Merge branch 'smack-for-4.4' of https://github.com/cschaufler/smack-next into next

Documentation/security/Smack.txt

···
 	the access permitted if it wouldn't be otherwise. Note that this
 	is dangerous and can ruin the proper labeling of your system.
 	It should never be used in production.
+relabel-self
+	This interface contains a list of labels to which the process can
+	transition to, by writing to /proc/self/attr/current.
+	Normally a process can change its own label to any legal value, but only
+	if it has CAP_MAC_ADMIN. This interface allows a process without
+	CAP_MAC_ADMIN to relabel itself to one of labels from predefined list.
+	A process without CAP_MAC_ADMIN can change its label only once. When it
+	does, this list will be cleared.
+	The values are set by writing the desired labels, separated
+	by spaces, to the file or cleared by writing "-" to the file.
 
 If you are using the smackload utility
 you can add access rules in /etc/smack/accesses. They take the form:

security/smack/smack.h

···
 	struct smack_known	*smk_forked;	/* label when forked */
 	struct list_head	smk_rules;	/* per task access rules */
 	struct mutex		smk_rules_lock;	/* lock for the rules */
+	struct list_head	smk_relabel;	/* transit allowed labels */
 };
 
 #define	SMK_INODE_INSTANT	0x01	/* inode is instantiated */
···
 };
 #endif /* SMACK_IPV6_PORT_LABELING */
 
-struct smack_onlycap {
+struct smack_known_list_elem {
 	struct list_head	list;
 	struct smack_known	*smk_label;
 };
···
 void smk_insert_entry(struct smack_known *skp);
 struct smack_known *smk_find_entry(const char *);
 int smack_privileged(int cap);
+void smk_destroy_label_list(struct list_head *list);
 
 /*
  * Shared data.

security/smack/smack_access.c

···
 int smack_privileged(int cap)
 {
 	struct smack_known *skp = smk_of_current();
-	struct smack_onlycap *sop;
+	struct smack_known_list_elem *sklep;
 
 	/*
 	 * All kernel tasks are privileged
···
 		return 1;
 	}
 
-	list_for_each_entry_rcu(sop, &smack_onlycap_list, list) {
-		if (sop->smk_label == skp) {
+	list_for_each_entry_rcu(sklep, &smack_onlycap_list, list) {
+		if (sklep->smk_label == skp) {
 			rcu_read_unlock();
 			return 1;
 		}

security/smack/smack_lsm.c

···
 #define SMK_SENDING	2
 
 #ifdef SMACK_IPV6_PORT_LABELING
-LIST_HEAD(smk_ipv6_port_list);
+static LIST_HEAD(smk_ipv6_port_list);
 #endif
 static struct kmem_cache *smack_inode_cache;
 int smack_enabled;
···
 	tsp->smk_task = task;
 	tsp->smk_forked = forked;
 	INIT_LIST_HEAD(&tsp->smk_rules);
+	INIT_LIST_HEAD(&tsp->smk_relabel);
 	mutex_init(&tsp->smk_rules_lock);
 
 	return tsp;
···
 		list_add_rcu(&nrp->list, nhead);
 	}
 	return rc;
+}
+
+/**
+ * smk_copy_relabel - copy smk_relabel labels list
+ * @nhead: new rules header pointer
+ * @ohead: old rules header pointer
+ * @gfp: type of the memory for the allocation
+ *
+ * Returns 0 on success, -ENOMEM on error
+ */
+static int smk_copy_relabel(struct list_head *nhead, struct list_head *ohead,
+				gfp_t gfp)
+{
+	struct smack_known_list_elem *nklep;
+	struct smack_known_list_elem *oklep;
+
+	INIT_LIST_HEAD(nhead);
+
+	list_for_each_entry(oklep, ohead, list) {
+		nklep = kzalloc(sizeof(struct smack_known_list_elem), gfp);
+		if (nklep == NULL) {
+			smk_destroy_label_list(nhead);
+			return -ENOMEM;
+		}
+		nklep->smk_label = oklep->smk_label;
+		list_add(&nklep->list, nhead);
+	}
+
+	return 0;
 }
 
 /**
···
 		return;
 	cred->security = NULL;
 
+	smk_destroy_label_list(&tsp->smk_relabel);
+
 	list_for_each_safe(l, n, &tsp->smk_rules) {
 		rp = list_entry(l, struct smack_rule, list);
 		list_del(&rp->list);
···
 		return -ENOMEM;
 
 	rc = smk_copy_rules(&new_tsp->smk_rules, &old_tsp->smk_rules, gfp);
+	if (rc != 0)
+		return rc;
+
+	rc = smk_copy_relabel(&new_tsp->smk_relabel, &old_tsp->smk_relabel,
+				gfp);
 	if (rc != 0)
 		return rc;
 
···
 			 */
 			isp->smk_inode = smk_of_current();
 			break;
+		case PIPEFS_MAGIC:
+			isp->smk_inode = smk_of_current();
+			break;
 		default:
 			isp->smk_inode = sbsp->smk_root;
 			break;
···
 static int smack_setprocattr(struct task_struct *p, char *name,
 			     void *value, size_t size)
 {
-	struct task_smack *tsp;
+	struct task_smack *tsp = current_security();
 	struct cred *new;
 	struct smack_known *skp;
+	struct smack_known_list_elem *sklep;
+	int rc;
 
 	/*
 	 * Changing another process' Smack value is too dangerous
···
 	if (p != current)
 		return -EPERM;
 
-	if (!smack_privileged(CAP_MAC_ADMIN))
+	if (!smack_privileged(CAP_MAC_ADMIN) && list_empty(&tsp->smk_relabel))
 		return -EPERM;
 
 	if (value == NULL || size == 0 || size >= SMK_LONGLABEL)
···
 	if (skp == &smack_known_web)
 		return -EPERM;
 
+	if (!smack_privileged(CAP_MAC_ADMIN)) {
+		rc = -EPERM;
+		list_for_each_entry(sklep, &tsp->smk_relabel, list)
+			if (sklep->smk_label == skp) {
+				rc = 0;
+				break;
+			}
+		if (rc)
+			return rc;
+	}
+
 	new = prepare_creds();
 	if (new == NULL)
 		return -ENOMEM;
 
 	tsp = new->security;
 	tsp->smk_task = skp;
+	/*
+	 * process can change its label only once
+	 */
+	smk_destroy_label_list(&tsp->smk_relabel);
 
 	commit_creds(new);
 	return size;
···
 	if (!security_module_enable("smack"))
 		return 0;
 
-	smack_enabled = 1;
-
 	smack_inode_cache = KMEM_CACHE(inode_smack, 0);
 	if (!smack_inode_cache)
 		return -ENOMEM;
···
 		kmem_cache_destroy(smack_inode_cache);
 		return -ENOMEM;
 	}
+
+	smack_enabled = 1;
 
 	pr_info("Smack:  Initializing.\n");
 #ifdef CONFIG_SECURITY_SMACK_NETFILTER

security/smack/smackfs.c

···
 #if IS_ENABLED(CONFIG_IPV6)
 	SMK_NET6ADDR	= 23,	/* single label IPv6 hosts */
 #endif /* CONFIG_IPV6 */
+	SMK_RELABEL_SELF = 24, /* relabel possible without CAP_MAC_ADMIN */
 };
 
 /*
···
 	 */
 	if (smack[0] != '-') {
 		skp = smk_import_entry(smack, 0);
-		if (skp == NULL) {
-			rc = -EINVAL;
+		if (IS_ERR(skp)) {
+			rc = PTR_ERR(skp);
 			goto free_out;
 		}
 	} else {
···
 static int onlycap_seq_show(struct seq_file *s, void *v)
 {
 	struct list_head *list = v;
-	struct smack_onlycap *sop =
-		list_entry_rcu(list, struct smack_onlycap, list);
+	struct smack_known_list_elem *sklep =
+		list_entry_rcu(list, struct smack_known_list_elem, list);
 
-	seq_puts(s, sop->smk_label->smk_known);
+	seq_puts(s, sklep->smk_label->smk_known);
 	seq_putc(s, ' ');
 
 	return 0;
···
 }
 
 /**
+ * smk_parse_label_list - parse list of Smack labels, separated by spaces
+ *
+ * @data: the string to parse
+ * @private: destination list
+ *
+ * Returns zero on success or error code, as appropriate
+ */
+static int smk_parse_label_list(char *data, struct list_head *list)
+{
+	char *tok;
+	struct smack_known *skp;
+	struct smack_known_list_elem *sklep;
+
+	while ((tok = strsep(&data, " ")) != NULL) {
+		if (!*tok)
+			continue;
+
+		skp = smk_import_entry(tok, 0);
+		if (IS_ERR(skp))
+			return PTR_ERR(skp);
+
+		sklep = kzalloc(sizeof(*sklep), GFP_KERNEL);
+		if (sklep == NULL)
+			return -ENOMEM;
+
+		sklep->smk_label = skp;
+		list_add(&sklep->list, list);
+	}
+
+	return 0;
+}
+
+/**
+ * smk_destroy_label_list - destroy a list of smack_known_list_elem
+ * @head: header pointer of the list to destroy
+ */
+void smk_destroy_label_list(struct list_head *list)
+{
+	struct smack_known_list_elem *sklep;
+	struct smack_known_list_elem *sklep2;
+
+	list_for_each_entry_safe(sklep, sklep2, list, list)
+		kfree(sklep);
+
+	INIT_LIST_HEAD(list);
+}
+
+/**
  * smk_write_onlycap - write() for smackfs/onlycap
  * @file: file pointer, not actually used
  * @buf: where to get the data from
···
 				 size_t count, loff_t *ppos)
 {
 	char *data;
-	char *data_parse;
-	char *tok;
-	struct smack_known *skp;
-	struct smack_onlycap *sop;
-	struct smack_onlycap *sop2;
 	LIST_HEAD(list_tmp);
-	int rc = count;
+	int rc;
 
 	if (!smack_privileged(CAP_MAC_ADMIN))
 		return -EPERM;
···
 		return -EFAULT;
 	}
 
-	data_parse = data;
-	while ((tok = strsep(&data_parse, " ")) != NULL) {
-		if (!*tok)
-			continue;
-
-		skp = smk_import_entry(tok, 0);
-		if (IS_ERR(skp)) {
-			rc = PTR_ERR(skp);
-			break;
-		}
-
-		sop = kzalloc(sizeof(*sop), GFP_KERNEL);
-		if (sop == NULL) {
-			rc = -ENOMEM;
-			break;
-		}
-
-		sop->smk_label = skp;
-		list_add_rcu(&sop->list, &list_tmp);
-	}
+	rc = smk_parse_label_list(data, &list_tmp);
 	kfree(data);
 
 	/*
···
 	 * But do so only on invalid label, not on system errors.
 	 * The invalid label must be first to count as clearing attempt.
 	 */
-	if (rc == -EINVAL && list_empty(&list_tmp))
-		rc = count;
-
-	if (rc >= 0) {
+	if (!rc || (rc == -EINVAL && list_empty(&list_tmp))) {
 		mutex_lock(&smack_onlycap_lock);
 		smk_list_swap_rcu(&smack_onlycap_list, &list_tmp);
 		mutex_unlock(&smack_onlycap_lock);
+		rc = count;
 	}
 
-	list_for_each_entry_safe(sop, sop2, &list_tmp, list)
-		kfree(sop);
+	smk_destroy_label_list(&list_tmp);
 
 	return rc;
 }
···
 	.llseek		= default_llseek,
 };
 
+/*
+ * Seq_file read operations for /smack/relabel-self
+ */
+
+static void *relabel_self_seq_start(struct seq_file *s, loff_t *pos)
+{
+	struct task_smack *tsp = current_security();
+
+	return smk_seq_start(s, pos, &tsp->smk_relabel);
+}
+
+static void *relabel_self_seq_next(struct seq_file *s, void *v, loff_t *pos)
+{
+	struct task_smack *tsp = current_security();
+
+	return smk_seq_next(s, v, pos, &tsp->smk_relabel);
+}
+
+static int relabel_self_seq_show(struct seq_file *s, void *v)
+{
+	struct list_head *list = v;
+	struct smack_known_list_elem *sklep =
+		list_entry(list, struct smack_known_list_elem, list);
+
+	seq_puts(s, sklep->smk_label->smk_known);
+	seq_putc(s, ' ');
+
+	return 0;
+}
+
+static const struct seq_operations relabel_self_seq_ops = {
+	.start = relabel_self_seq_start,
+	.next  = relabel_self_seq_next,
+	.show  = relabel_self_seq_show,
+	.stop  = smk_seq_stop,
+};
+
+/**
+ * smk_open_relabel_self - open() for /smack/relabel-self
+ * @inode: inode structure representing file
+ * @file: "relabel-self" file pointer
+ *
+ * Connect our relabel_self_seq_* operations with /smack/relabel-self
+ * file_operations
+ */
+static int smk_open_relabel_self(struct inode *inode, struct file *file)
+{
+	return seq_open(file, &relabel_self_seq_ops);
+}
+
+/**
+ * smk_write_relabel_self - write() for /smack/relabel-self
+ * @file: file pointer, not actually used
+ * @buf: where to get the data from
+ * @count: bytes sent
+ * @ppos: where to start - must be 0
+ *
+ */
+static ssize_t smk_write_relabel_self(struct file *file, const char __user *buf,
+				size_t count, loff_t *ppos)
+{
+	struct task_smack *tsp = current_security();
+	char *data;
+	int rc;
+	LIST_HEAD(list_tmp);
+
+	/*
+	 * Must have privilege.
+	 */
+	if (!smack_privileged(CAP_MAC_ADMIN))
+		return -EPERM;
+
+	/*
+	 * Enough data must be present.
+	 */
+	if (*ppos != 0)
+		return -EINVAL;
+
+	data = kzalloc(count + 1, GFP_KERNEL);
+	if (data == NULL)
+		return -ENOMEM;
+
+	if (copy_from_user(data, buf, count) != 0) {
+		kfree(data);
+		return -EFAULT;
+	}
+
+	rc = smk_parse_label_list(data, &list_tmp);
+	kfree(data);
+
+	if (!rc || (rc == -EINVAL && list_empty(&list_tmp))) {
+		smk_destroy_label_list(&tsp->smk_relabel);
+		list_splice(&list_tmp, &tsp->smk_relabel);
+		return count;
+	}
+
+	smk_destroy_label_list(&list_tmp);
+	return rc;
+}
+
+static const struct file_operations smk_relabel_self_ops = {
+	.open		= smk_open_relabel_self,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.write		= smk_write_relabel_self,
+	.release	= seq_release,
+};
 
 /**
  * smk_read_ptrace - read() for /smack/ptrace
···
 		[SMK_NET6ADDR] = {
 			"ipv6host", &smk_net6addr_ops, S_IRUGO|S_IWUSR},
 #endif /* CONFIG_IPV6 */
+		[SMK_RELABEL_SELF] = {
+			"relabel-self", &smk_relabel_self_ops,
+				S_IRUGO|S_IWUGO},
 		/* last one */
 			{""}
 	};
···
 	int err;
 	int rc;
 
-	if (!security_module_enable("smack"))
+	if (smack_enabled == 0)
 		return 0;
 
 	err = smk_init_sysfs();