[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, 7 insertions, 2 deletions

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 84f43a3c9098..2d05c4133d3e 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -112,14 +112,19 @@ static void ip_cmsg_recv_retopts(struct msghdr *msg, struct sk_buff *skb)
 static void ip_cmsg_recv_security(struct msghdr *msg, struct sk_buff *skb)
 {
         char *secdata;
-        u32 seclen;
+        u32 seclen, secid;
         int err;
 
-        err = security_socket_getpeersec_dgram(skb, &secdata, &seclen);
+        err = security_socket_getpeersec_dgram(NULL, skb, &secid);
+        if (err)
+                return;
+
+        err = security_secid_to_secctx(secid, &secdata, &seclen);
         if (err)
                 return;
 
         put_cmsg(msg, SOL_IP, SCM_SECURITY, seclen, secdata);
+        security_release_secctx(secdata, seclen);
 }