[PATCH AUTOSEL 4.19 46/81] netfilter: nf_tables: prevent shift wrap in nft_chain_parse_hook()

Sasha Levin
2019-05-07T05:58:05Z

From: Dan Carpenter <dan.carpenter@oracle.com>

[ Upstream commit 33d1c018179d0a30c39cc5f1682b77867282694b ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 1af54119bafc..f272f9538c44 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -1496,7 +1496,7 @@ 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 &&
--
2.20.1