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=-2.6 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, USER_AGENT_MUTT autolearn=ham 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 66BAEC04AAF for ; Tue, 21 May 2019 07:39:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3846B21019 for ; Tue, 21 May 2019 07:39:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="O5AMhsix" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727130AbfEUHjN (ORCPT ); Tue, 21 May 2019 03:39:13 -0400 Received: from mail-pg1-f196.google.com ([209.85.215.196]:33244 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726059AbfEUHjN (ORCPT ); Tue, 21 May 2019 03:39:13 -0400 Received: by mail-pg1-f196.google.com with SMTP id h17so8157600pgv.0 for ; Tue, 21 May 2019 00:39:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=ertU93vLyvZbyhqI5mMBCSgKS6RS62cHiIXJIbfZNjU=; b=O5AMhsixq0BooHonQfVIB2VNXmTe/upfgN0xFMResCgzVpKx7PZuo61IDBt/QfI8Mx h/TTholMO0hFP/jLW2R0GvL5yHsCbPwdDDJyDRsMzUZyIU319q12ERfoxn5kdrRNrm8R Wc5k+PxcNkwpEyVz7LdLXGMPTzZFVe2JHM8nMXgbduYLjfc2lW8ttCewuzVKGl6ZRUcr u2X2AioGajC9HHYWrL3YsQT6NwZFoJ8D2sio2OrLAztRJJbshsjZMm2fDyIh/V+dGGab AKf4SwIl0f5kVzz/Qpd9V+gtHdkW2SevAMnbNC/6tZpvveJ7HqCUJLmlMB36hYOV+ngv LvTA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=ertU93vLyvZbyhqI5mMBCSgKS6RS62cHiIXJIbfZNjU=; b=gZkQ0xzz0EbTHCX4u9DtghHu1JepasHG+o1RYFcA9PAqoD8aHHkv2yNWWud8g/R+Pn yMlslPsuxZ1O1kGQm537FI4vNHH6t81FWOtz2CTAAdngogAHQ9efMPYv6LOXa9Iza5nE keH1sW6WdicxeOv28bJaQnxmvIhUcx0IEGfmsiKKyp5gXzCAVH628L6sATM5kYKKLAVZ WI7zkj0rZXXn9N/3zenEgXvjkX4PH7PuoSV3UTdYTAd5Q6QQQxsEuA62b1I5185ak7Qx AamVVT+KZKQ8x1D4V4XFjAGu/OGQp/LC1+ojbXxsQ5AIMbsDYm7q3nD36J3GZ4GIUZVC U+Iw== X-Gm-Message-State: APjAAAXpIgER1nQa9+gbE7bU05SVZW3r/2raTAmAm6xaeyXXf3Oooky6 2AiV7/xCRtUkHmZQwgEUQm/LfCTycs0= X-Google-Smtp-Source: APXvYqyFMJXJBetRH/tQItKUh0um5jcuAmaHg3cXa+hKpXi0zE3v54WVcDDI6HQmI2Z3O51KkVljdw== X-Received: by 2002:a63:2c14:: with SMTP id s20mr62763921pgs.182.1558424352594; Tue, 21 May 2019 00:39:12 -0700 (PDT) Received: from zhanggen-UX430UQ ([66.42.35.75]) by smtp.gmail.com with ESMTPSA id s66sm23940174pfb.37.2019.05.21.00.39.09 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 21 May 2019 00:39:12 -0700 (PDT) Date: Tue, 21 May 2019 15:39:01 +0800 From: Gen Zhang To: Nicolas Pitre Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] vt: Fix a missing-check bug in drivers/tty/vt/vt.c Message-ID: <20190521073901.GF5263@zhanggen-UX430UQ> References: <20190521022940.GA4858@zhanggen-UX430UQ> <20190521030905.GB5263@zhanggen-UX430UQ> <20190521040019.GD5263@zhanggen-UX430UQ> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 21, 2019 at 12:30:38AM -0400, Nicolas Pitre wrote: > Now imagine that MIN_NR_CONSOLES is defined to 10 instead of 1. > > What happens with allocated memory if the err_vc condition is met on the > 5th loop? Yes, vc->vc_screenbuf from the last loop is still not freed, right? I don't have idea to solve this one. Could please give some advice? Since we have to consider the err_vc condition. > If err_vc_screenbuf condition is encountered on the 5th loop (curcons = > 4), what is the value of vc_cons[4].d? Isn't it the same as vc that you > just freed? > > > Nicolas Thanks for your explaination! You mean a double free situation may happen, right? But in vc_allocate() there is also such a kfree(vc) and vc_cons[currcons].d = NULL operation. This situation is really confusing me. Thanks Gen