netdev - [PATCH net-next v2 2/5] udp_tunnel: fix compile warning

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Message-ID: <5c4df4171225ab664c748da190c6f2c2f662c48b.1742557254.git.pabeni@redhat.com>
Date: Fri, 21 Mar 2025 12:52:53 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: netdev@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Simon Horman <horms@...nel.org>,
	Willem de Bruijn <willemdebruijn.kernel@...il.com>,
	David Ahern <dsahern@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH net-next v2 2/5] udp_tunnel: fix compile warning

Nathan reported that the compiler is not happy to use a zero
size udp_tunnel_gro_types array:

  net/ipv4/udp_offload.c:130:8: warning: array index 0 is past the end of the array (that has type 'struct udp_tunnel_type_entry[0]') [-Warray-bounds]
    130 |                                    udp_tunnel_gro_types[0].gro_receive);
        |                                    ^                    ~
  include/linux/static_call.h:154:42: note: expanded from macro 'static_call_update'
    154 |         typeof(&STATIC_CALL_TRAMP(name)) __F = (func);                  \
        |                                                 ^~~~
  net/ipv4/udp_offload.c:47:1: note: array 'udp_tunnel_gro_types' declared here
     47 | static struct udp_tunnel_type_entry udp_tunnel_gro_types[UDP_MAX_TUNNEL_TYPES];
        | ^
  1 warning generated.

In such (unusual) configuration we should skip entirely the
static call optimization accounting.

Reported-by: syzbot+8c469a2260132cd095c1@...kaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/cover.1741718157.git.pabeni@redhat.com/T/#m6e309a49f04330de81a618c3c166368252ba42e4
Fixes: 311b36574ceac ("udp_tunnel: use static call for GRO hooks when possible")
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 net/ipv4/udp_offload.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 02365b818f1af..fd2b8e3830beb 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -83,7 +83,7 @@ void udp_tunnel_update_gro_rcv(struct sock *sk, bool add)
 	struct udp_sock *up = udp_sk(sk);
 	int i, old_gro_type_nr;
 
-	if (!up->gro_receive)
+	if (!UDP_MAX_TUNNEL_TYPES || !up->gro_receive)
 		return;
 
 	mutex_lock(&udp_tunnel_gro_type_lock);
-- 
2.48.1