Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S942386AbcJSO3d (ORCPT ); Wed, 19 Oct 2016 10:29:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51018 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S942295AbcJSO3a (ORCPT ); Wed, 19 Oct 2016 10:29:30 -0400 From: Vitaly Kuznetsov To: netdev@vger.kernel.org Cc: Stephen Hemminger , devel@linuxdriverproject.org, linux-kernel@vger.kernel.org, "K. Y. Srinivasan" , Haiyang Zhang Subject: [PATCH net-next] hv_netvsc: fix a race between netvsc_send() and netvsc_init_buf() Date: Wed, 19 Oct 2016 15:53:01 +0200 Message-Id: <1476885181-3456-1-git-send-email-vkuznets@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Wed, 19 Oct 2016 13:53:04 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1638 Lines: 40 Fix in commit 880988348270 ("hv_netvsc: set nvdev link after populating chn_table") turns out to be incomplete. A crash in netvsc_get_next_send_section() is observed on mtu change when the device is under load. The race I identified is: if we get to netvsc_send() after we set net_device_ctx->nvdev link in netvsc_device_add() but before we finish netvsc_connect_vsp()->netvsc_init_buf() send_section_map is not allocated and we crash. Unfortunately we can't set net_device_ctx->nvdev link after the netvsc_init_buf() call as during the negotiation we need to receive packets and on the receive path we check for it. It would probably be possible to split nvdev into a pair of nvdev_in and nvdev_out links and check them accordingly in get_outbound_net_device()/ get_inbound_net_device() but this looks like an overkill. Check that send_section_map is allocated in netvsc_send(). Signed-off-by: Vitaly Kuznetsov --- drivers/net/hyperv/netvsc.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c index 720b5fa..e2bfaac 100644 --- a/drivers/net/hyperv/netvsc.c +++ b/drivers/net/hyperv/netvsc.c @@ -888,6 +888,13 @@ int netvsc_send(struct hv_device *device, if (!net_device) return -ENODEV; + /* We may race with netvsc_connect_vsp()/netvsc_init_buf() and get + * here before the negotiation with the host is finished and + * send_section_map may not be allocated yet. + */ + if (!net_device->send_section_map) + return -EAGAIN; + out_channel = net_device->chn_table[q_idx]; packet->send_buf_index = NETVSC_INVALID_INDEX; -- 2.7.4