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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 46E3BC433FE for ; Fri, 22 Apr 2022 02:45:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1443498AbiDVCsP (ORCPT ); Thu, 21 Apr 2022 22:48:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42644 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235671AbiDVCsO (ORCPT ); Thu, 21 Apr 2022 22:48:14 -0400 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 674642ED41; Thu, 21 Apr 2022 19:45:21 -0700 (PDT) Received: from kwepemi500012.china.huawei.com (unknown [172.30.72.55]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4KkzDM5wpvzCrdw; Fri, 22 Apr 2022 10:40:51 +0800 (CST) Received: from [10.67.110.176] (10.67.110.176) by kwepemi500012.china.huawei.com (7.221.188.12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Fri, 22 Apr 2022 10:45:18 +0800 Subject: Re: [PATCH -next] libbpf: Add additional null-pointer checking in make_parent_dir To: Andrii Nakryiko CC: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin Lau , Song Liu , Yonghong Song , john fastabend , KP Singh , Networking , bpf , open list , , References: <20220421130056.2510372-1-cuigaosheng1@huawei.com> From: cuigaosheng Message-ID: <45fdf83c-7492-1c31-af8d-7b2c9bdaf5a7@huawei.com> Date: Fri, 22 Apr 2022 10:45:08 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.67.110.176] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To kwepemi500012.china.huawei.com (7.221.188.12) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I don't understand why we don't check path for NULL, bpf_link__pin is an external interface, It will be called by external functions and provide input parameters, for example in samples/bpf/hbm.c: > 201 link = bpf_program__attach_cgroup(bpf_prog, cg1); 202 if > (libbpf_get_error(link)) { 203 fprintf(stderr, "ERROR: > bpf_program__attach_cgroup failed\n"); 204 goto err; 205 } 206 207 > sprintf(cg_pin_path, "/sys/fs/bpf/hbm%d", cg_id); 208 rc = > bpf_link__pin(link, cg_pin_path); 209 if (rc < 0) { 210 printf("ERROR: > bpf_link__pin failed: %d\n", rc); 211 goto err; 212 } if cg_pin_path is NULL, strdup(NULL) will trigger a segmentation fault in make_parent_dir, I think we should avoid this and add null-pointer checking for path, just like check_path: > 7673 static int check_path(const char *path) 7674 { 7675 char *cp, > errmsg[STRERR_BUFSIZE]; 7676 struct statfs st_fs; 7677 char *dname, > *dir; 7678 int err = 0; 7679 7680 if (path == NULL) 7681 return > -EINVAL; 7682 7683 dname = strdup(path); 7684 if (dname == NULL) 7685 > return -ENOMEM; 7686 7687 dir = dirname(dname); 7688 if (statfs(dir, > &st_fs)) { 7689 cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg)); > 7690 pr_warn("failed to statfs %s: %s\n", dir, cp); 7691 err = -errno; > 7692 } 7693 free(dname); 7694 7695 if (!err && st_fs.f_type != > BPF_FS_MAGIC) { 7696 pr_warn("specified path %s is not on BPF FS\n", > path); 7697 err = -EINVAL; 7698 } 7699 7700 return err; 7701 } Thanks. 在 2022/4/22 0:55, Andrii Nakryiko 写道: > On Thu, Apr 21, 2022 at 6:01 AM Gaosheng Cui wrote: >> The make_parent_dir is called without null-pointer checking for path, >> such as bpf_link__pin. To ensure there is no null-pointer dereference >> in make_parent_dir, so make_parent_dir requires additional null-pointer >> checking for path. >> >> Signed-off-by: Gaosheng Cui >> --- >> tools/lib/bpf/libbpf.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c >> index b53e51884f9e..5786e6184bf5 100644 >> --- a/tools/lib/bpf/libbpf.c >> +++ b/tools/lib/bpf/libbpf.c >> @@ -7634,6 +7634,9 @@ static int make_parent_dir(const char *path) >> char *dname, *dir; >> int err = 0; >> >> + if (path == NULL) >> + return -EINVAL; >> + > API contract is that path shouldn't be NULL. Just like we don't check > link, obj, prog for NULL in every single API, I don't think we need to > do it here, unless I'm missing something? > >> dname = strdup(path); >> if (dname == NULL) >> return -ENOMEM; >> -- >> 2.25.1 >> > .