netdev - Suspicious pattern for use of function xt_register

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Date:   Mon, 23 Aug 2021 19:01:14 +0200
From:   Lukas Bulwahn <lukas.bulwahn@...il.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>,
        netfilter-devel@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Netdev <netdev@...r.kernel.org>, coreteam@...filter.org,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Suspicious pattern for use of function xt_register_template()

Dear Florian, dear netfilter maintainers,

Commit fdacd57c79b ("netfilter: x_tables: never register tables by
default") on linux-next
introduces the function xt_register_template() and in all cases but
one, the calls to that function are followed by:

    if (ret < 0)
        return ret;

All these checks were also added with the commit above.

In the one case, for iptable_mangle_init() in
./net/ipv4/netfilter/iptable_mangle.c, this pattern was not followed.
This makes this ret assignment in this function a Dead Store and
hence, clang-analyzer warns about that.

Are we missing here an early return for a negative return value as
well, or is this case for iptable_mangle_init() in
./net/ipv4/netfilter/iptable_mangle.c special?

Best regards,

Lukas