linux-kernel - [PATCH 2/2] Ensure num_actions is not a negative

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Message-ID: <20230901010437.126631-3-joao@overdrivepizza.com>
Date:   Thu, 31 Aug 2023 18:04:37 -0700
From:   joao@...rdrivepizza.com
To:     pablo@...filter.org, netfilter-devel@...r.kernel.org,
        coreteam@...filter.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, joao@...rdrivepizza.com
Cc:     kadlec@...filter.org, fw@...len.de, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        rkannoth@...vell.com, wojciech.drewek@...el.com,
        steen.hegenlund@...rohip.com, keescook@...omium.org,
        Joao Moreira <joao.moreira@...el.com>
Subject: [PATCH 2/2] Ensure num_actions is not a negative

From: Joao Moreira <joao.moreira@...el.com>

In nft_flow_rule_create function, num_actions is a signed integer. Yet,
it is processed within a loop which increments its value. To prevent an
overflow from occurring, check if num_actions is not only equal to 0,
but also not negative.

After checking with maintainers, it was mentioned that front-end will
cap the num_actions vlaue and that it is not possible to reach such
condition for an overflow. Yet, for correctness, it is still better to
fix this.

Signed-off-by: Joao Moreira <joao.moreira@...el.com>
---
 net/netfilter/nf_tables_offload.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/nf_tables_offload.c b/net/netfilter/nf_tables_offload.c
index 12ab78fa5d84..20dbc95de895 100644
--- a/net/netfilter/nf_tables_offload.c
+++ b/net/netfilter/nf_tables_offload.c
@@ -102,7 +102,7 @@ struct nft_flow_rule *nft_flow_rule_create(struct net *net,
 		expr = nft_expr_next(expr);
 	}
 
-	if (num_actions == 0)
+	if (num_actions <= 0)
 		return ERR_PTR(-EOPNOTSUPP);
 
 	flow = nft_flow_rule_alloc(num_actions);
-- 
2.41.0