From patchwork Tue Mar 13 01:13:49 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Gustavo A. R. Silva" X-Patchwork-Id: 10277699 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 0834E603B5 for ; Tue, 13 Mar 2018 01:14:09 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E957C28ED3 for ; Tue, 13 Mar 2018 01:14:08 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id DDC23289BB; Tue, 13 Mar 2018 01:14:08 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 1F771289BB for ; Tue, 13 Mar 2018 01:14:07 +0000 (UTC) Received: (qmail 18431 invoked by uid 550); 13 Mar 2018 01:14:06 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 18391 invoked from network); 13 Mar 2018 01:14:04 -0000 Date: Mon, 12 Mar 2018 20:13:49 -0500 From: "Gustavo A. R. Silva" To: Pablo Neira Ayuso , Jozsef Kadlecsik , Florian Westphal , "David S. Miller" Cc: netfilter-devel@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Kernel Hardening , Kees Cook , "Gustavo A. R. Silva" Subject: [PATCH] netfilter: nf_tables: remove VLA usage Message-ID: <20180313011349.GA31826@embeddedgus> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.5.24 (2015-08-30) X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator4166.hostgator.com X-AntiAbuse: Original Domain - lists.openwall.com X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - embeddedor.com X-BWhitelist: no X-Source-IP: 189.175.117.58 X-Source-L: No X-Exim-ID: 1evYVj-001Iif-SF X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedgus) [189.175.117.58]:47598 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 9 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes X-Virus-Scanned: ClamAV using ClamSMTP In preparation to enabling -Wvla, remove VLA and replace it with dynamic memory allocation. From a security viewpoint, the use of Variable Length Arrays can be a vector for stack overflow attacks. Also, in general, as the code evolves it is easy to lose track of how big a VLA can get. Thus, we can end up having segfaults that are hard to debug. Also, fixed as part of the directive to remove all VLAs from the kernel: https://lkml.org/lkml/2018/3/7/621 Signed-off-by: Gustavo A. R. Silva --- net/netfilter/nf_tables_api.c | 23 +++++++++++++++-------- 1 file changed, 15 insertions(+), 8 deletions(-) diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c index 3f815b6..ea76903 100644 --- a/net/netfilter/nf_tables_api.c +++ b/net/netfilter/nf_tables_api.c @@ -4357,16 +4357,20 @@ static struct nft_object *nft_obj_init(const struct nft_ctx *ctx, const struct nft_object_type *type, const struct nlattr *attr) { - struct nlattr *tb[type->maxattr + 1]; + struct nlattr **tb; const struct nft_object_ops *ops; struct nft_object *obj; - int err; + int err = -ENOMEM; + + tb = kcalloc(type->maxattr + 1, sizeof(*tb), GFP_KERNEL); + if (!tb) + goto err1; if (attr) { err = nla_parse_nested(tb, type->maxattr, attr, type->policy, NULL); if (err < 0) - goto err1; + goto err2; } else { memset(tb, 0, sizeof(tb[0]) * (type->maxattr + 1)); } @@ -4375,7 +4379,7 @@ static struct nft_object *nft_obj_init(const struct nft_ctx *ctx, ops = type->select_ops(ctx, (const struct nlattr * const *)tb); if (IS_ERR(ops)) { err = PTR_ERR(ops); - goto err1; + goto err2; } } else { ops = type->ops; @@ -4383,18 +4387,21 @@ static struct nft_object *nft_obj_init(const struct nft_ctx *ctx, err = -ENOMEM; obj = kzalloc(sizeof(*obj) + ops->size, GFP_KERNEL); - if (obj == NULL) - goto err1; + if (!obj) + goto err2; err = ops->init(ctx, (const struct nlattr * const *)tb, obj); if (err < 0) - goto err2; + goto err3; obj->ops = ops; + kfree(tb); return obj; -err2: +err3: kfree(obj); +err2: + kfree(tb); err1: return ERR_PTR(err); }