[PATCH] netfilter: nf_tables: prevent shift wrap in nft_chain_parse_hook()

Dan Carpenter
2019-04-02T13:30:38Z

I believe that "hook->num" can be up to UINT_MAX so the shift has to
be unsigned or shifting more than 31 is undefined. It's possible that
this leads to 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>
---
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..b6e48fe7c776 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 (!(type->hook_mask & (1U << hook->num)))
return -EOPNOTSUPP;

if (type->type = NFT_CHAIN_T_NAT &&
--
2.17.1