netfilter: nf_tables: prevent shift wrap in nft_chain_parse_hook()

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 <dan.carpenter@oracle.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index ef7772e976cc802afc64ea25d28f1fbecde773be..1606eaa5ae0da368f4a692264456e18dfe27ec8d 100644 (file)
--- 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 &&