[AF_UNIX]: Kernel memory leak fix for af_unix datagram getpeersec patch

From: Catherine Zhang <cxzhang@watson.ibm.com>

This patch implements a cleaner fix for the memory leak problem of the
original unix datagram getpeersec patch.  Instead of creating a
security context each time a unix datagram is sent, we only create the
security context when the receiver requests it.

This new design requires modification of the current
unix_getsecpeer_dgram LSM hook and addition of two new hooks, namely,
secid_to_secctx and release_secctx.  The former retrieves the security
context and the latter releases it.  A hook is required for releasing
the security context because it is up to the security module to decide
how that's done.  In the case of Selinux, it's a simple kfree
operation.

Acked-by:  Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 35 insertions, 6 deletions

diff --git a/include/linux/security.h b/include/linux/security.h
index f75303831d09..aa5b8043dc38 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1109,6 +1109,16 @@ struct swap_info_struct;
  *      @name contains the name of the security module being unstacked.
  *      @ops contains a pointer to the struct security_operations of the module to unstack.
  * 
+ * @secid_to_secctx:
+ *      Convert secid to security context.
+ *      @secid contains the security ID.
+ *      @secdata contains the pointer that stores the converted security context.
+ *
+ * @release_secctx:
+ *      Release the security context.
+ *      @secdata contains the security context.
+ *      @seclen contains the length of the security context.
+ *
  * This is the main security structure.
  */
 struct security_operations {
@@ -1289,6 +1299,8 @@ struct security_operations {
 
         int (*getprocattr)(struct task_struct *p, char *name, void *value, size_t size);
         int (*setprocattr)(struct task_struct *p, char *name, void *value, size_t size);
+        int (*secid_to_secctx)(u32 secid, char **secdata, u32 *seclen);
+        void (*release_secctx)(char *secdata, u32 seclen);
 
 #ifdef CONFIG_SECURITY_NETWORK
         int (*unix_stream_connect) (struct socket * sock,
@@ -1317,7 +1329,7 @@ struct security_operations {
         int (*socket_shutdown) (struct socket * sock, int how);
         int (*socket_sock_rcv_skb) (struct sock * sk, struct sk_buff * skb);
         int (*socket_getpeersec_stream) (struct socket *sock, char __user *optval, int __user *optlen, unsigned len);
-        int (*socket_getpeersec_dgram) (struct sk_buff *skb, char **secdata, u32 *seclen);
+        int (*socket_getpeersec_dgram) (struct socket *sock, struct sk_buff *skb, u32 *secid);
         int (*sk_alloc_security) (struct sock *sk, int family, gfp_t priority);
         void (*sk_free_security) (struct sock *sk);
         unsigned int (*sk_getsid) (struct sock *sk, struct flowi *fl, u8 dir);
@@ -2059,6 +2071,16 @@ static inline int security_netlink_recv(struct sk_buff * skb, int cap)
         return security_ops->netlink_recv(skb, cap);
 }
 
+static inline int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
+{
+        return security_ops->secid_to_secctx(secid, secdata, seclen);
+}
+
+static inline void security_release_secctx(char *secdata, u32 seclen)
+{
+        return security_ops->release_secctx(secdata, seclen);
+}
+
 /* prototypes */
 extern int security_init        (void);
 extern int register_security    (struct security_operations *ops);
@@ -2725,6 +2747,15 @@ static inline void securityfs_remove(struct dentry *dentry)
 {
 }
 
+static inline int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
+{
+        return -EOPNOTSUPP;
+}
+
+static inline void security_release_secctx(char *secdata, u32 seclen)
+{
+        return -EOPNOTSUPP;
+}
 #endif  /* CONFIG_SECURITY */
 
 #ifdef CONFIG_SECURITY_NETWORK
@@ -2840,10 +2871,9 @@ static inline int security_socket_getpeersec_stream(struct socket *sock, char __
         return security_ops->socket_getpeersec_stream(sock, optval, optlen, len);
 }
 
-static inline int security_socket_getpeersec_dgram(struct sk_buff *skb, char **secdata,
-                                                   u32 *seclen)
+static inline int security_socket_getpeersec_dgram(struct socket *sock, struct sk_buff *skb, u32 *secid)
 {
-        return security_ops->socket_getpeersec_dgram(skb, secdata, seclen);
+        return security_ops->socket_getpeersec_dgram(sock, skb, secid);
 }
 
 static inline int security_sk_alloc(struct sock *sk, int family, gfp_t priority)
@@ -2968,8 +2998,7 @@ static inline int security_socket_getpeersec_stream(struct socket *sock, char __
         return -ENOPROTOOPT;
 }
 
-static inline int security_socket_getpeersec_dgram(struct sk_buff *skb, char **secdata,
-                                                   u32 *seclen)
+static inline int security_socket_getpeersec_dgram(struct socket *sock, struct sk_buff *skb, u32 *secid)
 {
         return -ENOPROTOOPT;
 }