netdev - Re: [PATCH net-next] ipv6: Fix signed integer overflow in __ip6_append

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Date:   Mon, 23 May 2022 20:54:47 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     Wang Yufen <wangyufen@...wei.com>
Cc:     David Miller <davem@...emloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, netdev <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH net-next] ipv6: Fix signed integer overflow in __ip6_append_data

On Mon, May 23, 2022 at 8:29 PM Wang Yufen <wangyufen@...wei.com> wrote:
>
> Resurrect ubsan overflow checks and ubsan report this warning,
> fix it by change len check from INT_MAX to IPV6_MAXPLEN.
>
> UBSAN: signed-integer-overflow in net/ipv6/ip6_output.c:1489:19
> 2147479552 + 8567 cannot be represented in type 'int'

OK, so why not fix this point, instead of UDP, which is only one of
the possible callers ?

It seems the check in __ip6_append_data() should be unsigned.