ax25: zero length frame filtering in AX25

In previous commit 244f46ae6e9e18f6fc0be7d1f49febde4762c34b
was introduced a zero length frame filter for ROSE protocole.
This patch has the same purpose at AX25 frame level for the same
reason. Empty frames have no meaning in AX25 protocole.

Signed-off-by: Bernard Pidoux <f6bvp@amsat.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 0 deletions

diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
index fd9d06f291dc..7da5ebb84e97 100644
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -1435,6 +1435,11 @@ static int ax25_sendmsg(struct kiocb *iocb, struct socket *sock,
         size_t size;
         int lv, err, addr_len = msg->msg_namelen;
 
+        /* AX.25 empty data frame has no meaning : don't send */
+        if (len == 0) {
+                return (0);
+        }
+
         if (msg->msg_flags & ~(MSG_DONTWAIT|MSG_EOR|MSG_CMSG_COMPAT))
                 return -EINVAL;
 
@@ -1634,6 +1639,13 @@ static int ax25_recvmsg(struct kiocb *iocb, struct socket *sock,
         skb_reset_transport_header(skb);
         copied = skb->len;
 
+        /* AX.25 empty data frame has no meaning : ignore it */
+        if (copied == 0) {
+                err = copied;
+                skb_free_datagram(sk, skb);
+                goto out;
+        }
+
         if (copied > size) {
                 copied = size;
                 msg->msg_flags |= MSG_TRUNC;