netdev - Re: BROKEN Re: [PATCH] netlink: 2-clause nla

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Date:   Mon, 05 Dec 2016 16:09:13 +0100
From:   Johannes Berg <johannes@...solutions.net>
To:     Alexey Dobriyan <adobriyan@...il.com>,
        David Miller <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>
Subject: Re: BROKEN Re: [PATCH] netlink: 2-clause nla_ok()

> Maybe someone could vouch that other checks prevent
> this kind of situation from happening but not me.

No, now that you spell it out (and I see the patch) - this is
absolutely needed because nla_for_each_attr() [1] can be called on
arbitrary data coming from userspace in a message, e.g. by way
of nla_for_each_nested(). Even if it's not malformed, nla_ok() is the
only abort condition for that loop, so it would read at least one
nla_len after the real buffer without that condition.

johannes

[1] which seems to be the only significant user thereof