selinux: Add a cache for quicker retreival of PKey SIDs

It is likely that the SID for the same PKey will be requested many
times. To reduce the time to modify QPs and process MADs use a cache to
store PKey SIDs.

This code is heavily based on the "netif" and "netport" concept
originally developed by James Morris <[e-mail]> and Paul Moore
<[e-mail]> (see security/selinux/netif.c and
security/selinux/netport.c for more information)

Signed-off-by: Daniel Jurgens <[e-mail]>
Acked-by: Doug Ledford <[e-mail]>
Signed-off-by: Paul Moore <[e-mail]>

security/selinux/Makefile

···
 obj-$(CONFIG_SECURITY_SELINUX) := selinux.o
 
 selinux-y := avc.o hooks.o selinuxfs.o netlink.o nlmsgtab.o netif.o \
-	     netnode.o netport.o exports.o \
+	     netnode.o netport.o ibpkey.o exports.o \
 	     ss/ebitmap.o ss/hashtab.o ss/symtab.o ss/sidtab.o ss/avtab.o \
 	     ss/policydb.o ss/services.o ss/conditional.o ss/mls.o ss/status.o
 

security/selinux/hooks.c

···
 #include "netif.h"
 #include "netnode.h"
 #include "netport.h"
+#include "ibpkey.h"
 #include "xfrm.h"
 #include "netlabel.h"
 #include "audit.h"
···
 
 static int selinux_lsm_notifier_avc_callback(u32 event)
 {
-	if (event == AVC_CALLBACK_RESET)
+	if (event == AVC_CALLBACK_RESET) {
+		sel_ib_pkey_flush();
 		call_lsm_notifier(LSM_POLICY_CHANGE, NULL);
+	}
 
 	return 0;
 }
···
 	struct ib_security_struct *sec = ib_sec;
 	struct lsm_ibpkey_audit ibpkey;
 
-	err = security_ib_pkey_sid(subnet_prefix, pkey_val, &sid);
+	err = sel_ib_pkey_sid(subnet_prefix, pkey_val, &sid);
 	if (err)
 		return err;
 

security/selinux/ibpkey.c

···
+/*
+ * Pkey table
+ *
+ * SELinux must keep a mapping of Infinband PKEYs to labels/SIDs.  This
+ * mapping is maintained as part of the normal policy but a fast cache is
+ * needed to reduce the lookup overhead.
+ *
+ * This code is heavily based on the "netif" and "netport" concept originally
+ * developed by
+ * James Morris <[e-mail]> and
+ * Paul Moore <[e-mail]>
+ *   (see security/selinux/netif.c and security/selinux/netport.c for more
+ *   information)
+ *
+ */
+
+/*
+ * (c) Mellanox Technologies, 2016
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/types.h>
+#include <linux/rcupdate.h>
+#include <linux/list.h>
+#include <linux/spinlock.h>
+
+#include "ibpkey.h"
+#include "objsec.h"
+
+#define SEL_PKEY_HASH_SIZE       256
+#define SEL_PKEY_HASH_BKT_LIMIT   16
+
+struct sel_ib_pkey_bkt {
+	int size;
+	struct list_head list;
+};
+
+struct sel_ib_pkey {
+	struct pkey_security_struct psec;
+	struct list_head list;
+	struct rcu_head rcu;
+};
+
+static LIST_HEAD(sel_ib_pkey_list);
+static DEFINE_SPINLOCK(sel_ib_pkey_lock);
+static struct sel_ib_pkey_bkt sel_ib_pkey_hash[SEL_PKEY_HASH_SIZE];
+
+/**
+ * sel_ib_pkey_hashfn - Hashing function for the pkey table
+ * @pkey: pkey number
+ *
+ * Description:
+ * This is the hashing function for the pkey table, it returns the bucket
+ * number for the given pkey.
+ *
+ */
+static unsigned int sel_ib_pkey_hashfn(u16 pkey)
+{
+	return (pkey & (SEL_PKEY_HASH_SIZE - 1));
+}
+
+/**
+ * sel_ib_pkey_find - Search for a pkey record
+ * @subnet_prefix: subnet_prefix
+ * @pkey_num: pkey_num
+ *
+ * Description:
+ * Search the pkey table and return the matching record.  If an entry
+ * can not be found in the table return NULL.
+ *
+ */
+static struct sel_ib_pkey *sel_ib_pkey_find(u64 subnet_prefix, u16 pkey_num)
+{
+	unsigned int idx;
+	struct sel_ib_pkey *pkey;
+
+	idx = sel_ib_pkey_hashfn(pkey_num);
+	list_for_each_entry_rcu(pkey, &sel_ib_pkey_hash[idx].list, list) {
+		if (pkey->psec.pkey == pkey_num &&
+		    pkey->psec.subnet_prefix == subnet_prefix)
+			return pkey;
+	}
+
+	return NULL;
+}
+
+/**
+ * sel_ib_pkey_insert - Insert a new pkey into the table
+ * @pkey: the new pkey record
+ *
+ * Description:
+ * Add a new pkey record to the hash table.
+ *
+ */
+static void sel_ib_pkey_insert(struct sel_ib_pkey *pkey)
+{
+	unsigned int idx;
+
+	/* we need to impose a limit on the growth of the hash table so check
+	 * this bucket to make sure it is within the specified bounds
+	 */
+	idx = sel_ib_pkey_hashfn(pkey->psec.pkey);
+	list_add_rcu(&pkey->list, &sel_ib_pkey_hash[idx].list);
+	if (sel_ib_pkey_hash[idx].size == SEL_PKEY_HASH_BKT_LIMIT) {
+		struct sel_ib_pkey *tail;
+
+		tail = list_entry(
+			rcu_dereference_protected(
+				sel_ib_pkey_hash[idx].list.prev,
+				lockdep_is_held(&sel_ib_pkey_lock)),
+			struct sel_ib_pkey, list);
+		list_del_rcu(&tail->list);
+		kfree_rcu(tail, rcu);
+	} else {
+		sel_ib_pkey_hash[idx].size++;
+	}
+}
+
+/**
+ * sel_ib_pkey_sid_slow - Lookup the SID of a pkey using the policy
+ * @subnet_prefix: subnet prefix
+ * @pkey_num: pkey number
+ * @sid: pkey SID
+ *
+ * Description:
+ * This function determines the SID of a pkey by querying the security
+ * policy.  The result is added to the pkey table to speedup future
+ * queries.  Returns zero on success, negative values on failure.
+ *
+ */
+static int sel_ib_pkey_sid_slow(u64 subnet_prefix, u16 pkey_num, u32 *sid)
+{
+	int ret;
+	struct sel_ib_pkey *pkey;
+	struct sel_ib_pkey *new = NULL;
+	unsigned long flags;
+
+	spin_lock_irqsave(&sel_ib_pkey_lock, flags);
+	pkey = sel_ib_pkey_find(subnet_prefix, pkey_num);
+	if (pkey) {
+		*sid = pkey->psec.sid;
+		spin_unlock_irqrestore(&sel_ib_pkey_lock, flags);
+		return 0;
+	}
+
+	ret = security_ib_pkey_sid(subnet_prefix, pkey_num, sid);
+	if (ret)
+		goto out;
+
+	/* If this memory allocation fails still return 0. The SID
+	 * is valid, it just won't be added to the cache.
+	 */
+	new = kzalloc(sizeof(*new), GFP_ATOMIC);
+	if (!new)
+		goto out;
+
+	new->psec.subnet_prefix = subnet_prefix;
+	new->psec.pkey = pkey_num;
+	new->psec.sid = *sid;
+	sel_ib_pkey_insert(new);
+
+out:
+	spin_unlock_irqrestore(&sel_ib_pkey_lock, flags);
+	return ret;
+}
+
+/**
+ * sel_ib_pkey_sid - Lookup the SID of a PKEY
+ * @subnet_prefix: subnet_prefix
+ * @pkey_num: pkey number
+ * @sid: pkey SID
+ *
+ * Description:
+ * This function determines the SID of a PKEY using the fastest method
+ * possible.  First the pkey table is queried, but if an entry can't be found
+ * then the policy is queried and the result is added to the table to speedup
+ * future queries.  Returns zero on success, negative values on failure.
+ *
+ */
+int sel_ib_pkey_sid(u64 subnet_prefix, u16 pkey_num, u32 *sid)
+{
+	struct sel_ib_pkey *pkey;
+
+	rcu_read_lock();
+	pkey = sel_ib_pkey_find(subnet_prefix, pkey_num);
+	if (pkey) {
+		*sid = pkey->psec.sid;
+		rcu_read_unlock();
+		return 0;
+	}
+	rcu_read_unlock();
+
+	return sel_ib_pkey_sid_slow(subnet_prefix, pkey_num, sid);
+}
+
+/**
+ * sel_ib_pkey_flush - Flush the entire pkey table
+ *
+ * Description:
+ * Remove all entries from the pkey table
+ *
+ */
+void sel_ib_pkey_flush(void)
+{
+	unsigned int idx;
+	struct sel_ib_pkey *pkey, *pkey_tmp;
+	unsigned long flags;
+
+	spin_lock_irqsave(&sel_ib_pkey_lock, flags);
+	for (idx = 0; idx < SEL_PKEY_HASH_SIZE; idx++) {
+		list_for_each_entry_safe(pkey, pkey_tmp,
+					 &sel_ib_pkey_hash[idx].list, list) {
+			list_del_rcu(&pkey->list);
+			kfree_rcu(pkey, rcu);
+		}
+		sel_ib_pkey_hash[idx].size = 0;
+	}
+	spin_unlock_irqrestore(&sel_ib_pkey_lock, flags);
+}
+
+static __init int sel_ib_pkey_init(void)
+{
+	int iter;
+
+	if (!selinux_enabled)
+		return 0;
+
+	for (iter = 0; iter < SEL_PKEY_HASH_SIZE; iter++) {
+		INIT_LIST_HEAD(&sel_ib_pkey_hash[iter].list);
+		sel_ib_pkey_hash[iter].size = 0;
+	}
+
+	return 0;
+}
+
+subsys_initcall(sel_ib_pkey_init);

security/selinux/include/ibpkey.h

···
+/*
+ * pkey table
+ *
+ * SELinux must keep a mapping of pkeys to labels/SIDs.  This
+ * mapping is maintained as part of the normal policy but a fast cache is
+ * needed to reduce the lookup overhead.
+ *
+ */
+
+/*
+ * (c) Mellanox Technologies, 2016
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef _SELINUX_IB_PKEY_H
+#define _SELINUX_IB_PKEY_H
+
+void sel_ib_pkey_flush(void);
+
+int sel_ib_pkey_sid(u64 subnet_prefix, u16 pkey, u32 *sid);
+
+#endif

security/selinux/include/objsec.h

···
 	u32 sid;        /* SID of the queue pair or MAD agent */
 };
 
+struct pkey_security_struct {
+	u64	subnet_prefix; /* Port subnet prefix */
+	u16	pkey;	/* PKey number */
+	u32	sid;	/* SID of pkey */
+};
+
 extern unsigned int selinux_checkreqprot;
 
 #endif /* _SELINUX_OBJSEC_H_ */