From: Juergen Gross Date: Fri, 6 Nov 2026 13:07:52 +0100 Subject: [PATCH] xen-netback: Fix UAF when reading statistics data The network statistic data in the driver is protected by RCU. Unfortunately when tearing down the queues after an error during connecting to the frontend (e.g. due to illegal Xenstore data filled in by the guest), the statistic data is being freed without synchronizing the RCU state. In case the data is being read via sysfs in this phase, access to already freed memory or memory being in new use is possible. Fix that by calling synchronize_net() before freeing the queue data. This is XSA-526 / CVE-2026-100080 Fixes: b17075d5c198 ("xen-netback: fix race condition on XenBus disconnect") Reported-by: Yehyeong Lee Signed-off-by: Juergen Gross --- drivers/net/xen-netback/xenbus.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c index e020f44ac2c7..c1034d8f6bf0 100644 --- a/drivers/net/xen-netback/xenbus.c +++ b/drivers/net/xen-netback/xenbus.c @@ -837,6 +837,7 @@ static void connect(struct backend_info *be) err: if (be->vif->num_queues > 0) xenvif_disconnect_data(be->vif); /* Clean up existing queues */ + synchronize_net(); for (queue_index = 0; queue_index < be->vif->num_queues; ++queue_index) xenvif_deinit_queue(&be->vif->queues[queue_index]); vfree(be->vif->queues); -- 2.56.0