af-unix: passcred support for sendpage

[firefly-linux-kernel-4.4.55.git] / net / unix / af_unix.c

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 4e95bdf973d9a6eb4fd5e565c58444b855b17ca3..6ced74690eeed1ecbeb197ae2aaea43cdec3127b 100644 (file)
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1551,6 +1551,14 @@ static int unix_scm_to_skb(struct scm_cookie *scm, struct sk_buff *skb, bool sen
        return err;
 }
 
+static bool unix_passcred_enabled(const struct socket *sock,
+                                 const struct sock *other)
+{
+       return test_bit(SOCK_PASSCRED, &sock->flags) ||
+              !other->sk_socket ||
+              test_bit(SOCK_PASSCRED, &other->sk_socket->flags);
+}
+
 /*
  * Some apps rely on write() giving SCM_CREDENTIALS
  * We include credentials if source or destination socket
@@ -1561,14 +1569,41 @@ static void maybe_add_creds(struct sk_buff *skb, const struct socket *sock,
 {
        if (UNIXCB(skb).pid)
                return;
-       if (test_bit(SOCK_PASSCRED, &sock->flags) ||
-           !other->sk_socket ||
-           test_bit(SOCK_PASSCRED, &other->sk_socket->flags)) {
+       if (unix_passcred_enabled(sock, other)) {
                UNIXCB(skb).pid  = get_pid(task_tgid(current));
                current_uid_gid(&UNIXCB(skb).uid, &UNIXCB(skb).gid);
        }
 }
 
+static int maybe_init_creds(struct scm_cookie *scm,
+                           struct socket *socket,
+                           const struct sock *other)
+{
+       int err;
+       struct msghdr msg = { .msg_controllen = 0 };
+
+       err = scm_send(socket, &msg, scm, false);
+       if (err)
+               return err;
+
+       if (unix_passcred_enabled(socket, other)) {
+               scm->pid = get_pid(task_tgid(current));
+               current_uid_gid(&scm->creds.uid, &scm->creds.gid);
+       }
+       return err;
+}
+
+static bool unix_skb_scm_eq(struct sk_buff *skb,
+                           struct scm_cookie *scm)
+{
+       const struct unix_skb_parms *u = &UNIXCB(skb);
+
+       return u->pid == scm->pid &&
+              uid_eq(u->uid, scm->creds.uid) &&
+              gid_eq(u->gid, scm->creds.gid) &&
+              unix_secdata_eq(scm, skb);
+}
+
 /*
  *     Send AF_UNIX data.
  */
@@ -1884,8 +1919,10 @@ out_err:
 static ssize_t unix_stream_sendpage(struct socket *socket, struct page *page,
                                    int offset, size_t size, int flags)
 {
-       int err = 0;
-       bool send_sigpipe = true;
+       int err;
+       bool send_sigpipe = false;
+       bool init_scm = true;
+       struct scm_cookie scm;
        struct sock *other, *sk = socket->sk;
        struct sk_buff *skb, *newskb = NULL, *tail = NULL;
 
@@ -1903,7 +1940,7 @@ alloc_skb:
                newskb = sock_alloc_send_pskb(sk, 0, 0, flags & MSG_DONTWAIT,
                                              &err, 0);
                if (!newskb)
-                       return err;
+                       goto err;
        }
 
        /* we must acquire readlock as we modify already present
@@ -1912,12 +1949,12 @@ alloc_skb:
        err = mutex_lock_interruptible(&unix_sk(other)->readlock);
        if (err) {
                err = flags & MSG_DONTWAIT ? -EAGAIN : -ERESTARTSYS;
-               send_sigpipe = false;
                goto err;
        }
 
        if (sk->sk_shutdown & SEND_SHUTDOWN) {
                err = -EPIPE;
+               send_sigpipe = true;
                goto err_unlock;
        }
 
@@ -1926,17 +1963,27 @@ alloc_skb:
        if (sock_flag(other, SOCK_DEAD) ||
            other->sk_shutdown & RCV_SHUTDOWN) {
                err = -EPIPE;
+               send_sigpipe = true;
                goto err_state_unlock;
        }
 
+       if (init_scm) {
+               err = maybe_init_creds(&scm, socket, other);
+               if (err)
+                       goto err_state_unlock;
+               init_scm = false;
+       }
+
        skb = skb_peek_tail(&other->sk_receive_queue);
        if (tail && tail == skb) {
                skb = newskb;
-       } else if (!skb) {
-               if (newskb)
+       } else if (!skb || !unix_skb_scm_eq(skb, &scm)) {
+               if (newskb) {
                        skb = newskb;
-               else
+               } else {
+                       tail = skb;
                        goto alloc_skb;
+               }
        } else if (newskb) {
                /* this is fast path, we don't necessarily need to
                 * call to kfree_skb even though with newskb == NULL
@@ -1957,6 +2004,9 @@ alloc_skb:
        atomic_add(size, &sk->sk_wmem_alloc);
 
        if (newskb) {
+               err = unix_scm_to_skb(&scm, skb, false);
+               if (err)
+                       goto err_state_unlock;
                spin_lock(&other->sk_receive_queue.lock);
                __skb_queue_tail(&other->sk_receive_queue, newskb);
                spin_unlock(&other->sk_receive_queue.lock);
@@ -1966,7 +2016,7 @@ alloc_skb:
        mutex_unlock(&unix_sk(other)->readlock);
 
        other->sk_data_ready(other);
-
+       scm_destroy(&scm);
        return size;
 
 err_state_unlock:
@@ -1977,6 +2027,8 @@ err:
        kfree_skb(newskb);
        if (send_sigpipe && !(flags & MSG_NOSIGNAL))
                send_sig(SIGPIPE, current, 0);
+       if (!init_scm)
+               scm_destroy(&scm);
        return err;
 }
 
@@ -2280,10 +2332,7 @@ unlock:
 
                if (check_creds) {
                        /* Never glue messages from different writers */
-                       if ((UNIXCB(skb).pid  != scm.pid) ||
-                           !uid_eq(UNIXCB(skb).uid, scm.creds.uid) ||
-                           !gid_eq(UNIXCB(skb).gid, scm.creds.gid) ||
-                           !unix_secdata_eq(&scm, skb))
+                       if (!unix_skb_scm_eq(skb, &scm))
                                break;
                } else if (test_bit(SOCK_PASSCRED, &sock->flags)) {
                        /* Copy credentials */