From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELsp6aL/EZcrqEbPiueYqNbHafN+Gb+dbmNBD4ZcUssgQt2z85SgszBGCLAnT8YGmp5uLm5L ARC-Seal: i=1; a=rsa-sha256; t=1520451943; cv=none; d=google.com; s=arc-20160816; b=uBpibjP6nV/4EWPu5/k82xFhIC3BNqXvyEYpVD+bUh9C5E8WkBfgPjfTM17X8UAo5G VtY51bvYvSalCgpHE3YEmG3jfUORe/pJEqt2af/K+t9n7y4mX1asPH9M2/qfew9MyL24 gMSC50s+JT39rfgORz7ijLrWfd1Z6JD/KzYzfyueolZki5eURNc9aMNH+1UFAN24Aa/a HfpXE+v9a5ZNoiGVa5cXHTwtzjUTDzsd3hyr6hYhcEcthk8panjWShhpbT9BWQ0bdRJA xzbezhHtj5jK8sz7ATuu6iWFOZ7Dlxb2ThPHQKO5//bJcuc7X9GusjSoekKYByHQ8U+P Q+5A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=Scts/hJbY42HoF0zRz6TrXjmzzwhpfANbK5NY/nDezw=; b=WJwadjYJE4kCnR1YfYtQArIyCVaRMLJAiYbN58PdJ51bMOZ7RaOuV8NuhzHw9mDRcX HxkHxCFdkM8sb5jHdM8TXs0b+H8KFQDstGTlgrwCHR1ujfJbMcf0hVjylQylfbsLezXT mUFPAIHOz3D8bIDBiKX4C5glWQzs+GxshXwJVgXXExLXvKjYs3Er1A7W38WyWfhw08Ch DV0Oj171fJyJ1MeCz2xstSERLTzLuXfrbbQGA+yjMGUqrHl8/lFDsc3QGpez7pqaQPkY K7mAGO877Wj9ScqetNFpjDtsX/qWgrOCtohBnkN3LlfTta7lW46LntC5gV/CC5usudWx tZHQ== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 185.236.200.248 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 185.236.200.248 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jakub Kicinski , "David S. Miller" Subject: [PATCH 4.14 040/110] net: fix race on decreasing number of TX queues Date: Wed, 7 Mar 2018 11:38:23 -0800 Message-Id: <20180307191044.878257226@linuxfoundation.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180307191039.748351103@linuxfoundation.org> References: <20180307191039.748351103@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1594309127138862131?= X-GMAIL-MSGID: =?utf-8?q?1594309416860689969?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jakub Kicinski [ Upstream commit ac5b70198adc25c73fba28de4f78adcee8f6be0b ] netif_set_real_num_tx_queues() can be called when netdev is up. That usually happens when user requests change of number of channels/rings with ethtool -L. The procedure for changing the number of queues involves resetting the qdiscs and setting dev->num_tx_queues to the new value. When the new value is lower than the old one, extra care has to be taken to ensure ordering of accesses to the number of queues vs qdisc reset. Currently the queues are reset before new dev->num_tx_queues is assigned, leaving a window of time where packets can be enqueued onto the queues going down, leading to a likely crash in the drivers, since most drivers don't check if TX skbs are assigned to an active queue. Fixes: e6484930d7c7 ("net: allocate tx queues in register_netdevice") Signed-off-by: Jakub Kicinski Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/core/dev.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) --- a/net/core/dev.c +++ b/net/core/dev.c @@ -2343,8 +2343,11 @@ EXPORT_SYMBOL(netdev_set_num_tc); */ int netif_set_real_num_tx_queues(struct net_device *dev, unsigned int txq) { + bool disabling; int rc; + disabling = txq < dev->real_num_tx_queues; + if (txq < 1 || txq > dev->num_tx_queues) return -EINVAL; @@ -2360,15 +2363,19 @@ int netif_set_real_num_tx_queues(struct if (dev->num_tc) netif_setup_tc(dev, txq); - if (txq < dev->real_num_tx_queues) { + dev->real_num_tx_queues = txq; + + if (disabling) { + synchronize_net(); qdisc_reset_all_tx_gt(dev, txq); #ifdef CONFIG_XPS netif_reset_xps_queues_gt(dev, txq); #endif } + } else { + dev->real_num_tx_queues = txq; } - dev->real_num_tx_queues = txq; return 0; } EXPORT_SYMBOL(netif_set_real_num_tx_queues);