netdev - Re: [PATCH net] pppoe: check sockaddr length in pppoe

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Date:   Fri, 27 Apr 2018 12:01:18 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     g.nault@...halink.fr
Cc:     kevin@...rana.org, netdev@...r.kernel.org, mostrows@...thlink.net
Subject: Re: [PATCH net] pppoe: check sockaddr length in pppoe_connect()

From: Guillaume Nault <g.nault@...halink.fr>
Date: Fri, 27 Apr 2018 17:39:06 +0200

> Thanks for the suggestion. But ->sa_family has never been checked.
> Therefore, it has always been possible to connect a PPPoE or L2TP
> socket with an invalid .sa_family field. I'd be surprised if there were
> implementations relying on that, but we never know (for example, an
> implementation could send this field uninitialised). By being stricter
> we'd break such programs. And we don't need this field in the
> connection process, so not checking its value doesn't harm.
> 
> I'm all for being strict and validating user-provided data as much as
> possible, but I'm afraid its too late in this case.

Agreed, adding the check is too risky.