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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 3D0A5C43381 for ; Wed, 13 Mar 2019 10:31:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1175E2184C for ; Wed, 13 Mar 2019 10:31:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726568AbfCMKbU (ORCPT ); Wed, 13 Mar 2019 06:31:20 -0400 Received: from ivanoab6.miniserver.com ([5.153.251.140]:41844 "EHLO www.kot-begemot.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725864AbfCMKbU (ORCPT ); Wed, 13 Mar 2019 06:31:20 -0400 X-Greylist: delayed 2743 seconds by postgrey-1.27 at vger.kernel.org; Wed, 13 Mar 2019 06:31:19 EDT Received: from jain.kot-begemot.co.uk ([192.168.3.3] helo=smaug.kot-begemot.co.uk) by www.kot-begemot.co.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1h40S3-0007Fk-MU; Wed, 13 Mar 2019 09:45:31 +0000 Received: from jain.kot-begemot.co.uk ([192.168.3.3]) by smaug.kot-begemot.co.uk with esmtp (Exim 4.89) (envelope-from ) id 1h40S2-0005gh-JM; Wed, 13 Mar 2019 09:45:30 +0000 Subject: Re: [PATCH] um: remove uses of variable length arrays To: Bartosz Golaszewski , Jeff Dike , Richard Weinberger Cc: Bartosz Golaszewski , linux-um@lists.infradead.org, linux-kernel@vger.kernel.org References: <20190312133047.16201-1-brgl@bgdev.pl> From: Anton Ivanov Message-ID: <56704758-ee74-0e9b-de1c-1dc94deda8d7@cambridgegreys.com> Date: Wed, 13 Mar 2019 09:45:30 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <20190312133047.16201-1-brgl@bgdev.pl> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Clacks-Overhead: GNU Terry Pratchett Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/03/2019 13:30, Bartosz Golaszewski wrote: > From: Bartosz Golaszewski > > While the affected code is run in user-mode, the build still warns > about it. Convert all uses of VLA to dynamic allocations. > > Signed-off-by: Bartosz Golaszewski > --- > arch/um/os-Linux/umid.c | 36 +++++++++++++++++++++++++++--------- > 1 file changed, 27 insertions(+), 9 deletions(-) > > diff --git a/arch/um/os-Linux/umid.c b/arch/um/os-Linux/umid.c > index 998fbb445458..e261656fe9d7 100644 > --- a/arch/um/os-Linux/umid.c > +++ b/arch/um/os-Linux/umid.c > @@ -135,12 +135,18 @@ static int remove_files_and_dir(char *dir) > */ > static inline int is_umdir_used(char *dir) > { > - char file[strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")]; > - char pid[sizeof("nnnnn\0")], *end; > + char pid[sizeof("nnnnn\0")], *end, *file; > int dead, fd, p, n, err; > + size_t filelen; > > - n = snprintf(file, sizeof(file), "%s/pid", dir); > - if (n >= sizeof(file)) { > + err = asprintf(&file, "%s/pid", dir); > + if (err < 0) > + return 0; > + > + filelen = strlen(file); > + > + n = snprintf(file, filelen, "%s/pid", dir); > + if (n >= filelen) { > printk(UM_KERN_ERR "is_umdir_used - pid filename too long\n"); > err = -E2BIG; > goto out; > @@ -185,6 +191,7 @@ static inline int is_umdir_used(char *dir) > out_close: > close(fd); > out: > + free(file); > return 0; > } > > @@ -210,18 +217,21 @@ static int umdir_take_if_dead(char *dir) > > static void __init create_pid_file(void) > { > - char file[strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")]; > - char pid[sizeof("nnnnn\0")]; > + char pid[sizeof("nnnnn\0")], *file; > int fd, n; > > - if (umid_file_name("pid", file, sizeof(file))) > + file = malloc(strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")); > + if (!file) > return; > > + if (umid_file_name("pid", file, sizeof(file))) > + goto out; > + > fd = open(file, O_RDWR | O_CREAT | O_EXCL, 0644); > if (fd < 0) { > printk(UM_KERN_ERR "Open of machine pid file \"%s\" failed: " > "%s\n", file, strerror(errno)); > - return; > + goto out; > } > > snprintf(pid, sizeof(pid), "%d\n", getpid()); > @@ -231,6 +241,8 @@ static void __init create_pid_file(void) > errno); > > close(fd); > +out: > + free(file); > } > > int __init set_umid(char *name) > @@ -385,13 +397,19 @@ __uml_setup("uml_dir=", set_uml_dir, > > static void remove_umid_dir(void) > { > - char dir[strlen(uml_dir) + UMID_LEN + 1], err; > + char *dir, err; > + > + dir = malloc(strlen(uml_dir) + UMID_LEN + 1); > + if (!dir) > + return; > > sprintf(dir, "%s%s", uml_dir, umid); > err = remove_files_and_dir(dir); > if (err) > os_warn("%s - remove_files_and_dir failed with err = %d\n", > __func__, err); > + > + free(dir); > } > > __uml_exitcall(remove_umid_dir); > Thanks for bringing it up. It helped me notice that this is actually broken. PID can be more than 5 digits nowdays. -- Anton R. Ivanov Cambridgegreys Limited. Registered in England. Company Number 10273661 https://www.cambridgegreys.com/