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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 E0C76C433E0 for ; Mon, 25 May 2020 09:12:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B7CDB2073B for ; Mon, 25 May 2020 09:12:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="PFmfYN4Y" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731228AbgEYJMB (ORCPT ); Mon, 25 May 2020 05:12:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52906 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725809AbgEYJMA (ORCPT ); Mon, 25 May 2020 05:12:00 -0400 Received: from mail-pl1-x642.google.com (mail-pl1-x642.google.com [IPv6:2607:f8b0:4864:20::642]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 79178C061A0E for ; Mon, 25 May 2020 02:12:00 -0700 (PDT) Received: by mail-pl1-x642.google.com with SMTP id x10so7274173plr.4 for ; Mon, 25 May 2020 02:12:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:date:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=/OWDsHDL70sQccYbo8Luw6/UtlKJg70Rl3vnaAOycYw=; b=PFmfYN4YmPTzCr9oNgJE8uG4Yj2KzMbpmILiU0eap+q1Ezba8aE9u2lAn34ZF+/R9/ Ex7W6dsTHbBOZeC0jLET4tJ7DoOQPqpPYqQ7mIjoNmT7WLz7bJfJdJmG/1h1mFe5R6tm NII+xiE0yerCBIqrGI29tCFQqE8ckF/wN/MnbXSMhciV4L6qXEXhhp8aMNVIXVPAJtwa nCQBkOT6sP3nVPbo1lQ8MYbzRDm8KJ7WeY+3mlEEJDma3msEaPXeLw8yLGcaZxVIwV0y lb5IPeAFDW2FzsMTmoSZvWsjtjWGLu+CWWmKY0A3AxQPtpo8Y8SkjGOcQiNeQwUWZt+1 Wn+w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:date:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=/OWDsHDL70sQccYbo8Luw6/UtlKJg70Rl3vnaAOycYw=; b=DW9jdv28G65jRb8qFQBYHx14lRXKimji5+boM02I422gXhEge7l5pRmHOuq6FJ2xha XlJvVkBQbzrVrxc2VmgNC1Pphut5SIPhvtRHWAsQ8zf+1KZmphJXkMtaexHuyeobgsI3 PW25nagh/nC/e6T+IA1hnYaXB8NbqtmcYVLVMyqXWVuKCYUCWYJJL8t3Cqsm9RBvgQOq OM4HC89FISlaOJE/SGvcicqbb4kgglYX52XuEWotszga+jYiAo0HTScZIwBBqqsWs1TU IhsEZjB5dueoDDwQgrSz6nPUXbTu7OJ43Pz+q/K4coG1jn73RLe+YNsG3p1XWOZ9HPnm Hudg== X-Gm-Message-State: AOAM533O0oHiXUNY41JAR530+Naz3MgX2XD1bq0BCBcbFGt0ybgo80YM mLvvP8YpnAyMfMPMCGdOLBY= X-Google-Smtp-Source: ABdhPJwoTFH0E0p8PB2diBbPX7wR8FqwAcpVy617XVpKhy36D3+11mywcV76iigm3DFRF4Y5w2zP0Q== X-Received: by 2002:a17:90a:e28d:: with SMTP id d13mr19546896pjz.128.1590397919968; Mon, 25 May 2020 02:11:59 -0700 (PDT) Received: from localhost ([2409:10:2e40:5100:6e29:95ff:fe2d:8f34]) by smtp.gmail.com with ESMTPSA id q15sm12455429pfh.188.2020.05.25.02.11.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 25 May 2020 02:11:59 -0700 (PDT) From: Sergey Senozhatsky X-Google-Original-From: Sergey Senozhatsky Date: Mon, 25 May 2020 18:11:57 +0900 To: Petr Mladek Cc: Tetsuo Handa , Andrew Morton , linux-kernel@vger.kernel.org, Dmitry Vyukov , Ondrej Mosnacek , Sergey Senozhatsky , Steven Rostedt Subject: Re: [PATCH] twist: allow converting pr_devel()/pr_debug() into printk(KERN_DEBUG) Message-ID: <20200525091157.GF755@jagdpanzerIV.localdomain> References: <20200524145034.10697-1-penguin-kernel@I-love.SAKURA.ne.jp> <20200525084218.GC5300@linux-b0ei> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200525084218.GC5300@linux-b0ei> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (20/05/25 10:42), Petr Mladek wrote: > On Sun 2020-05-24 23:50:34, Tetsuo Handa wrote: > > syzbot found a NULL pointer dereference bug inside mptcp_recvmsg() due to > > ssock == NULL, but this bug manifested inside selinux_socket_recvmsg() > > because pr_debug() was no-op [1]. > > > > pr_debug("fallback-read subflow=%p", > > mptcp_subflow_ctx(ssock->sk)); > > copied = sock_recvmsg(ssock, msg, flags); > > The NULL pointer deference was found even without this patch. > This patch would just cause that it will manifest itself on another > place. What is the benefit, please? Right, I don't get this patch. A NULL-deref is still a NULL pointer deref. pr_debug() will fault reading one byte from the address and print something like "fallback-read subflow=(efault)" to printk-safe buffer, but then sock_recvmsg() is still going to do its thing. -ss