2 files changed, 48 insertions, 19 deletions

diff --git a/include/net/scm.h b/include/net/scm.h
index 745460fa2f02..68e1e481658e 100644
--- a/include/net/scm.h
+++ b/include/net/scm.h
@@ -53,6 +53,14 @@ static __inline__ void scm_set_cred(struct scm_cookie *scm,
         cred_to_ucred(pid, cred, &scm->creds);
 }
 
+static __inline__ void scm_set_cred_noref(struct scm_cookie *scm,
+                                    struct pid *pid, const struct cred *cred)
+{
+        scm->pid  = pid;
+        scm->cred = cred;
+        cred_to_ucred(pid, cred, &scm->creds);
+}
+
 static __inline__ void scm_destroy_cred(struct scm_cookie *scm)
 {
         put_pid(scm->pid);
@@ -70,6 +78,15 @@ static __inline__ void scm_destroy(struct scm_cookie *scm)
                 __scm_destroy(scm);
 }
 
+static __inline__ void scm_release(struct scm_cookie *scm)
+{
+        /* keep ref on pid and cred */
+        scm->pid = NULL;
+        scm->cred = NULL;
+        if (scm->fp)
+                __scm_destroy(scm);
+}
+
 static __inline__ int scm_send(struct socket *sock, struct msghdr *msg,
                                struct scm_cookie *scm)
 {
@@ -108,15 +125,14 @@ static __inline__ void scm_recv(struct socket *sock, struct msghdr *msg,
         if (!msg->msg_control) {
                 if (test_bit(SOCK_PASSCRED, &sock->flags) || scm->fp)
                         msg->msg_flags |= MSG_CTRUNC;
-                scm_destroy(scm);
+                if (scm && scm->fp)
+                        __scm_destroy(scm);
                 return;
         }
 
         if (test_bit(SOCK_PASSCRED, &sock->flags))
                 put_cmsg(msg, SOL_SOCKET, SCM_CREDENTIALS, sizeof(scm->creds), &scm->creds);
 
-        scm_destroy_cred(scm);
-
         scm_passec(sock, msg, scm);
 
         if (!scm->fp)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index ec68e1c05b85..e6d9d1014ed2 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1378,11 +1378,17 @@ static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
         return max_level;
 }
 
-static int unix_scm_to_skb(struct scm_cookie *scm, struct sk_buff *skb, bool send_fds)
+static int unix_scm_to_skb(struct scm_cookie *scm, struct sk_buff *skb,
+                           bool send_fds, bool ref)
 {
         int err = 0;
-        UNIXCB(skb).pid  = get_pid(scm->pid);
-        UNIXCB(skb).cred = get_cred(scm->cred);
+        if (ref) {
+                UNIXCB(skb).pid  = get_pid(scm->pid);
+                UNIXCB(skb).cred = get_cred(scm->cred);
+        } else {
+                UNIXCB(skb).pid  = scm->pid;
+                UNIXCB(skb).cred = scm->cred;
+        }
         UNIXCB(skb).fp = NULL;
         if (scm->fp && send_fds)
                 err = unix_attach_fds(scm, skb);
@@ -1407,7 +1413,7 @@ static int unix_dgram_sendmsg(struct kiocb *kiocb, struct socket *sock,
         int namelen = 0; /* fake GCC */
         int err;
         unsigned hash;
-        struct sk_buff *skb;
+        struct sk_buff *skb = NULL;
         long timeo;
         struct scm_cookie tmp_scm;
         int max_level;
@@ -1448,7 +1454,7 @@ static int unix_dgram_sendmsg(struct kiocb *kiocb, struct socket *sock,
         if (skb == NULL)
                 goto out;
 
-        err = unix_scm_to_skb(siocb->scm, skb, true);
+        err = unix_scm_to_skb(siocb->scm, skb, true, false);
         if (err < 0)
                 goto out_free;
         max_level = err + 1;
@@ -1544,7 +1550,7 @@ restart:
         unix_state_unlock(other);
         other->sk_data_ready(other, len);
         sock_put(other);
-        scm_destroy(siocb->scm);
+        scm_release(siocb->scm);
         return len;
 
 out_unlock:
@@ -1554,7 +1560,8 @@ out_free:
 out:
         if (other)
                 sock_put(other);
-        scm_destroy(siocb->scm);
+        if (skb == NULL)
+                scm_destroy(siocb->scm);
         return err;
 }
 
@@ -1566,7 +1573,7 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
         struct sock *sk = sock->sk;
         struct sock *other = NULL;
         int err, size;
-        struct sk_buff *skb;
+        struct sk_buff *skb = NULL;
         int sent = 0;
         struct scm_cookie tmp_scm;
         bool fds_sent = false;
@@ -1631,11 +1638,11 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
                 size = min_t(int, size, skb_tailroom(skb));
 
 
-                /* Only send the fds in the first buffer */
-                err = unix_scm_to_skb(siocb->scm, skb, !fds_sent);
+                /* Only send the fds and no ref to pid in the first buffer */
+                err = unix_scm_to_skb(siocb->scm, skb, !fds_sent, fds_sent);
                 if (err < 0) {
                         kfree_skb(skb);
-                        goto out_err;
+                        goto out;
                 }
                 max_level = err + 1;
                 fds_sent = true;
@@ -1643,7 +1650,7 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
                 err = memcpy_fromiovec(skb_put(skb, size), msg->msg_iov, size);
                 if (err) {
                         kfree_skb(skb);
-                        goto out_err;
+                        goto out;
                 }
 
                 unix_state_lock(other);
@@ -1660,7 +1667,10 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
                 sent += size;
         }
 
-        scm_destroy(siocb->scm);
+        if (skb)
+                scm_release(siocb->scm);
+        else
+                scm_destroy(siocb->scm);
         siocb->scm = NULL;
 
         return sent;
@@ -1673,7 +1683,9 @@ pipe_err:
                 send_sig(SIGPIPE, current, 0);
         err = -EPIPE;
 out_err:
-        scm_destroy(siocb->scm);
+        if (skb == NULL)
+                scm_destroy(siocb->scm);
+out:
         siocb->scm = NULL;
         return sent ? : err;
 }
@@ -1777,7 +1789,7 @@ static int unix_dgram_recvmsg(struct kiocb *iocb, struct socket *sock,
                 siocb->scm = &tmp_scm;
                 memset(&tmp_scm, 0, sizeof(tmp_scm));
         }
-        scm_set_cred(siocb->scm, UNIXCB(skb).pid, UNIXCB(skb).cred);
+        scm_set_cred_noref(siocb->scm, UNIXCB(skb).pid, UNIXCB(skb).cred);
         unix_set_secdata(siocb->scm, skb);
 
         if (!(flags & MSG_PEEK)) {
@@ -1939,7 +1951,8 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
                         }
                 } else {
                         /* Copy credentials */
-                        scm_set_cred(siocb->scm, UNIXCB(skb).pid, UNIXCB(skb).cred);
+                        scm_set_cred_noref(siocb->scm, UNIXCB(skb).pid,
+                                           UNIXCB(skb).cred);
                         check_creds = 1;
                 }