[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>
diff --git a/include/net/scm.h b/include/net/scm.h
index 02daa09..5637d5e 100644
--- a/include/net/scm.h
+++ b/include/net/scm.h
@@ -3,6 +3,7 @@
#include <linux/limits.h>
#include <linux/net.h>
+#include <linux/security.h>
/* Well, we should have at least one descriptor open
* to accept passed FDs 8)
@@ -20,8 +21,7 @@
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; /* Passed security ID */
#endif
unsigned long seq; /* Connection seqno */
};
@@ -32,6 +32,16 @@
extern void __scm_destroy(struct scm_cookie *scm);
extern struct scm_fp_list * scm_fp_dup(struct scm_fp_list *fpl);
+#ifdef CONFIG_SECURITY_NETWORK
+static __inline__ void unix_get_peersec_dgram(struct socket *sock, struct scm_cookie *scm)
+{
+ security_socket_getpeersec_dgram(sock, NULL, &scm->secid);
+}
+#else
+static __inline__ void unix_get_peersec_dgram(struct socket *sock, struct scm_cookie *scm)
+{ }
+#endif /* CONFIG_SECURITY_NETWORK */
+
static __inline__ void scm_destroy(struct scm_cookie *scm)
{
if (scm && scm->fp)
@@ -47,6 +57,7 @@
scm->creds.pid = p->tgid;
scm->fp = NULL;
scm->seq = 0;
+ unix_get_peersec_dgram(sock, scm);
if (msg->msg_controllen <= 0)
return 0;
return __scm_send(sock, msg, scm);
@@ -55,8 +66,18 @@
#ifdef CONFIG_SECURITY_NETWORK
static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm)
{
- if (test_bit(SOCK_PASSSEC, &sock->flags) && scm->secdata != NULL)
- put_cmsg(msg, SOL_SOCKET, SCM_SECURITY, scm->seclen, scm->secdata);
+ char *secdata;
+ u32 seclen;
+ int err;
+
+ if (test_bit(SOCK_PASSSEC, &sock->flags)) {
+ err = security_secid_to_secctx(scm->secid, &secdata, &seclen);
+
+ if (!err) {
+ put_cmsg(msg, SOL_SOCKET, SCM_SECURITY, seclen, secdata);
+ security_release_secctx(secdata, seclen);
+ }
+ }
}
#else
static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm)