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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C8D2FC54EE9 for ; Thu, 8 Sep 2022 21:20:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229707AbiIHVUJ (ORCPT ); Thu, 8 Sep 2022 17:20:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42974 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229713AbiIHVUD (ORCPT ); Thu, 8 Sep 2022 17:20:03 -0400 Received: from mail-il1-x12c.google.com (mail-il1-x12c.google.com [IPv6:2607:f8b0:4864:20::12c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C1A6372B7A for ; Thu, 8 Sep 2022 14:19:58 -0700 (PDT) Received: by mail-il1-x12c.google.com with SMTP id l6so9944656ilk.13 for ; Thu, 08 Sep 2022 14:19:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20210112.gappssmtp.com; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date; bh=W7BcbWZFGTPcuazjR/BNB1mMCuppDikRbnJ5pIj0+mw=; b=zct8VMknboCOyI370q4FuKwfLFJDP4DKP7Dzw3NgHOsjWpbiPGC6UL6bSWKmh5m+uf d7sv03n80KdoYX4wIyRG1tCeUA6QWtjYkFZvOt6Ymk8pkCe2XcQfgU+/SLKk8VKc5Bdh 3+gsO01fxWrEPpPpPTziAipX4dfPx8cHTGLhTaPMczzQ476Z3EYEnIU00hNWbE00lMJV qFt8mTvTRDvHD9CQploYoXv3UqnB+7vXDyWAREeVKz54I4fpI5vXou3ltLVWiQN85vKy GseviYdFNem3vIOVxEWzaHseaNNkPPUQlG81PP8RJJGRW8HLRJYvw++AB64hQtcYJQJi NgTA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date; bh=W7BcbWZFGTPcuazjR/BNB1mMCuppDikRbnJ5pIj0+mw=; b=OHIw+5zitywKX8YWUVc3Ks6+gFoJr543xU8UdN1cvsojzFUQjO1sCD/6gHxhf9L7oK igqSaEv1FS00yWLAOzsQVbbBQllb3VzbSgyhbVOmQFw52rD8JdQhBKUfkuWsaSucdyiI 6LquabkSMXqYIpYGOxqupZX0SnoDObiBEwBphsTN7YpOQA25Rf9F8XFKf10Bi2Ks77O/ qo6cSnSM56AqffTzgs2A9rc02D0Y3+oBXQIkYiZ3K3RLoe6GTzc2bijcLoLuDJyPfKAy zbImaO7SFlr9/x/5fVtP5gbqGEJR2LV2ghJDagywwj3d/UKrt/Pam1sPP1eH1DLMyJx+ tFVw== X-Gm-Message-State: ACgBeo2zwX3+/bZSgbOQWT7HJY2sD6xIgUpENis2WhOOg7HvgdtHESMF B/4Ue7JRAcCWJ2rCeLHxzZl/LQ== X-Google-Smtp-Source: AA6agR6xEtGucm4Kbo1Ls2x0QBrOK545GLZ5CdZfNi/eKMOiPoK+6vDdl9JG8UncSe+4M0wnAKi82w== X-Received: by 2002:a05:6e02:1a45:b0:2f0:4b56:e5f3 with SMTP id u5-20020a056e021a4500b002f04b56e5f3mr2873087ilv.76.1662671997011; Thu, 08 Sep 2022 14:19:57 -0700 (PDT) Received: from [192.168.1.94] ([207.135.234.126]) by smtp.gmail.com with ESMTPSA id q204-20020a6b2ad5000000b00685a7cccd2csm1440371ioq.45.2022.09.08.14.19.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 08 Sep 2022 14:19:56 -0700 (PDT) Message-ID: <995450c5-a4f2-d2d1-8a44-569726eb7231@kernel.dk> Date: Thu, 8 Sep 2022 15:19:55 -0600 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:102.0) Gecko/20100101 Thunderbird/102.2.1 Subject: Re: [PATCH] relay: replay_file_open(): NULL ptr deref in CPU hotplugs Content-Language: en-US To: "Yichun Zhang (agentzh)" , linux-fsdevel@vger.kernel.org Cc: Colin Ian King , Andrew Morton , linux-kernel@vger.kernel.org References: <20220908211731.11534-1-yichun@openresty.com> From: Jens Axboe In-Reply-To: <20220908211731.11534-1-yichun@openresty.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/8/22 3:17 PM, Yichun Zhang (agentzh) wrote: > CPU hotplug may introduce race conditions. We reproduced kernel panics > due to this NULL ptr deref error when doing frequent random CPU hotplugs > in a KVM guest. > > Signed-off-by: Yichun Zhang (agentzh) > --- > kernel/relay.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/kernel/relay.c b/kernel/relay.c > index 6a611e779e95..2db69fd527d1 100644 > --- a/kernel/relay.c > +++ b/kernel/relay.c > @@ -816,6 +816,9 @@ EXPORT_SYMBOL_GPL(relay_flush); > static int relay_file_open(struct inode *inode, struct file *filp) > { > struct rchan_buf *buf = inode->i_private; > + if (unlikely(buf == NULL)) > + return -ENOENT; > + > kref_get(&buf->kref); > filp->private_data = buf; If it can go away before open is called, what prevents it from going away after that check but before kref_get() is called? -- Jens Axboe