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: 248f219cb8bc ("rxrpc: Rewrite the data and ack handling code")
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeffrey Altman <jaltman@auristor.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Junvyyang, Tencent Zhuque Lab <zhuque@tencent.com>
cc: LePremierHomme <kwqcheii@proton.me>
cc: Linus Torvalds <torvalds@linux-foundation.org>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: "David S. Miller" <davem@davemloft.net>
cc: Eric Dumazet <edumazet@google.com>
cc: Simon Horman <horms@kernel.org>
cc: linux-afs@lists.infradead.org
cc: netdev@vger.kernel.org
cc: stable@vger.kernel.org
---
 net/rxrpc/output.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/rxrpc/output.c b/net/rxrpc/output.c
index ef7b3096c95e..17c33b5cf7dd 100644
--- a/net/rxrpc/output.c
+++ b/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;