[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, 12 insertions, 2 deletions

diff --git a/security/dummy.c b/security/dummy.c
index bbbfda70e131..58c6d399c844 100644
--- a/security/dummy.c
+++ b/security/dummy.c
@@ -791,8 +791,7 @@ static int dummy_socket_getpeersec_stream(struct socket *sock, char __user *optv
         return -ENOPROTOOPT;
 }
 
-static int dummy_socket_getpeersec_dgram(struct sk_buff *skb, char **secdata,
-                                         u32 *seclen)
+static int dummy_socket_getpeersec_dgram(struct socket *sock, struct sk_buff *skb, u32 *secid)
 {
         return -ENOPROTOOPT;
 }
@@ -876,6 +875,15 @@ static int dummy_setprocattr(struct task_struct *p, char *name, void *value, siz
         return -EINVAL;
 }
 
+static int dummy_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
+{
+        return -EOPNOTSUPP;
+}
+
+static void dummy_release_secctx(char *secdata, u32 seclen)
+{
+}
+
 #ifdef CONFIG_KEYS
 static inline int dummy_key_alloc(struct key *key, struct task_struct *ctx,
                                   unsigned long flags)
@@ -1028,6 +1036,8 @@ void security_fixup_ops (struct security_operations *ops)
         set_to_dummy_if_null(ops, d_instantiate);
         set_to_dummy_if_null(ops, getprocattr);
         set_to_dummy_if_null(ops, setprocattr);
+        set_to_dummy_if_null(ops, secid_to_secctx);
+        set_to_dummy_if_null(ops, release_secctx);
 #ifdef CONFIG_SECURITY_NETWORK
         set_to_dummy_if_null(ops, unix_stream_connect);
         set_to_dummy_if_null(ops, unix_may_send);