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=-8.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 99D1FC468C1 for ; Mon, 10 Jun 2019 06:45:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 68AE82085A for ; Mon, 10 Jun 2019 06:45:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="YiHkTJdx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387858AbfFJGp2 (ORCPT ); Mon, 10 Jun 2019 02:45:28 -0400 Received: from mail-pf1-f194.google.com ([209.85.210.194]:44364 "EHLO mail-pf1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387797AbfFJGp2 (ORCPT ); Mon, 10 Jun 2019 02:45:28 -0400 Received: by mail-pf1-f194.google.com with SMTP id t16so4681788pfe.11 for ; Sun, 09 Jun 2019 23:45:28 -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=AXxwZFqkJLSKlo1AKtUaQ/ENUlkKBcpyhgleO3ow388=; b=YiHkTJdx7yCQJW8EhCRhbAexTIwEPNmnltUScnOW70LR5R4M0zGWwRb1Azugg0mJKW 1NA30+nTtQdDYboc8TiR9TieUCKkKkTaYdMz7DS6OCELNzNdmg2HxnOUWymdQ3zfq85E bfsgwfd/uS3RMxh83/W534VSOilBSyr0kmQ0X9Iq95QtCCWd1/4cB4VqWzK5Xwrj9Tc5 zmmhH9ZhZi2uBbk1EEE8Y5CCPprTI/kSMcOTWuTBghacpXttDiXPnnXt45grFnDt7MXu VaDUVAbJ8ZgFLxsF4plIJ28cBfq2CMUFkbn8+Ho0M8O08U86avUP+fao+YizCgc2QqS5 DdHw== 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=AXxwZFqkJLSKlo1AKtUaQ/ENUlkKBcpyhgleO3ow388=; b=tMgM2Tu3yVpHn+nt/1vw5W4FINxrAVgQ/d3Gl//GZwZSDt6yXK0pAup2XoCfg+38Cr /UO37Zf2FOSUfNo18quhGs8YZ49tX6q8fUomGwhQAz/d0FwKp6BLYcQEhbWY0+EkybYw I+MHJa2BymwCM8leD42T00xFjxE4m2HEXm05PfbKWixEJTU1u5YFVOLkEDDxjxpiIkjH 7UBiOdvM5J3qCcd+6XwhLFYucM/vY/sIu4c4rP6g+jbDjP6MuZkA+7U46QToI7s5FPME 0V/jkCeT4/W8w3m876JA2/HF84wX1idmVIar+xqasFhzf8vneLe3ziO+Ljb46OFYEqKr 79Zg== X-Gm-Message-State: APjAAAV8z9cayVell3Qa7CUc+b915k7VdgofknYs1uplpb3W/sWgpsvB sl0CEEz164OIZVOhKbfp3JouOQHg4MsmnQ== X-Google-Smtp-Source: APXvYqw08rKgZJAkQBntaYmCPFTNxHfKWkcs3bOrEThz724Nqp1BmapHkmdPOiD5NJuFIDU1d/qeZg== X-Received: by 2002:a63:5207:: with SMTP id g7mr13953365pgb.356.1560149127632; Sun, 09 Jun 2019 23:45:27 -0700 (PDT) Received: from ubuntu ([104.192.108.9]) by smtp.gmail.com with ESMTPSA id s17sm8726251pfm.74.2019.06.09.23.45.24 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 09 Jun 2019 23:45:27 -0700 (PDT) Date: Sun, 9 Jun 2019 23:45:21 -0700 From: Gen Zhang To: Nicolas Pitre Cc: Greg KH , jslaby@suse.com, kilobyte@angband.pl, textshell@uchuujin.de, mpatocka@redhat.com, daniel.vetter@ffwll.ch, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] vt: Fix a missing-check bug in con_init() Message-ID: <20190610064519.GA3143@ubuntu> References: <20190528004529.GA12388@zhanggen-UX430UQ> <20190608160138.GA3840@zhanggen-UX430UQ> <20190608162219.GB11699@kroah.com> 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 Sat, Jun 08, 2019 at 08:15:46PM -0400, Nicolas Pitre wrote: > On Sat, 8 Jun 2019, Greg KH wrote: > > > On Sun, Jun 09, 2019 at 12:01:38AM +0800, Gen Zhang wrote: > > > On Tue, May 28, 2019 at 08:45:29AM +0800, Gen Zhang wrote: > > > > In function con_init(), the pointer variable vc_cons[currcons].d, vc and > > > > vc->vc_screenbuf is allocated by kzalloc(). And they are used in the > > > > following codes. However, kzalloc() returns NULL when fails, and null > > > > pointer dereference may happen. And it will cause the kernel to crash. > > > > Therefore, we should check the return value and handle the error. > > > > > > > > Further, since the allcoation is in a loop, we should free all the > > > > allocated memory in a loop. > > > > > > > > Signed-off-by: Gen Zhang > > > > Reviewed-by: Nicolas Pitre > > > > --- > > > > diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c > > > > index fdd12f8..d50f68f 100644 > > > > --- a/drivers/tty/vt/vt.c > > > > +++ b/drivers/tty/vt/vt.c > > > > @@ -3350,10 +3350,14 @@ static int __init con_init(void) > > > > > > > > for (currcons = 0; currcons < MIN_NR_CONSOLES; currcons++) { > > > > vc_cons[currcons].d = vc = kzalloc(sizeof(struct vc_data), GFP_NOWAIT); > > > > + if (!vc) > > > > + goto fail1; > > > > INIT_WORK(&vc_cons[currcons].SAK_work, vc_SAK); > > > > tty_port_init(&vc->port); > > > > visual_init(vc, currcons, 1); > > > > vc->vc_screenbuf = kzalloc(vc->vc_screenbuf_size, GFP_NOWAIT); > > > > + if (!vc->vc_screenbuf) > > > > + goto fail2; > > > > vc_init(vc, vc->vc_rows, vc->vc_cols, > > > > currcons || !vc->vc_sw->con_save_screen); > > > > } > > > > @@ -3375,6 +3379,16 @@ static int __init con_init(void) > > > > register_console(&vt_console_driver); > > > > #endif > > > > return 0; > > > > +fail1: > > > > + while (currcons > 0) { > > > > + currcons--; > > > > + kfree(vc_cons[currcons].d->vc_screenbuf); > > > > +fail2: > > > > + kfree(vc_cons[currcons].d); > > > > + vc_cons[currcons].d = NULL; > > > > + } > > > > Wait, will that even work? You can jump into the middle of a while > > loop? > > Absolutely. > > > Ugh, that's beyond ugly. > > That was me who suggested to do it like that. To me, this is nicer than > the proposed alternatives. For an error path that is rather unlikely to > happen, I think this is a very concise and eleguant way to do it. > > > And please provide "real" names for the > > labels, "fail1" and "fail2" do not tell anything here. > > That I agree with. > > > Nicolas Thanks for your comments. Then am I supposed to revise the patch and send a v4 version? Thanks Gen