Re: [PATCH net v4] netrom: linearize and validate lengths in nr_rx_frame()

[Bernard f6bvp <bernard.f6bvp@gmail.com>]

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Hi,

There was also an additional tab in line 14...

Here is well formated patch I applied after fixing it for my own use.

NetRom is performing fine.

Thanks,

Bernard

Le 09/09/2025 à 02:43, Jakub Kicinski a écrit :
> On Sun, 7 Sep 2025 16:32:03 +0200 Bernard Pidoux wrote:
>> While applying netrom PATCH net v4
>> patch says that
>> it is malformed on line 12.
> 
> FWIW the version I received is completely mangled. There's a leading
> space before each +. You can try B4 relay if your mail server is giving
> you grief.

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diff --git a/net/netrom/af_netrom.c b/net/netrom/af_netrom.c
index 3331669..f0660dd 100644
--- a/net/netrom/af_netrom.c
+++ b/net/netrom/af_netrom.c
@@ -885,6 +885,11 @@ int nr_rx_frame(struct sk_buff *skb, struct net_device *dev)
 	 *	skb->data points to the netrom frame start
 	 */
 
+	if (skb_linearize(skb))
+		return 0;
+	if (skb->len < NR_NETWORK_LEN + NR_TRANSPORT_LEN)
+		return 0;
+
 	src  = (ax25_address *)(skb->data + 0);
 	dest = (ax25_address *)(skb->data + 7);
 
@@ -927,6 +932,11 @@ int nr_rx_frame(struct sk_buff *skb, struct net_device *dev)
 	}
 
 	if (sk != NULL) {
+		if (frametype == NR_CONNACK &&
+		    skb->len < NR_NETWORK_LEN + NR_TRANSPORT_LEN + 1) {
+			sock_put(sk);
+			return 0;
+		}
 		bh_lock_sock(sk);
 		skb_reset_transport_header(skb);
 
@@ -961,10 +971,14 @@ int nr_rx_frame(struct sk_buff *skb, struct net_device *dev)
 		return 0;
 	}
 
-	sk = nr_find_listener(dest);
+	/* Need window (byte 20) and user address (bytes 21-27) */
+	if (skb->len < NR_NETWORK_LEN + NR_TRANSPORT_LEN + 1 + AX25_ADDR_LEN)
+		return 0;
 
 	user = (ax25_address *)(skb->data + 21);
 
+	sk = nr_find_listener(dest);
+
 	if (sk == NULL || sk_acceptq_is_full(sk) ||
 	    (make = nr_make_new(sk)) == NULL) {
 		nr_transmit_refusal(skb, 0);