From patchwork Fri Jul 7 10:17:01 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Ziyang Xuan (William)" X-Patchwork-Id: 13304710 X-Patchwork-Delegate: kuba@kernel.org Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DDF9F20E0 for ; Fri, 7 Jul 2023 10:17:11 +0000 (UTC) Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5D98A10B for ; Fri, 7 Jul 2023 03:17:09 -0700 (PDT) Received: from canpemm500006.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Qy8PX1VZfzMqHq; Fri, 7 Jul 2023 18:13:52 +0800 (CST) Received: from localhost.localdomain (10.175.104.82) by canpemm500006.china.huawei.com (7.192.105.130) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.27; Fri, 7 Jul 2023 18:17:06 +0800 From: Ziyang Xuan To: , , , , , , , Subject: [PATCH net] ipv6/addrconf: fix a potential refcount underflow for idev Date: Fri, 7 Jul 2023 18:17:01 +0800 Message-ID: <20230707101701.2474499-1-william.xuanziyang@huawei.com> X-Mailer: git-send-email 2.25.1 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Originating-IP: [10.175.104.82] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To canpemm500006.china.huawei.com (7.192.105.130) X-CFilter-Loop: Reflected X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_MED, RCVD_IN_MSPIKE_H5,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: kuba@kernel.org Now in addrconf_mod_rs_timer(), reference idev depends on whether rs_timer is not pending. Then modify rs_timer timeout. There is a time gap in [1], during which if the pending rs_timer becomes not pending. It will miss to hold idev, but the rs_timer is activated. Thus rs_timer callback function addrconf_rs_timer() will be executed and put idev later without holding idev. A refcount underflow issue for idev can be caused by this. if (!timer_pending(&idev->rs_timer)) in6_dev_hold(idev); <--------------[1] mod_timer(&idev->rs_timer, jiffies + when); Hold idev anyway firstly. Then call mod_timer() for rs_timer, put idev if mod_timer() return 1. This modification takes into account the case where "when" is 0. Fixes: b7b1bfce0bb6 ("ipv6: split duplicate address detection and router solicitation timer") Signed-off-by: Ziyang Xuan --- net/ipv6/addrconf.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index 5479da08ef40..d36e6c5e3081 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -318,9 +318,9 @@ static void addrconf_del_dad_work(struct inet6_ifaddr *ifp) static void addrconf_mod_rs_timer(struct inet6_dev *idev, unsigned long when) { - if (!timer_pending(&idev->rs_timer)) - in6_dev_hold(idev); - mod_timer(&idev->rs_timer, jiffies + when); + in6_dev_hold(idev); + if (mod_timer(&idev->rs_timer, jiffies + when)) + in6_dev_put(idev); } static void addrconf_mod_dad_work(struct inet6_ifaddr *ifp,