[PATCH net v2 4/6] rxrpc: Fix conn-level packet handling to unshare RESPONSE packets

David Howells
2026-04-22T16:15:19Z

The security operations that verify the RESPONSE packets decrypt bits of it
in place - however, the sk_buff may be shared with a packet sniffer, which
would lead to the sniffer seeing an apparently corrupt packet (actually
decrypted).

Fix this by handing a copy of the packet off to the specific security
handler if the packet was cloned.

Fixes: 17926a79320a ("[AF_RXRPC]: Provide secure RxRPC sockets for use by userspace and kernel both")
Closes: https://sashiko.dev/#/patchset/20260408121252.2249051-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Jeffrey Altman <jaltman@auristor.com>
cc: Eric Dumazet <edumazet@google.com>
cc: "David S. Miller" <davem@davemloft.net>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: Simon Horman <horms@kernel.org>
cc: linux-afs@lists.infradead.org
cc: netdev@vger.kernel.org
cc: stable@kernel.org
---
net/rxrpc/conn_event.c | 29 ++++++++++++++++++++++++++++-
1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/net/rxrpc/conn_event.c b/net/rxrpc/conn_event.c
index 9a41ec708aeb..aee977291d90 100644
--- a/net/rxrpc/conn_event.c
+++ b/net/rxrpc/conn_event.c
@@ -240,6 +240,33 @@ static void rxrpc_call_is_secure(struct rxrpc_call *call)
rxrpc_notify_socket(call);
}

+static int rxrpc_verify_response(struct rxrpc_connection *conn,
+ struct sk_buff *skb)
+{
+ int ret;
+
+ if (skb_cloned(skb)) {
+ /* Copy the packet if shared so that we can do in-place
+ * decryption.
+ */
+ struct sk_buff *nskb = skb_copy(skb, GFP_NOFS);
+
+ if (nskb) {
+ rxrpc_new_skb(nskb, rxrpc_skb_new_unshared);
+ ret = conn->security->verify_response(conn, nskb);
+ rxrpc_free_skb(nskb, rxrpc_skb_put_response_copy);
+ } else {
+ /* OOM - Drop the packet. */
+ rxrpc_see_skb(skb, rxrpc_skb_see_unshare_nomem);
+ ret = -ENOMEM;
+ }
+ } else {
+ ret = conn->security->verify_response(conn, skb);
+ }
+
+ return ret;
+}
+
/*
* connection-level Rx packet processor
*/
@@ -270,7 +297,7 @@ static int rxrpc_process_event(struct rxrpc_connection *conn,
}
spin_unlock_irq(&conn->state_lock);

- ret = conn->security->verify_response(conn, skb);
+ ret = rxrpc_verify_response(conn, skb);
if (ret < 0)
return ret;