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

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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>
This commit is contained in:
Catherine Zhang 2006-08-02 14:12:06 -07:00 • committed by David S. Miller
parent 2b7e24b66d
commit dc49c1f94e
7 changed files with 110 additions and 44 deletions
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29
include/net/scm.h
View file

@ -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 scm_cookie
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 int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie
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 @@ static __inline__ int scm_send(struct socket *sock, struct msghdr *msg,
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 @@ static __inline__ int scm_send(struct socket *sock, struct msghdr *msg,
#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)