esp: fix skb leak with espintcp and async crypto

When the TX queue for espintcp is full, esp_output_tail_tcp will
return an error and not free the skb, because with synchronous crypto,
the common xfrm output code will drop the packet for us.

With async crypto (esp_output_done), we need to drop the skb when
esp_output_tail_tcp returns an error.

Fixes: e27cca9 ("xfrm: add espintcp (RFC 8229)")
Signed-off-by: Sabrina Dubroca <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Signed-off-by: Steffen Klassert <[email protected]>

Author: qsn

net/ipv4/esp4.c

@@ -235,10 +235,13 @@ static void esp_output_done(void *data, int err)
 		xfrm_dev_resume(skb);
 	} else {
 		if (!err &&
-		    x->encap && x->encap->encap_type == TCP_ENCAP_ESPINTCP)
-			esp_output_tail_tcp(x, skb);
-		else
+		    x->encap && x->encap->encap_type == TCP_ENCAP_ESPINTCP) {
+			err = esp_output_tail_tcp(x, skb);
+			if (err != -EINPROGRESS)
+				kfree_skb(skb);
+		} else {
 			xfrm_output_resume(skb_to_full_sk(skb), skb, err);
+		}
 	}
 }
 

net/ipv6/esp6.c

@@ -271,10 +271,13 @@ static void esp_output_done(void *data, int err)
 		xfrm_dev_resume(skb);
 	} else {
 		if (!err &&
-		    x->encap && x->encap->encap_type == TCP_ENCAP_ESPINTCP)
-			esp_output_tail_tcp(x, skb);
-		else
+		    x->encap && x->encap->encap_type == TCP_ENCAP_ESPINTCP) {
+			err = esp_output_tail_tcp(x, skb);
+			if (err != -EINPROGRESS)
+				kfree_skb(skb);
+		} else {
 			xfrm_output_resume(skb_to_full_sk(skb), skb, err);
+		}
 	}
 }