From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kees Cook Subject: [PATCH] netfilter: nfnetlink: Remove VLA usage Date: Tue, 29 May 2018 17:35:25 -0700 Message-ID: <20180530003525.GA18642@beast> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jozsef Kadlecsik , Florian Westphal , "David S. Miller" , netfilter-devel@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Pablo Neira Ayuso Return-path: Received: from mail-pf0-f194.google.com ([209.85.192.194]:45040 "EHLO mail-pf0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935643AbeE3Af2 (ORCPT ); Tue, 29 May 2018 20:35:28 -0400 Received: by mail-pf0-f194.google.com with SMTP id q22-v6so8085010pff.11 for ; Tue, 29 May 2018 17:35:28 -0700 (PDT) Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: In the quest to remove all stack VLA usage from the kernel[1], this allocates the maximum size expected for all possible attrs and adds a sanity-check to make sure nothing gets out of sync. [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com Signed-off-by: Kees Cook --- net/netfilter/nfnetlink.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c index 03ead8a9e90c..0cb395f9627e 100644 --- a/net/netfilter/nfnetlink.c +++ b/net/netfilter/nfnetlink.c @@ -28,6 +28,7 @@ #include #include +#include MODULE_LICENSE("GPL"); MODULE_AUTHOR("Harald Welte "); @@ -37,6 +38,11 @@ MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER); rcu_dereference_protected(table[(id)].subsys, \ lockdep_nfnl_is_held((id))) +#define NFTA_MAX_ATTR max(max(max(NFTA_CHAIN_MAX, NFTA_FLOWTABLE_MAX),\ + max(NFTA_OBJ_MAX, NFTA_RULE_MAX)), \ + max(NFTA_TABLE_MAX, \ + max(NFTA_SET_ELEM_LIST_MAX, NFTA_SET_MAX))) + static struct { struct mutex mutex; const struct nfnetlink_subsystem __rcu *subsys; @@ -185,11 +191,17 @@ static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, { int min_len = nlmsg_total_size(sizeof(struct nfgenmsg)); u8 cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type); - struct nlattr *cda[ss->cb[cb_id].attr_count + 1]; + struct nlattr *cda[NFTA_MAX_ATTR + 1]; struct nlattr *attr = (void *)nlh + min_len; int attrlen = nlh->nlmsg_len - min_len; __u8 subsys_id = NFNL_SUBSYS_ID(type); + /* Sanity-check NFTA_MAX_ATTR */ + if (ss->cb[cb_id].attr_count > NFTA_MAX_ATTR) { + rcu_read_unlock(); + return -ENOMEM; + } + err = nla_parse(cda, ss->cb[cb_id].attr_count, attr, attrlen, ss->cb[cb_id].policy, extack); if (err < 0) { @@ -379,10 +391,16 @@ static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh, { int min_len = nlmsg_total_size(sizeof(struct nfgenmsg)); u8 cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type); - struct nlattr *cda[ss->cb[cb_id].attr_count + 1]; + struct nlattr *cda[NFTA_MAX_ATTR + 1]; struct nlattr *attr = (void *)nlh + min_len; int attrlen = nlh->nlmsg_len - min_len; + /* Sanity-check NFTA_MAX_ATTR */ + if (ss->cb[cb_id].attr_count > NFTA_MAX_ATTR) { + err = -ENOMEM; + goto ack; + } + err = nla_parse(cda, ss->cb[cb_id].attr_count, attr, attrlen, ss->cb[cb_id].policy, NULL); if (err < 0) -- 2.17.0 -- Kees Cook Pixel Security