From patchwork Mon Oct 13 15:43:43 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chen Gang X-Patchwork-Id: 399228 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 552B4140081 for ; Tue, 14 Oct 2014 02:46:54 +1100 (EST) Received: from localhost ([::1]:34100 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Xdhpj-0002Jj-2U for incoming@patchwork.ozlabs.org; Mon, 13 Oct 2014 11:46:51 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37995) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XdhpJ-00021H-V1 for qemu-devel@nongnu.org; Mon, 13 Oct 2014 11:46:34 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XdhpA-0000F0-Pn for qemu-devel@nongnu.org; Mon, 13 Oct 2014 11:46:25 -0400 Received: from mail-pd0-x233.google.com ([2607:f8b0:400e:c02::233]:35146) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Xdhos-0000Cw-9U; Mon, 13 Oct 2014 11:45:58 -0400 Received: by mail-pd0-f179.google.com with SMTP id r10so5800004pdi.38 for ; Mon, 13 Oct 2014 08:45:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:content-type:content-transfer-encoding; bh=aZ3wKs86fDes2Z2/KOxSAUgCZoksFGR4YRb1sEsn3Ko=; b=BD03lZXnc1+FtB8MAOTfRfBGVj3H0tB9FGZljhcZCSw2sJwgPxKd9eXu3DVNpKCmIf l9SJea/LcJgSPml5/klwhZakOEIu9F6PNMQhVkbmP9mhjANsCnxtVo2u/2jlK5532RNZ OSIY5r7tUYAxkIgjLPF9katM/wO8A0qdoI2noBO+8/0VX4SoIYJuUz/Fx7wyfSxKEP9O jVkSW6Vh7KHxeEtVvD0Sltg1CXs+6gcjosjpciK9Dhg5/TXU3t+JYmw2stBVwxEVLwDC esWrYXSLgm2gZCAh4u2hoBl2FOafgIHve70eEt+c5NAjvaMBiOkeeEfJdkMiGGO2uf2t 6HDQ== X-Received: by 10.68.57.226 with SMTP id l2mr2582510pbq.147.1413214671986; Mon, 13 Oct 2014 08:37:51 -0700 (PDT) Received: from ShengShiZhuChengdeMacBook-Pro.local ([223.72.65.118]) by mx.google.com with ESMTPSA id np11sm11534068pdb.78.2014.10.13.08.37.48 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 13 Oct 2014 08:37:50 -0700 (PDT) Message-ID: <543BF32F.4020205@gmail.com> Date: Mon, 13 Oct 2014 23:43:43 +0800 From: Chen Gang User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:31.0) Gecko/20100101 Thunderbird/31.1.2 MIME-Version: 1.0 To: Alexander Graf , pbonzini@redhat.com References: <543BE352.3080609@gmail.com> <543BE616.1000707@suse.de> In-Reply-To: <543BE616.1000707@suse.de> X-detected-operating-system: by eggs.gnu.org: Error: Malformed IPv6 address (bad octet value). X-Received-From: 2607:f8b0:400e:c02::233 Cc: qemu-trivial@nongnu.org, qemu-ppc@nongnu.org, qemu-devel , kvm@vger.kernel.org Subject: Re: [Qemu-devel] [PATCH] target-ppc: kvm: Fix memory overflow issue about strncat() X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org On 10/13/14 22:47, Alexander Graf wrote: > > Could you please instead rewrite it to use g_strdup_printf() rather than > strncat()s? That way we resolve all string pitfalls automatically - and > this code is not the fast path, so doing an extra memory allocation is ok. > I guess, it is a personal taste. For me, it may need additional variable for g_strdup_printf(), and not save code lines, but *sprintf() is more readable than str*cat(). The related code may like below (welcome any improvement for it): For me, it is really a personal taste, so if the maintainer feels the diff above is OK, I shall send patch v2 for it within 2 days. Thanks. diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c index 66e7ce5..cea6a87 100644 --- a/target-ppc/kvm.c +++ b/target-ppc/kvm.c @@ -1782,7 +1782,7 @@ static int kvmppc_find_cpu_dt(char *buf, int buf_len) * format) */ static uint64_t kvmppc_read_int_cpu_dt(const char *propname) { - char buf[PATH_MAX]; + char buf[PATH_MAX], *tmp; union { uint32_t v32; uint64_t v64; @@ -1794,10 +1794,10 @@ static uint64_t kvmppc_read_int_cpu_dt(const char *propname) return -1; } - strncat(buf, "/", sizeof(buf) - strlen(buf) - 1); - strncat(buf, propname, sizeof(buf) - strlen(buf) - 1); + tmp = g_strdup_printf("%s/%s", buf, propname); - f = fopen(buf, "rb"); + f = fopen(tmp, "rb"); + g_free(buf); if (!f) { return -1; }