xen-netfront: restore __skb_queue_tail() positioning in xennet_get_responses()

commit f63c2c2032c2e3caad9add3b82cc6e91c376fd26 upstream.

The commit referenced below moved the invocation past the "next" label,
without any explanation. In fact this allows misbehaving backends undue
control over the domain the frontend runs in, as earlier detected errors
require the skb to not be freed (it may be retained for later processing
via xennet_move_rx_slot(), or it may simply be unsafe to have it freed).

This is CVE-2022-33743 / XSA-405.

Fixes: 6c5aa6fc4def ("xen networking: add basic XDP support for xen-netfront")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index bae3ad139f061f1070ad94bf65fd62aaa3c14a17..569f3c8e7b756f41ad42cae94e305b2b0c8a78c2 100644 (file)
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1096,8 +1096,10 @@ static int xennet_get_responses(struct netfront_queue *queue,
                        }
                }
                rcu_read_unlock();
-next:
+
                __skb_queue_tail(list, skb);
+
+next:
                if (!(rx->flags & XEN_NETRXF_more_data))
                        break;