From patchwork Mon Nov 15 14:56:00 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lin Ma X-Patchwork-Id: 12619701 X-Patchwork-Delegate: kuba@kernel.org Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 008D8C433EF for ; Mon, 15 Nov 2021 14:56:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DB14A63214 for ; Mon, 15 Nov 2021 14:56:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234996AbhKOO7o (ORCPT ); Mon, 15 Nov 2021 09:59:44 -0500 Received: from mail.zju.edu.cn ([61.164.42.155]:29340 "EHLO zju.edu.cn" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S232314AbhKOO7D (ORCPT ); Mon, 15 Nov 2021 09:59:03 -0500 Received: from localhost.localdomain (unknown [222.205.2.245]) by mail-app3 (Coremail) with SMTP id cC_KCgCX6G0AdZJhnaEtCA--.51040S4; Mon, 15 Nov 2021 22:56:00 +0800 (CST) From: Lin Ma To: netdev@vger.kernel.org Cc: krzysztof.kozlowski@canonical.com, davem@davemloft.net, kuba@kernel.org, jirislaby@kernel.org, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, Lin Ma Subject: [PATCH v1] NFC: reorganize the functions in nci_request Date: Mon, 15 Nov 2021 22:56:00 +0800 Message-Id: <20211115145600.8320-1-linma@zju.edu.cn> X-Mailer: git-send-email 2.33.1 MIME-Version: 1.0 X-CM-TRANSID: cC_KCgCX6G0AdZJhnaEtCA--.51040S4 X-Coremail-Antispam: 1UD129KBjvJXoW7urWxGw4fJr1rWF1DKF4Durg_yoW8XF1kpa 95KFyayFyxZ3y7Zr40yw18Xw15ZF10ka97Ga4Yyw18Cr9xXwnrtr1UtFW5Xryfu395ZFZx XFy5ta4F9r1UWaUanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvY1xkIjI8I6I8E6xAIw20EY4v20xvaj40_Wr0E3s1l1IIY67AE w4v_Jr0_Jr4l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0rcxSw2x7M28EF7xvwVC0I7IYx2 IY67AKxVWDJVCq3wA2z4x0Y4vE2Ix0cI8IcVCY1x0267AKxVWxJr0_GcWl84ACjcxK6I8E 87Iv67AKxVW0oVCq3wA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_GcCE3s1le2I262IYc4CY6c 8Ij28IcVAaY2xG8wAqx4xG64xvF2IEw4CE5I8CrVC2j2WlYx0E2Ix0cI8IcVAFwI0_Jr0_ Jr4lYx0Ex4A2jsIE14v26r1j6r4UMcvjeVCFs4IE7xkEbVWUJVW8JwACjcxG0xvY0x0EwI xGrwACjI8F5VA0II8E6IAqYI8I648v4I1lc2xSY4AK67AK6ry5MxAIw28IcxkI7VAKI48J MxAIw28IcVCjz48v1sIEY20_GFWkJr1UJwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c 02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_ GFylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7 CjxVAFwI0_Jr0_Gr1lIxAIcVCF04k26cxKx2IYs7xG6r1j6r1xMIIF0xvEx4A2jsIE14v2 6r1j6r4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x0J UmzuXUUUUU= X-CM-SenderInfo: qtrwiiyqvtljo62m3hxhgxhubq/ Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org There is a possible data race as shown below: thread-A in nci_request() | thread-B in nci_close_device() | mutex_lock(&ndev->req_lock); test_bit(NCI_UP, &ndev->flags); | ... | test_and_clear_bit(NCI_UP, &ndev->flags) mutex_lock(&ndev->req_lock); | | This race will allow __nci_request() to be awaked while the device is getting removed. Similar to commit e2cb6b891ad2 ("bluetooth: eliminate the potential race condition when removing the HCI controller"). this patch alters the function sequence in nci_request() to prevent the data races between the nci_close_device(). Signed-off-by: Lin Ma Fixes: 6a2968aaf50c ("NFC: basic NCI protocol implementation") --- net/nfc/nci/core.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/net/nfc/nci/core.c b/net/nfc/nci/core.c index 6fd873aa86be..1dd0269c1a72 100644 --- a/net/nfc/nci/core.c +++ b/net/nfc/nci/core.c @@ -144,12 +144,15 @@ inline int nci_request(struct nci_dev *ndev, { int rc; - if (!test_bit(NCI_UP, &ndev->flags)) - return -ENETDOWN; - /* Serialize all requests */ mutex_lock(&ndev->req_lock); - rc = __nci_request(ndev, req, opt, timeout); + /* check the state after obtaing the lock against any races + * from nci_close_device when the device gets removed. + */ + if (test_bit(NCI_UP, &ndev->flags)) + rc = __nci_request(ndev, req, opt, timeout); + else + rc = -ENETDOWN; mutex_unlock(&ndev->req_lock); return rc;