Merge branch 'next' into for-linus

1 files changed, 23 insertions, 1 deletions

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index ec68e1c05b85..466fbcc5cf77 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1381,8 +1381,10 @@ static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
 static int unix_scm_to_skb(struct scm_cookie *scm, struct sk_buff *skb, bool send_fds)
 {
         int err = 0;
+
         UNIXCB(skb).pid  = get_pid(scm->pid);
-        UNIXCB(skb).cred = get_cred(scm->cred);
+        if (scm->cred)
+                UNIXCB(skb).cred = get_cred(scm->cred);
         UNIXCB(skb).fp = NULL;
         if (scm->fp && send_fds)
                 err = unix_attach_fds(scm, skb);
@@ -1392,6 +1394,24 @@ static int unix_scm_to_skb(struct scm_cookie *scm, struct sk_buff *skb, bool sen
 }
 
 /*
+ * Some apps rely on write() giving SCM_CREDENTIALS
+ * We include credentials if source or destination socket
+ * asserted SOCK_PASSCRED.
+ */
+static void maybe_add_creds(struct sk_buff *skb, const struct socket *sock,
+                            const struct sock *other)
+{
+        if (UNIXCB(skb).cred)
+                return;
+        if (test_bit(SOCK_PASSCRED, &sock->flags) ||
+            !other->sk_socket ||
+            test_bit(SOCK_PASSCRED, &other->sk_socket->flags)) {
+                UNIXCB(skb).pid  = get_pid(task_tgid(current));
+                UNIXCB(skb).cred = get_current_cred();
+        }
+}
+
+/*
  *      Send AF_UNIX data.
  */
 
@@ -1538,6 +1558,7 @@ restart:
 
         if (sock_flag(other, SOCK_RCVTSTAMP))
                 __net_timestamp(skb);
+        maybe_add_creds(skb, sock, other);
         skb_queue_tail(&other->sk_receive_queue, skb);
         if (max_level > unix_sk(other)->recursion_level)
                 unix_sk(other)->recursion_level = max_level;
@@ -1652,6 +1673,7 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
                     (other->sk_shutdown & RCV_SHUTDOWN))
                         goto pipe_err_free;
 
+                maybe_add_creds(skb, sock, other);
                 skb_queue_tail(&other->sk_receive_queue, skb);
                 if (max_level > unix_sk(other)->recursion_level)
                         unix_sk(other)->recursion_level = max_level;