netdev - [PATCH 1/4] netfilter: nf_flow_table: fix big-endian integer overflow

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Message-Id: <20191226163956.672174-2-pablo@netfilter.org>
Date:   Thu, 26 Dec 2019 17:39:53 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     netfilter-devel@...r.kernel.org
Cc:     davem@...emloft.net, netdev@...r.kernel.org
Subject: [PATCH 1/4] netfilter: nf_flow_table: fix big-endian integer overflow

From: Arnd Bergmann <arnd@...db.de>

In some configurations, gcc reports an integer overflow:

net/netfilter/nf_flow_table_offload.c: In function 'nf_flow_rule_match':
net/netfilter/nf_flow_table_offload.c:80:21: error: unsigned conversion from 'int' to '__be16' {aka 'short unsigned int'} changes value from '327680' to '0' [-Werror=overflow]
   mask->tcp.flags = TCP_FLAG_RST | TCP_FLAG_FIN;
                     ^~~~~~~~~~~~

>From what I can tell, we want the upper 16 bits of these constants,
so they need to be shifted in cpu-endian mode.

Fixes: c29f74e0df7a ("netfilter: nf_flow_table: hardware offload support")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/netfilter/nf_flow_table_offload.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
index de7a0d1e15c8..0d72e5ccb47b 100644
--- a/net/netfilter/nf_flow_table_offload.c
+++ b/net/netfilter/nf_flow_table_offload.c
@@ -88,7 +88,7 @@ static int nf_flow_rule_match(struct nf_flow_match *match,
 	switch (tuple->l4proto) {
 	case IPPROTO_TCP:
 		key->tcp.flags = 0;
-		mask->tcp.flags = TCP_FLAG_RST | TCP_FLAG_FIN;
+		mask->tcp.flags = cpu_to_be16(be32_to_cpu(TCP_FLAG_RST | TCP_FLAG_FIN) >> 16);
 		match->dissector.used_keys |= BIT(FLOW_DISSECTOR_KEY_TCP);
 		break;
 	case IPPROTO_UDP:
-- 
2.11.0