From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DC8F4C43603 for ; Thu, 5 Dec 2019 00:50:42 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A1E6B21823 for ; Thu, 5 Dec 2019 00:50:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="YswFjRnN" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A1E6B21823 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 504D86B0D85; Wed, 4 Dec 2019 19:50:42 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 4DC1B6B0D86; Wed, 4 Dec 2019 19:50:42 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 418BB6B0D87; Wed, 4 Dec 2019 19:50:42 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0072.hostedemail.com [216.40.44.72]) by kanga.kvack.org (Postfix) with ESMTP id 2C3306B0D85 for ; Wed, 4 Dec 2019 19:50:42 -0500 (EST) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id DA46980750A5 for ; Thu, 5 Dec 2019 00:50:41 +0000 (UTC) X-FDA: 76229257482.10.home88_609380c6ac03 X-HE-Tag: home88_609380c6ac03 X-Filterd-Recvd-Size: 4972 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf27.hostedemail.com (Postfix) with ESMTP for ; Thu, 5 Dec 2019 00:50:41 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E09112077B; Thu, 5 Dec 2019 00:50:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1575507040; bh=9pSMN0TfD7qFSgSKGHRbL9NA01lnKCza1z6w6a6WEUA=; h=Date:From:To:Subject:In-Reply-To:From; b=YswFjRnN6+EKR5qeuciNvdM6S6RetO2mI1TZsZJDrh9uAmgelr7zmCYVwPjVnF8GC BbdNFHFpUVnfuFkhbQ8QQTwJOot+6ZZCHky2Rz0r3eTKFx/Jmss5cVMVZXdxwfJX8z TZm2BjQnTz1a5hb//EoWXUd6q0FAzV5eKvUp93Vc= Date: Wed, 04 Dec 2019 16:50:39 -0800 From: Andrew Morton To: adobriyan@gmail.com, akpm@linux-foundation.org, anna.schumaker@netapp.com, arjan@linux.intel.com, bfields@fieldses.org, chuck.lever@oracle.com, davem@davemloft.net, jlayton@kernel.org, linux-mm@kvack.org, luto@kernel.org, mingo@kernel.org, mm-commits@vger.kernel.org, Nadia.Derbey@bull.net, nixiaoming@huawei.com, paulmck@kernel.org, semen.protsenko@linaro.org, stern@rowland.harvard.edu, tglx@linutronix.de, torvalds@linux-foundation.org, trond.myklebust@hammerspace.com, viresh.kumar@linaro.org, vvs@virtuozzo.com, yuehaibing@huawei.com Subject: [patch 19/86] kernel/notifier.c: intercept duplicate registrations to avoid infinite loops Message-ID: <20191205005039.RKFvLxRvH%akpm@linux-foundation.org> In-Reply-To: <20191204164858.fe4ed8886e34ad9f3b34ea00@linux-foundation.org> User-Agent: s-nail v14.8.16 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Xiaoming Ni Subject: kernel/notifier.c: intercept duplicate registrations to avoid infinite loops Registering the same notifier to a hook repeatedly can cause the hook list to form a ring or lose other members of the list. case1: An infinite loop in notifier_chain_register() can cause soft lockup atomic_notifier_chain_register(&test_notifier_list, &test1); atomic_notifier_chain_register(&test_notifier_list, &test1); atomic_notifier_chain_register(&test_notifier_list, &test2); case2: An infinite loop in notifier_chain_register() can cause soft lockup atomic_notifier_chain_register(&test_notifier_list, &test1); atomic_notifier_chain_register(&test_notifier_list, &test1); atomic_notifier_call_chain(&test_notifier_list, 0, NULL); case3: lose other hook test2 atomic_notifier_chain_register(&test_notifier_list, &test1); atomic_notifier_chain_register(&test_notifier_list, &test2); atomic_notifier_chain_register(&test_notifier_list, &test1); case4: Unregister returns 0, but the hook is still in the linked list, and it is not really registered. If you call notifier_call_chain after ko is unloaded, it will trigger oops. If the system is configured with softlockup_panic and the same hook is repeatedly registered on the panic_notifier_list, it will cause a loop panic. Add a check in notifier_chain_register(), Intercepting duplicate registrations to avoid infinite loops Link: http://lkml.kernel.org/r/1568861888-34045-2-git-send-email-nixiaoming@huawei.com Signed-off-by: Xiaoming Ni Reviewed-by: Vasily Averin Reviewed-by: Andrew Morton Cc: Alexey Dobriyan Cc: Anna Schumaker Cc: Arjan van de Ven Cc: J. Bruce Fields Cc: Chuck Lever Cc: David S. Miller Cc: Jeff Layton Cc: Andy Lutomirski Cc: Ingo Molnar Cc: Nadia Derbey Cc: "Paul E. McKenney" Cc: Sam Protsenko Cc: Alan Stern Cc: Thomas Gleixner Cc: Trond Myklebust Cc: Viresh Kumar Cc: Xiaoming Ni Cc: YueHaibing Signed-off-by: Andrew Morton --- kernel/notifier.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/kernel/notifier.c~kernel-notifierc-intercepting-duplicate-registrations-to-avoid-infinite-loops +++ a/kernel/notifier.c @@ -23,7 +23,10 @@ static int notifier_chain_register(struc struct notifier_block *n) { while ((*nl) != NULL) { - WARN_ONCE(((*nl) == n), "double register detected"); + if (unlikely((*nl) == n)) { + WARN(1, "double register detected"); + return 0; + } if (n->priority > (*nl)->priority) break; nl = &((*nl)->next); _