[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, 2 insertions, 4 deletions

diff --git a/include/net/af_unix.h b/include/net/af_unix.h
index 2fec827c8801..c0398f5a8cb9 100644
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h
@@ -54,15 +54,13 @@ struct unix_skb_parms {
         struct ucred            creds;          /* Skb credentials      */
         struct scm_fp_list      *fp;            /* Passed files         */
 #ifdef CONFIG_SECURITY_NETWORK
-        char                    *secdata;       /* Security context     */
-        u32                     seclen;         /* Security length      */
+        u32                     secid;          /* Security ID          */
 #endif
 };
 
 #define UNIXCB(skb)     (*(struct unix_skb_parms*)&((skb)->cb))
 #define UNIXCREDS(skb)  (&UNIXCB((skb)).creds)
-#define UNIXSECDATA(skb)        (&UNIXCB((skb)).secdata)
-#define UNIXSECLEN(skb)         (&UNIXCB((skb)).seclen)
+#define UNIXSID(skb)    (&UNIXCB((skb)).secid)
 
 #define unix_state_rlock(s)     spin_lock(&unix_sk(s)->lock)
 #define unix_state_runlock(s)   spin_unlock(&unix_sk(s)->lock)