NetLabel: SELinux cleanups

This patch does a lot of cleanup in the SELinux NetLabel support code.  A
summary of the changes include:

* Use RCU locking for the NetLabel state variable in the skk_security_struct
  instead of using the inode_security_struct mutex.
* Remove unnecessary parameters in selinux_netlbl_socket_post_create().
* Rename selinux_netlbl_sk_clone_security() to
  selinux_netlbl_sk_security_clone() to better fit the other NetLabel
  sk_security functions.
* Improvements to selinux_netlbl_inode_permission() to help reduce the cost of
  the common case.

Signed-off-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: James Morris <jmorris@namei.org>

4 files changed, 86 insertions, 54 deletions

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 0cf98740ddc6..975c0dfb5a11 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3140,9 +3140,7 @@ static int selinux_socket_post_create(struct socket *sock, int family,
         if (sock->sk) {
                 sksec = sock->sk->sk_security;
                 sksec->sid = isec->sid;
-                err = selinux_netlbl_socket_post_create(sock,
-                                                        family,
-                                                        isec->sid);
+                err = selinux_netlbl_socket_post_create(sock);
         }
 
         return err;
@@ -3661,7 +3659,7 @@ static void selinux_sk_clone_security(const struct sock *sk, struct sock *newsk)
         newssec->sid = ssec->sid;
         newssec->peer_sid = ssec->peer_sid;
 
-        selinux_netlbl_sk_clone_security(ssec, newssec);
+        selinux_netlbl_sk_security_clone(ssec, newssec);
 }
 
 static void selinux_sk_getsecid(struct sock *sk, u32 *secid)
@@ -3730,7 +3728,9 @@ static void selinux_inet_csk_clone(struct sock *newsk,
            So we will wait until sock_graft to do it, by which
            time it will have been created and available. */
 
-        selinux_netlbl_sk_security_init(newsksec, req->rsk_ops->family);
+        /* We don't need to take any sort of lock here as we are the only
+         * thread with access to newsksec */
+        selinux_netlbl_sk_security_reset(newsksec, req->rsk_ops->family);
 }
 
 static void selinux_inet_conn_established(struct sock *sk,
diff --git a/security/selinux/include/objsec.h b/security/selinux/include/objsec.h
index ef2267fea8bd..91b88f0ba20c 100644
--- a/security/selinux/include/objsec.h
+++ b/security/selinux/include/objsec.h
@@ -23,6 +23,7 @@
 #include <linux/fs.h>
 #include <linux/binfmts.h>
 #include <linux/in.h>
+#include <linux/spinlock.h>
 #include "flask.h"
 #include "avc.h"
 
@@ -108,6 +109,7 @@ struct sk_security_struct {
                 NLBL_REQUIRE,
                 NLBL_LABELED,
         } nlbl_state;
+        spinlock_t nlbl_lock;           /* protects nlbl_state */
 #endif
 };
 
diff --git a/security/selinux/include/selinux_netlabel.h b/security/selinux/include/selinux_netlabel.h
index 9de10cc2cef2..57943f4a8f90 100644
--- a/security/selinux/include/selinux_netlabel.h
+++ b/security/selinux/include/selinux_netlabel.h
@@ -38,9 +38,7 @@
 
 #ifdef CONFIG_NETLABEL
 void selinux_netlbl_cache_invalidate(void);
-int selinux_netlbl_socket_post_create(struct socket *sock,
-                                      int sock_family,
-                                      u32 sid);
+int selinux_netlbl_socket_post_create(struct socket *sock);
 void selinux_netlbl_sock_graft(struct sock *sk, struct socket *sock);
 u32 selinux_netlbl_inet_conn_request(struct sk_buff *skb, u32 sock_sid);
 int selinux_netlbl_sock_rcv_skb(struct sk_security_struct *sksec,
@@ -48,9 +46,11 @@ int selinux_netlbl_sock_rcv_skb(struct sk_security_struct *sksec,
                                 struct avc_audit_data *ad);
 u32 selinux_netlbl_socket_getpeersec_stream(struct socket *sock);
 u32 selinux_netlbl_socket_getpeersec_dgram(struct sk_buff *skb);
+void selinux_netlbl_sk_security_reset(struct sk_security_struct *ssec,
+                                      int family);
 void selinux_netlbl_sk_security_init(struct sk_security_struct *ssec,
                                      int family);
-void selinux_netlbl_sk_clone_security(struct sk_security_struct *ssec,
+void selinux_netlbl_sk_security_clone(struct sk_security_struct *ssec,
                                       struct sk_security_struct *newssec);
 int selinux_netlbl_inode_permission(struct inode *inode, int mask);
 int selinux_netlbl_socket_setsockopt(struct socket *sock,
@@ -62,9 +62,7 @@ static inline void selinux_netlbl_cache_invalidate(void)
         return;
 }
 
-static inline int selinux_netlbl_socket_post_create(struct socket *sock,
-                                                    int sock_family,
-                                                    u32 sid)
+static inline int selinux_netlbl_socket_post_create(struct socket *sock)
 {
         return 0;
 }
@@ -98,6 +96,13 @@ static inline u32 selinux_netlbl_socket_getpeersec_dgram(struct sk_buff *skb)
         return SECSID_NULL;
 }
 
+static inline void selinux_netlbl_sk_security_reset(
+                                               struct sk_security_struct *ssec,
+                                               int family)
+{
+        return;
+}
+
 static inline void selinux_netlbl_sk_security_init(
                                                struct sk_security_struct *ssec,
                                                int family)
@@ -105,7 +110,7 @@ static inline void selinux_netlbl_sk_security_init(
         return;
 }
 
-static inline void selinux_netlbl_sk_clone_security(
+static inline void selinux_netlbl_sk_security_clone(
                                            struct sk_security_struct *ssec,
                                            struct sk_security_struct *newssec)
 {
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index 1f5bbb246d28..b66b454fe72b 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -33,6 +33,7 @@
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/spinlock.h>
+#include <linux/rcupdate.h>
 #include <linux/errno.h>
 #include <linux/in.h>
 #include <linux/sched.h>
@@ -2435,7 +2436,9 @@ static int selinux_netlbl_skbuff_getsid(struct sk_buff *skb,
  *
  * Description:
  * Attempt to label a socket using the NetLabel mechanism using the given
- * SID.  Returns zero values on success, negative values on failure.
+ * SID.  Returns zero values on success, negative values on failure.  The
+ * caller is responsibile for calling rcu_read_lock() before calling this
+ * this function and rcu_read_unlock() after this function returns.
  *
  */
 static int selinux_netlbl_socket_setsid(struct socket *sock, u32 sid)
@@ -2472,8 +2475,11 @@ static int selinux_netlbl_socket_setsid(struct socket *sock, u32 sid)
                 secattr.flags |= NETLBL_SECATTR_MLS_CAT;
 
         rc = netlbl_socket_setattr(sock, &secattr);
-        if (rc == 0)
+        if (rc == 0) {
+                spin_lock(&sksec->nlbl_lock);
                 sksec->nlbl_state = NLBL_LABELED;
+                spin_unlock(&sksec->nlbl_lock);
+        }
 
 netlbl_socket_setsid_return:
         POLICY_RDUNLOCK;
@@ -2482,6 +2488,25 @@ netlbl_socket_setsid_return:
 }
 
 /**
+ * selinux_netlbl_sk_security_reset - Reset the NetLabel fields
+ * @ssec: the sk_security_struct
+ * @family: the socket family
+ *
+ * Description:
+ * Called when the NetLabel state of a sk_security_struct needs to be reset.
+ * The caller is responsibile for all the NetLabel sk_security_struct locking.
+ *
+ */
+void selinux_netlbl_sk_security_reset(struct sk_security_struct *ssec,
+                                      int family)
+{
+        if (family == PF_INET)
+                ssec->nlbl_state = NLBL_REQUIRE;
+        else
+                ssec->nlbl_state = NLBL_UNSET;
+}
+
+/**
  * selinux_netlbl_sk_security_init - Setup the NetLabel fields
  * @ssec: the sk_security_struct
  * @family: the socket family
@@ -2494,14 +2519,13 @@ netlbl_socket_setsid_return:
 void selinux_netlbl_sk_security_init(struct sk_security_struct *ssec,
                                      int family)
 {
-        if (family == PF_INET)
-                ssec->nlbl_state = NLBL_REQUIRE;
-        else
-                ssec->nlbl_state = NLBL_UNSET;
+        /* No locking needed, we are the only one who has access to ssec */
+        selinux_netlbl_sk_security_reset(ssec, family);
+        spin_lock_init(&ssec->nlbl_lock);
 }
 
 /**
- * selinux_netlbl_sk_clone_security - Copy the NetLabel fields
+ * selinux_netlbl_sk_security_clone - Copy the NetLabel fields
  * @ssec: the original sk_security_struct
  * @newssec: the cloned sk_security_struct
  *
@@ -2510,41 +2534,41 @@ void selinux_netlbl_sk_security_init(struct sk_security_struct *ssec,
  * @newssec.
  *
  */
-void selinux_netlbl_sk_clone_security(struct sk_security_struct *ssec,
+void selinux_netlbl_sk_security_clone(struct sk_security_struct *ssec,
                                       struct sk_security_struct *newssec)
 {
+        /* We don't need to take newssec->nlbl_lock because we are the only
+         * thread with access to newssec, but we do need to take the RCU read
+         * lock as other threads could have access to ssec */
+        rcu_read_lock();
+        selinux_netlbl_sk_security_reset(newssec, ssec->sk->sk_family);
         newssec->sclass = ssec->sclass;
-        if (ssec->nlbl_state != NLBL_UNSET)
-                newssec->nlbl_state = NLBL_REQUIRE;
-        else
-                newssec->nlbl_state = NLBL_UNSET;
+        rcu_read_unlock();
 }
 
 /**
  * selinux_netlbl_socket_post_create - Label a socket using NetLabel
  * @sock: the socket to label
- * @sock_family: the socket family
- * @sid: the SID to use
  *
  * Description:
  * Attempt to label a socket using the NetLabel mechanism using the given
  * SID.  Returns zero values on success, negative values on failure.
  *
  */
-int selinux_netlbl_socket_post_create(struct socket *sock,
-                                      int sock_family,
-                                      u32 sid)
+int selinux_netlbl_socket_post_create(struct socket *sock)
 {
+        int rc = 0;
         struct inode_security_struct *isec = SOCK_INODE(sock)->i_security;
         struct sk_security_struct *sksec = sock->sk->sk_security;
 
         sksec->sclass = isec->sclass;
 
-        if (sock_family != PF_INET)
-                return 0;
+        rcu_read_lock();
+        if (sksec->nlbl_state == NLBL_REQUIRE)
+                rc = selinux_netlbl_socket_setsid(sock, sksec->sid);
+        rcu_read_unlock();
 
-        sksec->nlbl_state = NLBL_REQUIRE;
-        return selinux_netlbl_socket_setsid(sock, sid);
+        return rc;
 }
 
 /**
@@ -2566,8 +2590,12 @@ void selinux_netlbl_sock_graft(struct sock *sk, struct socket *sock)
 
         sksec->sclass = isec->sclass;
 
-        if (sk->sk_family != PF_INET)
+        rcu_read_lock();
+
+        if (sksec->nlbl_state != NLBL_REQUIRE) {
+                rcu_read_unlock();
                 return;
+        }
 
         netlbl_secattr_init(&secattr);
         if (netlbl_sock_getattr(sk, &secattr) == 0 &&
@@ -2579,12 +2607,12 @@ void selinux_netlbl_sock_graft(struct sock *sk, struct socket *sock)
                 sksec->peer_sid = nlbl_peer_sid;
         netlbl_secattr_destroy(&secattr);
 
-        sksec->nlbl_state = NLBL_REQUIRE;
-
         /* Try to set the NetLabel on the socket to save time later, if we fail
          * here we will pick up the pieces in later calls to
          * selinux_netlbl_inode_permission(). */
         selinux_netlbl_socket_setsid(sock, sksec->sid);
+
+        rcu_read_unlock();
 }
 
 /**
@@ -2625,25 +2653,24 @@ u32 selinux_netlbl_inet_conn_request(struct sk_buff *skb, u32 sock_sid)
 int selinux_netlbl_inode_permission(struct inode *inode, int mask)
 {
         int rc;
-        struct inode_security_struct *isec;
         struct sk_security_struct *sksec;
         struct socket *sock;
 
-        if (!S_ISSOCK(inode->i_mode))
+        if (!S_ISSOCK(inode->i_mode) ||
+            ((mask & (MAY_WRITE | MAY_APPEND)) == 0))
                 return 0;
-
         sock = SOCKET_I(inode);
-        isec = inode->i_security;
         sksec = sock->sk->sk_security;
-        mutex_lock(&isec->lock);
-        if (unlikely(sksec->nlbl_state == NLBL_REQUIRE &&
-                     (mask & (MAY_WRITE | MAY_APPEND)))) {
-                lock_sock(sock->sk);
-                rc = selinux_netlbl_socket_setsid(sock, sksec->sid);
-                release_sock(sock->sk);
-        } else
-                rc = 0;
-        mutex_unlock(&isec->lock);
+
+        rcu_read_lock();
+        if (sksec->nlbl_state != NLBL_REQUIRE) {
+                rcu_read_unlock();
+                return 0;
+        }
+        lock_sock(sock->sk);
+        rc = selinux_netlbl_socket_setsid(sock, sksec->sid);
+        release_sock(sock->sk);
+        rcu_read_unlock();
 
         return rc;
 }
@@ -2754,12 +2781,10 @@ int selinux_netlbl_socket_setsockopt(struct socket *sock,
                                      int optname)
 {
         int rc = 0;
-        struct inode *inode = SOCK_INODE(sock);
         struct sk_security_struct *sksec = sock->sk->sk_security;
-        struct inode_security_struct *isec = inode->i_security;
         struct netlbl_lsm_secattr secattr;
 
-        mutex_lock(&isec->lock);
+        rcu_read_lock();
         if (level == IPPROTO_IP && optname == IP_OPTIONS &&
             sksec->nlbl_state == NLBL_LABELED) {
                 netlbl_secattr_init(&secattr);
@@ -2768,7 +2793,7 @@ int selinux_netlbl_socket_setsockopt(struct socket *sock,
                         rc = -EACCES;
                 netlbl_secattr_destroy(&secattr);
         }
-        mutex_unlock(&isec->lock);
+        rcu_read_unlock();
 
         return rc;
 }