Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.32 as permitted sender) client-ip=23.128.96.32;
MIME-Version: 1.0
References: <20231117152728.2286551-1-chentao@kylinos.cn>
In-Reply-To: <20231117152728.2286551-1-chentao@kylinos.cn>
From:   Eric Dumazet <edumazet@google.com>
Date:   Fri, 17 Nov 2023 18:15:08 +0100
Message-ID: <CANn89iLHd9oxO6yXmZMfO5cTsnSzqa==ZBCnNEySKpiH86q54Q@mail.gmail.com>
Subject: Re: [PATCH] ipv4: Correct/silence an endian warning in __ip_do_redirect
To:     Kunwu Chan <chentao@kylinos.cn>
Cc:     davem@davemloft.net, dsahern@kernel.org, kuba@kernel.org,
        pabeni@redhat.com, kunwu.chan@hotmail.com, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Fri, Nov 17, 2023 at 6:07=E2=80=AFPM Kunwu Chan <chentao@kylinos.cn> wro=
te:
>
> net/ipv4/route.c:783:46: warning: incorrect type in argument 2 (different=
 base types)
> net/ipv4/route.c:783:46:    expected unsigned int [usertype] key
> net/ipv4/route.c:783:46:    got restricted __be32 [usertype] new_gw
>
> Signed-off-by: Kunwu Chan <chentao@kylinos.cn>

We need Fixes: tag for networking patches.

> ---
>  net/ipv4/route.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/ipv4/route.c b/net/ipv4/route.c
> index 3290a4442b4a..e8a542c6b031 100644
> --- a/net/ipv4/route.c
> +++ b/net/ipv4/route.c
> @@ -780,7 +780,7 @@ static void __ip_do_redirect(struct rtable *rt, struc=
t sk_buff *skb, struct flow
>                         goto reject_redirect;
>         }
>
> -       n =3D __ipv4_neigh_lookup(rt->dst.dev, new_gw);
> +       n =3D __ipv4_neigh_lookup(rt->dst.dev, be32_to_cpu(new_gw));
>         if (!n)
>                 n =3D neigh_create(&arp_tbl, &new_gw, rt->dst.dev);
>         if (!IS_ERR(n)) {
> --
> 2.34.1
>

How was this patch tested ?

You are 'fixing' sparse warnings by replacing them with real bugs.

be32_to_cpu() is going to swap bytes on x86, so the lookup will fail horrib=
ly.

Here, if you must silence sparse, you want (__force u32)new_gw

Look at this commit for a template.

commit 3c42b2019863b327caa233072c50739d4144dd16