context_init(c);

security/selinux/ss/mls.c

@@ -39,7 +39,7 @@ int mls_compute_context_len(struct context *context)
 	struct ebitmap *e;
 	struct ebitmap_node *node;
 
-	if (!selinux_mls_enabled)
+	if (!policydb.mls_enabled)
 		return 0;
 
 	len = 1; /* for the beginning ":" */
@@ -93,7 +93,7 @@ void mls_sid_to_context(struct context *context,
 	struct ebitmap *e;
 	struct ebitmap_node *node;
 
-	if (!selinux_mls_enabled)
+	if (!policydb.mls_enabled)
 		return;
 
 	scontextp = *scontext;
@@ -200,7 +200,7 @@ int mls_context_isvalid(struct policydb *p, struct context *c)
 {
 	struct user_datum *usrdatum;
 
-	if (!selinux_mls_enabled)
+	if (!p->mls_enabled)
 		return 1;
 
 	if (!mls_range_isvalid(p, &c->range))
@@ -253,7 +253,7 @@ int mls_context_to_sid(struct policydb *pol,
 	struct cat_datum *catdatum, *rngdatum;
 	int l, rc = -EINVAL;
 
-	if (!selinux_mls_enabled) {
+	if (!pol->mls_enabled) {
 		if (def_sid != SECSID_NULL && oldc)
 			*scontext += strlen(*scontext)+1;
 		return 0;
@@ -387,7 +387,7 @@ int mls_from_string(char *str, struct context *context, gfp_t gfp_mask)
 	char *tmpstr, *freestr;
 	int rc;
 
-	if (!selinux_mls_enabled)
+	if (!policydb.mls_enabled)
 		return -EINVAL;
 
 	/* we need freestr because mls_context_to_sid will change
@@ -407,7 +407,7 @@ int mls_from_string(char *str, struct context *context, gfp_t gfp_mask)
 /*
  * Copies the MLS range `range' into `context'.
  */
-static inline int mls_range_set(struct context *context,
+int mls_range_set(struct context *context,
 				struct mls_range *range)
 {
 	int l, rc = 0;
@@ -427,7 +427,7 @@ static inline int mls_range_set(struct context *context,
 int mls_setup_user_range(struct context *fromcon, struct user_datum *user,
 			 struct context *usercon)
 {
-	if (selinux_mls_enabled) {
+	if (policydb.mls_enabled) {
 		struct mls_level *fromcon_sen = &(fromcon->range.level[0]);
 		struct mls_level *fromcon_clr = &(fromcon->range.level[1]);
 		struct mls_level *user_low = &(user->range.level[0]);
@@ -477,7 +477,7 @@ int mls_convert_context(struct policydb *oldp,
 	struct ebitmap_node *node;
 	int l, i;
 
-	if (!selinux_mls_enabled)
+	if (!policydb.mls_enabled)
 		return 0;
 
 	for (l = 0; l < 2; l++) {
@@ -516,7 +516,7 @@ int mls_compute_sid(struct context *scontext,
 	struct range_trans rtr;
 	struct mls_range *r;
 
-	if (!selinux_mls_enabled)
+	if (!policydb.mls_enabled)
 		return 0;
 
 	switch (specified) {
@@ -559,7 +559,7 @@ int mls_compute_sid(struct context *scontext,
 void mls_export_netlbl_lvl(struct context *context,
 			   struct netlbl_lsm_secattr *secattr)
 {
-	if (!selinux_mls_enabled)
+	if (!policydb.mls_enabled)
 		return;
 
 	secattr->attr.mls.lvl = context->range.level[0].sens - 1;
@@ -579,7 +579,7 @@ void mls_export_netlbl_lvl(struct context *context,
 void mls_import_netlbl_lvl(struct context *context,
 			   struct netlbl_lsm_secattr *secattr)
 {
-	if (!selinux_mls_enabled)
+	if (!policydb.mls_enabled)
 		return;
 
 	context->range.level[0].sens = secattr->attr.mls.lvl + 1;
@@ -601,7 +601,7 @@ int mls_export_netlbl_cat(struct context *context,
 {
 	int rc;
 
-	if (!selinux_mls_enabled)
+	if (!policydb.mls_enabled)
 		return 0;
 
 	rc = ebitmap_netlbl_export(&context->range.level[0].cat,
@@ -629,7 +629,7 @@ int mls_import_netlbl_cat(struct context *context,
 {
 	int rc;
 
-	if (!selinux_mls_enabled)
+	if (!policydb.mls_enabled)
 		return 0;
 
 	rc = ebitmap_netlbl_import(&context->range.level[0].cat,

security/selinux/ss/mls.h

@@ -39,6 +39,8 @@ int mls_context_to_sid(struct policydb *p,
 
 int mls_from_string(char *str, struct context *context, gfp_t gfp_mask);
 
+int mls_range_set(struct context *context, struct mls_range *range);
+
 int mls_convert_context(struct policydb *oldp,
 			struct policydb *newp,
 			struct context *context);

security/selinux/ss/mls_types.h

@@ -15,6 +15,7 @@
 #define _SS_MLS_TYPES_H_
 
 #include "security.h"
+#include "ebitmap.h"
 
 struct mls_level {
 	u32 sens;		/* sensitivity */
@@ -27,18 +28,12 @@ struct mls_range {
 
 static inline int mls_level_eq(struct mls_level *l1, struct mls_level *l2)
 {
-	if (!selinux_mls_enabled)
-		return 1;
-
 	return ((l1->sens == l2->sens) &&
 		ebitmap_cmp(&l1->cat, &l2->cat));
 }
 
 static inline int mls_level_dom(struct mls_level *l1, struct mls_level *l2)
 {
-	if (!selinux_mls_enabled)
-		return 1;
-
 	return ((l1->sens >= l2->sens) &&
 		ebitmap_contains(&l1->cat, &l2->cat));
 }

security/selinux/ss/policydb.c

@@ -52,8 +52,6 @@ static char *symtab_name[SYM_NUM] = {
 };
 #endif
 
-int selinux_mls_enabled;
-
 static unsigned int symtab_sizes[SYM_NUM] = {
 	2,
 	32,
@@ -455,7 +453,7 @@ static int policydb_index_others(struct policydb *p)
 
 	printk(KERN_DEBUG "SELinux:  %d users, %d roles, %d types, %d bools",
 	       p->p_users.nprim, p->p_roles.nprim, p->p_types.nprim, p->p_bools.nprim);
-	if (selinux_mls_enabled)
+	if (p->mls_enabled)
 		printk(", %d sens, %d cats", p->p_levels.nprim,
 		       p->p_cats.nprim);
 	printk("\n");
@@ -1717,14 +1715,12 @@ int policydb_read(struct policydb *p, void *fp)
 	int i, j, rc;
 	__le32 buf[4];
 	u32 nodebuf[8];
-	u32 len, len2, config, nprim, nel, nel2;
+	u32 len, len2, nprim, nel, nel2;
 	char *policydb_str;
 	struct policydb_compat_info *info;
 	struct range_trans *rt;
 	struct mls_range *r;
 
-	config = 0;
-
 	rc = policydb_init(p);
 	if (rc)
 		goto out;
@@ -1772,7 +1768,7 @@ int policydb_read(struct policydb *p, void *fp)
 	kfree(policydb_str);
 	policydb_str = NULL;
 
-	/* Read the version, config, and table sizes. */
+	/* Read the version and table sizes. */
 	rc = next_entry(buf, fp, sizeof(u32)*4);
 	if (rc < 0)
 		goto bad;
@@ -1787,13 +1783,7 @@ int policydb_read(struct policydb *p, void *fp)
 	}
 
 	if ((le32_to_cpu(buf[1]) & POLICYDB_CONFIG_MLS)) {
-		if (ss_initialized && !selinux_mls_enabled) {
-			printk(KERN_ERR "SELinux: Cannot switch between non-MLS"
-				" and MLS policies\n");
-			goto bad;
-		}
-		selinux_mls_enabled = 1;
-		config |= POLICYDB_CONFIG_MLS;
+		p->mls_enabled = 1;
 
 		if (p->policyvers < POLICYDB_VERSION_MLS) {
 			printk(KERN_ERR "SELinux: security policydb version %d "
@@ -1801,12 +1791,6 @@ int policydb_read(struct policydb *p, void *fp)
 				p->policyvers);
 			goto bad;
 		}
-	} else {
-		if (ss_initialized && selinux_mls_enabled) {
-			printk(KERN_ERR "SELinux: Cannot switch between MLS and"
-				" non-MLS policies\n");
-			goto bad;
-		}
 	}
 	p->reject_unknown = !!(le32_to_cpu(buf[1]) & REJECT_UNKNOWN);
 	p->allow_unknown = !!(le32_to_cpu(buf[1]) & ALLOW_UNKNOWN);

security/selinux/ss/policydb.h

@@ -27,6 +27,8 @@
 #include "symtab.h"
 #include "avtab.h"
 #include "sidtab.h"
+#include "ebitmap.h"
+#include "mls_types.h"
 #include "context.h"
 #include "constraint.h"
 
@@ -185,6 +187,8 @@ struct genfs {
 
 /* The policy database */
 struct policydb {
+	int mls_enabled;
+
 	/* symbol tables */
 	struct symtab symtab[SYM_NUM];
 #define p_commons symtab[SYM_COMMONS]

security/selinux/ss/services.c

@@ -26,6 +26,10 @@
  *
  *  Added support for bounds domain and audit messaged on masked permissions
  *
+ * Updated: Guido Trentalancia <guido@trentalancia.com>
+ *
+ *  Added support for runtime switching of the policy type
+ *
  * Copyright (C) 2008, 2009 NEC Corporation
  * Copyright (C) 2006, 2007 Hewlett-Packard Development Company, L.P.
  * Copyright (C) 2004-2006 Trusted Computer Solutions, Inc.
@@ -232,6 +236,10 @@ static void map_decision(u16 tclass, struct av_decision *avd,
 	}
 }
 
+int security_mls_enabled(void)
+{
+	return policydb.mls_enabled;
+}
 
 /*
  * Return the boolean value of a constraint expression
@@ -1550,6 +1558,8 @@ static int convert_context(u32 key,
 {
 	struct convert_context_args *args;
 	struct context oldc;
+	struct ocontext *oc;
+	struct mls_range *range;
 	struct role_datum *role;
 	struct type_datum *typdatum;
 	struct user_datum *usrdatum;
@@ -1620,9 +1630,39 @@ static int convert_context(u32 key,
 		goto bad;
 	c->type = typdatum->value;
 
+	/* Convert the MLS fields if dealing with MLS policies */
+	if (args->oldp->mls_enabled && args->newp->mls_enabled) {
 		rc = mls_convert_context(args->oldp, args->newp, c);
 		if (rc)
 			goto bad;
+	} else if (args->oldp->mls_enabled && !args->newp->mls_enabled) {
+		/*
+		 * Switching between MLS and non-MLS policy:
+		 * free any storage used by the MLS fields in the
+		 * context for all existing entries in the sidtab.
+		 */
+		mls_context_destroy(c);
+	} else if (!args->oldp->mls_enabled && args->newp->mls_enabled) {
+		/*
+		 * Switching between non-MLS and MLS policy:
+		 * ensure that the MLS fields of the context for all
+		 * existing entries in the sidtab are filled in with a
+		 * suitable default value, likely taken from one of the
+		 * initial SIDs.
+		 */
+		oc = args->newp->ocontexts[OCON_ISID];
+		while (oc && oc->sid[0] != SECINITSID_UNLABELED)
+			oc = oc->next;
+		if (!oc) {
+			printk(KERN_ERR "SELinux:  unable to look up"
+				" the initial SIDs list\n");
+			goto bad;
+		}
+		range = &oc->context[0].range;
+		rc = mls_range_set(c, range);
+		if (rc)
+			goto bad;
+	}
 
 	/* Check the validity of the new context. */
 	if (!policydb_context_isvalid(args->newp, c)) {
@@ -1718,6 +1758,12 @@ int security_load_policy(void *data, size_t len)
 	if (policydb_read(&newpolicydb, fp))
 		return -EINVAL;
 
+	/* If switching between different policy types, log MLS status */
+	if (policydb.mls_enabled && !newpolicydb.mls_enabled)
+		printk(KERN_INFO "SELinux: Disabling MLS support...\n");
+	else if (!policydb.mls_enabled && newpolicydb.mls_enabled)
+		printk(KERN_INFO "SELinux: Enabling MLS support...\n");
+
 	rc = policydb_load_isids(&newpolicydb, &newsidtab);
 	if (rc) {
 		printk(KERN_ERR "SELinux:  unable to load the initial SIDs\n");
@@ -1749,8 +1795,12 @@ int security_load_policy(void *data, size_t len)
 	args.oldp = &policydb;
 	args.newp = &newpolicydb;
 	rc = sidtab_map(&newsidtab, convert_context, &args);
-	if (rc)
+	if (rc) {
+		printk(KERN_ERR "SELinux:  unable to convert the internal"
+			" representation of contexts in the new SID"
+			" table\n");
 		goto err;
+	}
 
 	/* Save the old policydb and SID table to free later. */
 	memcpy(&oldpolicydb, &policydb, sizeof policydb);
@@ -2346,7 +2396,7 @@ int security_sid_mls_copy(u32 sid, u32 mls_sid, u32 *new_sid)
 	u32 len;
 	int rc = 0;
 
-	if (!ss_initialized || !selinux_mls_enabled) {
+	if (!ss_initialized || !policydb.mls_enabled) {
 		*new_sid = sid;
 		goto out;
 	}
@@ -2447,7 +2497,7 @@ int security_net_peersid_resolve(u32 nlbl_sid, u32 nlbl_type,
 	/* we don't need to check ss_initialized here since the only way both
 	 * nlbl_sid and xfrm_sid are not equal to SECSID_NULL would be if the
 	 * security server was initialized and ss_initialized was true */
-	if (!selinux_mls_enabled) {
+	if (!policydb.mls_enabled) {
 		*peer_sid = SECSID_NULL;
 		return 0;
 	}