rxrpc: Fix transmission of an abort in response to an abort

Under some circumstances, such as when a server socket is closing, ABORT
packets will be generated in response to incoming packets.  Unfortunately,
this also may include generating aborts in response to incoming aborts -
which may cause a cycle.  It appears this may be made possible by giving
the client a multicast address.

Fix this such that rxrpc_reject_packet() will refuse to generate aborts in
response to aborts.

Fixes: 248f219 ("rxrpc: Rewrite the data and ack handling code")
Signed-off-by: David Howells <[email protected]>
Reviewed-by: Jeffrey Altman <[email protected]>
cc: Marc Dionne <[email protected]>
cc: Junvyyang, Tencent Zhuque Lab <[email protected]>
cc: LePremierHomme <[email protected]>
cc: Linus Torvalds <[email protected]>
cc: Simon Horman <[email protected]>
cc: [email protected]
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: dhowells

net/rxrpc/output.c

@@ -814,6 +814,9 @@ void rxrpc_reject_packet(struct rxrpc_local *local, struct sk_buff *skb)
 	__be32 code;
 	int ret, ioc;
 
+	if (sp->hdr.type == RXRPC_PACKET_TYPE_ABORT)
+		return; /* Never abort an abort. */
+
 	rxrpc_see_skb(skb, rxrpc_skb_see_reject);
 
 	iov[0].iov_base = &whdr;