From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Carpenter Date: Sat, 06 Apr 2019 05:26:52 +0000 Subject: [PATCH v2] netfilter: nf_tables: prevent shift wrap in nft_chain_parse_hook() Message-Id: <20190406052652.GA20963@kadam> List-Id: In-Reply-To: <20190402133038.GA18575@kadam> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Pablo Neira Ayuso Cc: Jozsef Kadlecsik , Florian Westphal , netfilter-devel@vger.kernel.org, coreteam@netfilter.org, kernel-janitors@vger.kernel.org I believe that "hook->num" can be up to UINT_MAX. Shifting more than 31 bits would is undefined in C but in practice it would lead to shift wrapping. That would lead to an array overflow in nf_tables_addchain(): ops->hook = hook.type->hooks[ops->hooknum]; Fixes: fe19c04ca137 ("netfilter: nf_tables: remove nhooks field from struct nft_af_info") Signed-off-by: Dan Carpenter --- v2: In my original fix I thought making shifts unsigned was defined in C but it's not. My original patch didn't fix or change runtime at all. Thanks to Florian Westphal for his help on this. net/netfilter/nf_tables_api.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c index ef7772e976cc..1606eaa5ae0d 100644 --- a/net/netfilter/nf_tables_api.c +++ b/net/netfilter/nf_tables_api.c @@ -1545,7 +1545,7 @@ static int nft_chain_parse_hook(struct net *net, if (IS_ERR(type)) return PTR_ERR(type); } - if (!(type->hook_mask & (1 << hook->num))) + if (hook->num > NF_MAX_HOOKS || !(type->hook_mask & (1 << hook->num))) return -EOPNOTSUPP; if (type->type = NFT_CHAIN_T_NAT && -- 2.17.1