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

BugLink: https://bugs.launchpad.net/bugs/1986728
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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 409ee9d97af48b35e99058038fc9a37054c24d18..074dceb1930b3505370dfca140b24f7739fea8d9 100644 (file)
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1094,8 +1094,10 @@ 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;