caif: Bugfix - use MSG_TRUNC in receive

Fixed handling when skb don't fit in user buffer,
instead of returning -EMSGSIZE, the buffer is truncated (just
as unix seqpakcet does).

Signed-off-by: Sjur Braendeland <sjur.brandeland@stericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 18 insertions, 29 deletions

diff --git a/net/caif/caif_socket.c b/net/caif/caif_socket.c
index 691a5710974e..3d0e09584fae 100644
--- a/net/caif/caif_socket.c
+++ b/net/caif/caif_socket.c
@@ -292,53 +292,42 @@ static void caif_check_flow_release(struct sock *sk)
                         caif_flow_ctrl(sk, CAIF_MODEMCMD_FLOW_ON_REQ);
         }
 }
+
 /*
- * Copied from sock.c:sock_queue_rcv_skb(), and added check that user buffer
- * has sufficient size.
+ * Copied from unix_dgram_recvmsg, but removed credit checks,
+ * changed locking, address handling and added MSG_TRUNC.
  */
-
 static int caif_seqpkt_recvmsg(struct kiocb *iocb, struct socket *sock,
-                                struct msghdr *m, size_t buf_len, int flags)
+                                struct msghdr *m, size_t len, int flags)
 
 {
         struct sock *sk = sock->sk;
         struct sk_buff *skb;
-        int ret = 0;
-        int len;
+        int ret;
+        int copylen;
 
-        if (unlikely(!buf_len))
-                return -EINVAL;
+        ret = -EOPNOTSUPP;
+        if (m->msg_flags&MSG_OOB)
+                goto read_error;
 
         skb = skb_recv_datagram(sk, flags, 0 , &ret);
         if (!skb)
                 goto read_error;
-
-        len = skb->len;
-
-        if (skb && skb->len > buf_len && !(flags & MSG_PEEK)) {
-                len = buf_len;
-                /*
-                 * Push skb back on receive queue if buffer too small.
-                 * This has a built-in race where multi-threaded receive
-                 * may get packet in wrong order, but multiple read does
-                 * not really guarantee ordered delivery anyway.
-                 * Let's optimize for speed without taking locks.
-                 */
-
-                skb_queue_head(&sk->sk_receive_queue, skb);
-                ret = -EMSGSIZE;
-                goto read_error;
+        copylen = skb->len;
+        if (len < copylen) {
+                m->msg_flags |= MSG_TRUNC;
+                copylen = len;
         }
 
-        ret = skb_copy_datagram_iovec(skb, 0, m->msg_iov, len);
+        ret = skb_copy_datagram_iovec(skb, 0, m->msg_iov, copylen);
         if (ret)
-                goto read_error;
+                goto out_free;
 
+        ret = (flags & MSG_TRUNC) ? skb->len : copylen;
+out_free:
         skb_free_datagram(sk, skb);
-
         caif_check_flow_release(sk);
-
-        return len;
+        return ret;
 
 read_error:
         return ret;