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 CC9E1C433EF for ; Thu, 16 Dec 2021 17:13:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240054AbhLPRNh (ORCPT ); Thu, 16 Dec 2021 12:13:37 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55696 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240027AbhLPRNd (ORCPT ); Thu, 16 Dec 2021 12:13:33 -0500 Received: from mail-wm1-x332.google.com (mail-wm1-x332.google.com [IPv6:2a00:1450:4864:20::332]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 51B39C061746 for ; Thu, 16 Dec 2021 09:13:33 -0800 (PST) Received: by mail-wm1-x332.google.com with SMTP id o19-20020a1c7513000000b0033a93202467so18535611wmc.2 for ; Thu, 16 Dec 2021 09:13:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to; bh=OMjRsNGHZ2I2ihwsYkZ5ZKcHaWtZzDIKJ4TLgD8hE9U=; b=Dfm60GMi3mu5YKNhQckxceX+apMWSCbYXmdws8hjmeJ8qUUws5F1vYtuAGTNbX1m9E eHHp4I/6dHxFYsJKi+Sou/aAxTCMkqnAJcny+VLO9OMQSSlSqnn/kKX3ND9gBYIsCmFB gWxskOoSgY++PUDvKkaPrI9Uy8MPfNPFuhr8ikuIR8Um+NezmvQtvPGfOD+7Jji+2XO6 Ed+fWbkm7a9D8rc3TE5OiD1h8o9pki3kIWmRIWj5Wn1qmQ59uTAG3ycCLZsp2WmEHJCq AnRsXIpwC0HrQL/GPNmyZQb3ws/nuhEG5TLPxgEXEoYypOOUoha5miRlkRPYjhRrr668 gDqQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=OMjRsNGHZ2I2ihwsYkZ5ZKcHaWtZzDIKJ4TLgD8hE9U=; b=DdrKtsxYt478IqCluRq0RpK7VgDN1SBwHFqId+ZVUEYWKQp+QL0Bvgr/WeciAJaspr RR+Odo+wRA+xDARkqSY9T6+u+8uXosqagnqUxpYaBzjZ6RlZjWFw4RqYJqFhc3dAseDH nlBphVyKajledxva9t47wLJoOxqVD8lIQXh8wopJ0/BOokdMV6Zg/Ev2dFD3O0RJMTPc bHZd04X4rLIHrSiogaGwDR+JVWa7AKIRbru0YGSU0OizlOznpAIarmL6mhbnZ2PSsTgP kJtByEMrYqpCv6bLpHPdEa4xDR3We1/FppA4m9K3sD/ULvVSA8Jfzn0jZikr7TYulX6B Q1mg== X-Gm-Message-State: AOAM531wVMwpE19MhezSXbbidwW8A911BcIjEjgAJxzYXBOfaWG5hlRK iLgTM/Jgyk4y4/2zogc251QaxKG7fBG3BQ== X-Google-Smtp-Source: ABdhPJyxcRuoYfy781SO2sacN5s1W1mYRSYnrQQkbdwrTCVCNwzb/LHSqskPVNDiQprPQeewyhF57g== X-Received: by 2002:a1c:35c2:: with SMTP id c185mr6013201wma.29.1639674811864; Thu, 16 Dec 2021 09:13:31 -0800 (PST) Received: from google.com ([2.31.167.18]) by smtp.gmail.com with ESMTPSA id z15sm5058513wrr.65.2021.12.16.09.13.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Dec 2021 09:13:31 -0800 (PST) Date: Thu, 16 Dec 2021 17:13:19 +0000 From: Lee Jones To: Xin Long Cc: Jakub Kicinski , LKML , Vlad Yasevich , Neil Horman , Marcelo Ricardo Leitner , "David S. Miller" , lksctp developers , "H.P. Yarroll" , Karl Knutson , Jon Grimm , Xingang Guo , Hui Huang , Sridhar Samudrala , Daisy Chang , Ryan Layer , Kevin Gao , network dev Subject: Re: [RESEND 2/2] sctp: hold cached endpoints to prevent possible UAF Message-ID: References: <20211214215732.1507504-1-lee.jones@linaro.org> <20211214215732.1507504-2-lee.jones@linaro.org> <20211215174818.65f3af5e@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, 16 Dec 2021, Xin Long wrote: > On Thu, Dec 16, 2021 at 11:39 AM Lee Jones wrote: > > > > On Thu, 16 Dec 2021, Xin Long wrote: > > > > > On Wed, Dec 15, 2021 at 8:48 PM Jakub Kicinski wrote: > > > > > > > > On Tue, 14 Dec 2021 21:57:32 +0000 Lee Jones wrote: > > > > > The cause of the resultant dump_stack() reported below is a > > > > > dereference of a freed pointer to 'struct sctp_endpoint' in > > > > > sctp_sock_dump(). > > > > > > > > > > This race condition occurs when a transport is cached into its > > > > > associated hash table followed by an endpoint/sock migration to a new > > > > > association in sctp_assoc_migrate() prior to their subsequent use in > > > > > sctp_diag_dump() which uses sctp_for_each_transport() to walk the hash > > > > > table calling into sctp_sock_dump() where the dereference occurs. > > > > > in sctp_sock_dump(): > > > struct sock *sk = ep->base.sk; > > > ... <--[1] > > > lock_sock(sk); > > > > > > Do you mean in [1], the sk is peeled off and gets freed elsewhere? > > > > 'ep' and 'sk' are both switched out for new ones in sctp_sock_migrate(). > > > > > if that's true, it's still late to do sock_hold(sk) in your this patch. > > > > No, that's not right. > > > > The schedule happens *inside* the lock_sock() call. > Sorry, I don't follow this. > We can't expect when the schedule happens, why do you think this > can never be scheduled before the lock_sock() call? True, but I've had this running for hours and it hasn't reproduced. Without this patch, I can reproduce this in around 2 seconds. The C-repro for this is pretty intense! If you want to be *sure* that a schedule will never happen, we can take a reference directly with: ep = sctp_endpoint_hold(tsp->asoc->ep); sk = sock_hold(ep->base.sk); Which was my original plan before I soak tested this submitted patch for hours without any sign of reproducing the issue. > If the sock is peeled off or is being freed, we shouldn't dump this sock, > and it's better to skip it. I guess we can do that too. Are you suggesting sctp_sock_migrate() as the call site? -- Lee Jones [李琼斯] Senior Technical Lead - Developer Services Linaro.org │ Open source software for Arm SoCs Follow Linaro: Facebook | Twitter | Blog