From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julian Wiedmann Subject: [PATCH net 2/5] s390/qeth: fix race when setting MAC address Date: Fri, 29 Jun 2018 19:45:51 +0200 Message-ID: <20180629174554.53718-3-jwi@linux.ibm.com> References: <20180629174554.53718-1-jwi@linux.ibm.com> Cc: , , Martin Schwidefsky , Heiko Carstens , Stefan Raspl , Ursula Braun , Julian Wiedmann To: David Miller Return-path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:39162 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754453AbeF2RqJ (ORCPT ); Fri, 29 Jun 2018 13:46:09 -0400 Received: from pps.filterd (m0098409.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w5THiDhw089432 for ; Fri, 29 Jun 2018 13:46:09 -0400 Received: from e06smtp04.uk.ibm.com (e06smtp04.uk.ibm.com [195.75.94.100]) by mx0a-001b2d01.pphosted.com with ESMTP id 2jwrrusqbg-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Fri, 29 Jun 2018 13:46:08 -0400 Received: from localhost by e06smtp04.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 29 Jun 2018 18:46:06 +0100 In-Reply-To: <20180629174554.53718-1-jwi@linux.ibm.com> Sender: netdev-owner@vger.kernel.org List-ID: When qeth_l2_set_mac_address() finds the card in a non-reachable state, it merely copies the new MAC address into dev->dev_addr so that __qeth_l2_set_online() can later register it with the HW. But __qeth_l2_set_online() may very well be running concurrently, so we can't trust the card state without appropriate locking: If the online sequence is past the point where it registers dev->dev_addr (but not yet in SOFTSETUP state), any address change needs to be properly programmed into the HW. Otherwise the netdevice ends up with a different MAC address than what's set in the HW, and inbound traffic is not forwarded as expected. This is most likely to occur for OSD in LPAR, where commit 21b1702af12e ("s390/qeth: improve fallback to random MAC address") now triggers eg. systemd to immediately change the MAC when the netdevice is registered with a NET_ADDR_RANDOM address. Fixes: bcacfcbc82b4 ("s390/qeth: fix MAC address update sequence") Signed-off-by: Julian Wiedmann --- drivers/s390/net/qeth_l2_main.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/drivers/s390/net/qeth_l2_main.c b/drivers/s390/net/qeth_l2_main.c index a7cb37da6a21..7daf125dae76 100644 --- a/drivers/s390/net/qeth_l2_main.c +++ b/drivers/s390/net/qeth_l2_main.c @@ -501,27 +501,34 @@ static int qeth_l2_set_mac_address(struct net_device *dev, void *p) return -ERESTARTSYS; } + /* avoid racing against concurrent state change: */ + if (!mutex_trylock(&card->conf_mutex)) + return -EAGAIN; + if (!qeth_card_hw_is_reachable(card)) { ether_addr_copy(dev->dev_addr, addr->sa_data); - return 0; + goto out_unlock; } /* don't register the same address twice */ if (ether_addr_equal_64bits(dev->dev_addr, addr->sa_data) && (card->info.mac_bits & QETH_LAYER2_MAC_REGISTERED)) - return 0; + goto out_unlock; /* add the new address, switch over, drop the old */ rc = qeth_l2_send_setmac(card, addr->sa_data); if (rc) - return rc; + goto out_unlock; ether_addr_copy(old_addr, dev->dev_addr); ether_addr_copy(dev->dev_addr, addr->sa_data); if (card->info.mac_bits & QETH_LAYER2_MAC_REGISTERED) qeth_l2_remove_mac(card, old_addr); card->info.mac_bits |= QETH_LAYER2_MAC_REGISTERED; - return 0; + +out_unlock: + mutex_unlock(&card->conf_mutex); + return rc; } static void qeth_promisc_to_bridge(struct qeth_card *card) -- 2.16.4