Re: [Patch] kernel memory leak fix for af_unix datagram getpeersecpatch

From: Stephen Smalley
Date: Wed Aug 02 2006 - 08:45:09 EST

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On Wed, 2006-08-02 at 02:47 -0400, Catherine Zhang wrote:
> Hi, all,
>
> Enclosed please find the updated patch incorporating comments from
> Stephen and Dave.

Note that this patch is intended for 2.6.18 as a bug fix for the memory
leak introduced by the original dgram peersec patches.

> Again thanks for your help!
> Catherine
>
> --
>
>
> From: cxzhang@xxxxxxxxxxxxxx
>
> 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@xxxxxxxxxxxxx>

>
>
> ---
>
> include/linux/security.h | 41 +++++++++++++++++++++++++++++++++++------
> include/net/af_unix.h | 6 ++----
> include/net/scm.h | 29 +++++++++++++++++++++++++----
> net/ipv4/ip_sockglue.c | 9 +++++++--
> net/unix/af_unix.c | 17 +++++------------
> security/dummy.c | 14 ++++++++++++--
> security/selinux/hooks.c | 38 ++++++++++++++++++++++++--------------
> 7 files changed, 110 insertions(+), 44 deletions(-)
>
> diff -puN include/net/scm.h~af_unix-datagram-getpeersec-ml-fix include/net/scm.h
> --- linux-2.6.18-rc2/include/net/scm.h~af_unix-datagram-getpeersec-ml-fix 2006-07-22 21:28:21.000000000 -0400
> +++ linux-2.6.18-rc2-cxzhang/include/net/scm.h 2006-08-01 22:43:50.000000000 -0400
> @@ -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 *soc
> 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 so
> 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 so
> #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)
> diff -puN net/unix/af_unix.c~af_unix-datagram-getpeersec-ml-fix net/unix/af_unix.c
> --- linux-2.6.18-rc2/net/unix/af_unix.c~af_unix-datagram-getpeersec-ml-fix 2006-07-22 23:01:26.000000000 -0400
> +++ linux-2.6.18-rc2-cxzhang/net/unix/af_unix.c 2006-08-02 02:25:00.454243480 -0400
> @@ -128,23 +128,17 @@ static atomic_t unix_nr_socks = ATOMIC_I
> #define UNIX_ABSTRACT(sk) (unix_sk(sk)->addr->hash != UNIX_HASH_SIZE)
>
> #ifdef CONFIG_SECURITY_NETWORK
> -static void unix_get_peersec_dgram(struct sk_buff *skb)
> +static void unix_get_secdata(struct scm_cookie *scm, struct sk_buff *skb)
> {
> - int err;
> -
> - err = security_socket_getpeersec_dgram(skb, UNIXSECDATA(skb),
> - UNIXSECLEN(skb));
> - if (err)
> - *(UNIXSECDATA(skb)) = NULL;
> + memcpy(UNIXSID(skb), &scm->secid, sizeof(u32));
> }
>
> static inline void unix_set_secdata(struct scm_cookie *scm, struct sk_buff *skb)
> {
> - scm->secdata = *UNIXSECDATA(skb);
> - scm->seclen = *UNIXSECLEN(skb);
> + scm->secid = *UNIXSID(skb);
> }
> #else
> -static inline void unix_get_peersec_dgram(struct sk_buff *skb)
> +static inline void unix_get_secdata(struct scm_cookie *scm, struct sk_buff *skb)
> { }
>
> static inline void unix_set_secdata(struct scm_cookie *scm, struct sk_buff *skb)
> @@ -1323,8 +1317,7 @@ static int unix_dgram_sendmsg(struct kio
> memcpy(UNIXCREDS(skb), &siocb->scm->creds, sizeof(struct ucred));
> if (siocb->scm->fp)
> unix_attach_fds(siocb->scm, skb);
> -
> - unix_get_peersec_dgram(skb);
> + unix_get_secdata(siocb->scm, skb);
>
> skb->h.raw = skb->data;
> err = memcpy_fromiovec(skb_put(skb,len), msg->msg_iov, len);
> diff -puN include/net/af_unix.h~af_unix-datagram-getpeersec-ml-fix include/net/af_unix.h
> --- linux-2.6.18-rc2/include/net/af_unix.h~af_unix-datagram-getpeersec-ml-fix 2006-07-22 23:41:05.000000000 -0400
> +++ linux-2.6.18-rc2-cxzhang/include/net/af_unix.h 2006-08-01 22:50:20.000000000 -0400
> @@ -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)
> diff -puN include/linux/security.h~af_unix-datagram-getpeersec-ml-fix include/linux/security.h
> --- linux-2.6.18-rc2/include/linux/security.h~af_unix-datagram-getpeersec-ml-fix 2006-07-23 17:49:18.000000000 -0400
> +++ linux-2.6.18-rc2-cxzhang/include/linux/security.h 2006-08-01 23:30:32.000000000 -0400
> @@ -1109,6 +1109,16 @@ struct swap_info_struct;
> * @name contains the name of the security module being unstacked.
> * @ops contains a pointer to the struct security_operations of the module to unstack.
> *
> + * @secid_to_secctx:
> + * Convert secid to security context.
> + * @secid contains the security ID.
> + * @secdata contains the pointer that stores the converted security context.
> + *
> + * @release_secctx:
> + * Release the security context.
> + * @secdata contains the security context.
> + * @seclen contains the length of the security context.
> + *
> * This is the main security structure.
> */
> struct security_operations {
> @@ -1289,6 +1299,8 @@ struct security_operations {
>
> int (*getprocattr)(struct task_struct *p, char *name, void *value, size_t size);
> int (*setprocattr)(struct task_struct *p, char *name, void *value, size_t size);
> + int (*secid_to_secctx)(u32 secid, char **secdata, u32 *seclen);
> + void (*release_secctx)(char *secdata, u32 seclen);
>
> #ifdef CONFIG_SECURITY_NETWORK
> int (*unix_stream_connect) (struct socket * sock,
> @@ -1317,7 +1329,7 @@ struct security_operations {
> int (*socket_shutdown) (struct socket * sock, int how);
> int (*socket_sock_rcv_skb) (struct sock * sk, struct sk_buff * skb);
> int (*socket_getpeersec_stream) (struct socket *sock, char __user *optval, int __user *optlen, unsigned len);
> - int (*socket_getpeersec_dgram) (struct sk_buff *skb, char **secdata, u32 *seclen);
> + int (*socket_getpeersec_dgram) (struct socket *sock, struct sk_buff *skb, u32 *secid);
> int (*sk_alloc_security) (struct sock *sk, int family, gfp_t priority);
> void (*sk_free_security) (struct sock *sk);
> unsigned int (*sk_getsid) (struct sock *sk, struct flowi *fl, u8 dir);
> @@ -2059,6 +2071,16 @@ static inline int security_netlink_recv(
> return security_ops->netlink_recv(skb, cap);
> }
>
> +static inline int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
> +{
> + return security_ops->secid_to_secctx(secid, secdata, seclen);
> +}
> +
> +static inline void security_release_secctx(char *secdata, u32 seclen)
> +{
> + return security_ops->release_secctx(secdata, seclen);
> +}
> +
> /* prototypes */
> extern int security_init (void);
> extern int register_security (struct security_operations *ops);
> @@ -2725,6 +2747,15 @@ static inline void securityfs_remove(str
> {
> }
>
> +static inline int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
> +{
> + return -EOPNOTSUPP;
> +}
> +
> +static inline void security_release_secctx(char *secdata, u32 seclen)
> +{
> + return -EOPNOTSUPP;
> +}
> #endif /* CONFIG_SECURITY */
>
> #ifdef CONFIG_SECURITY_NETWORK
> @@ -2840,10 +2871,9 @@ static inline int security_socket_getpee
> return security_ops->socket_getpeersec_stream(sock, optval, optlen, len);
> }
>
> -static inline int security_socket_getpeersec_dgram(struct sk_buff *skb, char **secdata,
> - u32 *seclen)
> +static inline int security_socket_getpeersec_dgram(struct socket *sock, struct sk_buff *skb, u32 *secid)
> {
> - return security_ops->socket_getpeersec_dgram(skb, secdata, seclen);
> + return security_ops->socket_getpeersec_dgram(sock, skb, secid);
> }
>
> static inline int security_sk_alloc(struct sock *sk, int family, gfp_t priority)
> @@ -2968,8 +2998,7 @@ static inline int security_socket_getpee
> return -ENOPROTOOPT;
> }
>
> -static inline int security_socket_getpeersec_dgram(struct sk_buff *skb, char **secdata,
> - u32 *seclen)
> +static inline int security_socket_getpeersec_dgram(struct socket *sock, struct sk_buff *skb, u32 *secid)
> {
> return -ENOPROTOOPT;
> }
> diff -puN security/selinux/hooks.c~af_unix-datagram-getpeersec-ml-fix security/selinux/hooks.c
> --- linux-2.6.18-rc2/security/selinux/hooks.c~af_unix-datagram-getpeersec-ml-fix 2006-07-24 00:55:21.000000000 -0400
> +++ linux-2.6.18-rc2-cxzhang/security/selinux/hooks.c 2006-08-01 23:58:17.000000000 -0400
> @@ -3524,25 +3524,21 @@ out:
> return err;
> }
>
> -static int selinux_socket_getpeersec_dgram(struct sk_buff *skb, char **secdata, u32 *seclen)
> +static int selinux_socket_getpeersec_dgram(struct socket *sock, struct sk_buff *skb, u32 *secid)
> {
> + u32 peer_secid = SECSID_NULL;
> int err = 0;
> - u32 peer_sid;
>
> - if (skb->sk->sk_family == PF_UNIX)
> - selinux_get_inode_sid(SOCK_INODE(skb->sk->sk_socket),
> - &peer_sid);
> - else
> - peer_sid = selinux_socket_getpeer_dgram(skb);
> -
> - if (peer_sid == SECSID_NULL)
> - return -EINVAL;
> + if (sock && (sock->sk->sk_family == PF_UNIX))
> + selinux_get_inode_sid(SOCK_INODE(sock), &peer_secid);
> + else if (skb)
> + peer_secid = selinux_socket_getpeer_dgram(skb);
>
> - err = security_sid_to_context(peer_sid, secdata, seclen);
> - if (err)
> - return err;
> + if (peer_secid == SECSID_NULL)
> + err = -EINVAL;
> + *secid = peer_secid;
>
> - return 0;
> + return err;
> }
>
> static int selinux_sk_alloc_security(struct sock *sk, int family, gfp_t priority)
> @@ -4407,6 +4403,17 @@ static int selinux_setprocattr(struct ta
> return size;
> }
>
> +static int selinux_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
> +{
> + return security_sid_to_context(secid, secdata, seclen);
> +}
> +
> +static void selinux_release_secctx(char *secdata, u32 seclen)
> +{
> + if (secdata)
> + kfree(secdata);
> +}
> +
> #ifdef CONFIG_KEYS
>
> static int selinux_key_alloc(struct key *k, struct task_struct *tsk,
> @@ -4587,6 +4594,9 @@ static struct security_operations selinu
> .getprocattr = selinux_getprocattr,
> .setprocattr = selinux_setprocattr,
>
> + .secid_to_secctx = selinux_secid_to_secctx,
> + .release_secctx = selinux_release_secctx,
> +
> .unix_stream_connect = selinux_socket_unix_stream_connect,
> .unix_may_send = selinux_socket_unix_may_send,
>
> diff -puN security/dummy.c~af_unix-datagram-getpeersec-ml-fix security/dummy.c
> --- linux-2.6.18-rc2/security/dummy.c~af_unix-datagram-getpeersec-ml-fix 2006-07-24 01:01:07.000000000 -0400
> +++ linux-2.6.18-rc2-cxzhang/security/dummy.c 2006-08-01 23:37:48.000000000 -0400
> @@ -791,8 +791,7 @@ static int dummy_socket_getpeersec_strea
> 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
> 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
> 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);
> diff -puN net/ipv4/ip_sockglue.c~af_unix-datagram-getpeersec-ml-fix net/ipv4/ip_sockglue.c
> --- linux-2.6.18-rc2/net/ipv4/ip_sockglue.c~af_unix-datagram-getpeersec-ml-fix 2006-07-24 18:42:18.000000000 -0400
> +++ linux-2.6.18-rc2-cxzhang/net/ipv4/ip_sockglue.c 2006-08-01 23:09:50.000000000 -0400
> @@ -112,14 +112,19 @@ static void ip_cmsg_recv_retopts(struct
> 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);
> }
>
>
> _
> -

--
Stephen Smalley
National Security Agency

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