netdev - NETLINK_URELEASE non-bound socket problem (was: [PATCH] Fix local DoS in cfg80211 subsystem)

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Message-ID: <1459850188.18188.38.camel@sipsolutions.net>
Date:	Tue, 05 Apr 2016 11:56:28 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	Dmitrijs Ivanovs <dmitrijs.ivanovs@...t.com>,
	linux-wireless@...r.kernel.org
Cc:	netdev <netdev@...r.kernel.org>, samuel <samuel@...tiz.org>,
	Pablo Neira Ayuso <pablo@...filter.org>,
	Thomas Graf <tgraf@...g.ch>
Subject: NETLINK_URELEASE non-bound socket problem (was: [PATCH] Fix local
 DoS in cfg80211 subsystem)

Hi Dmitrijs,

Thanks for reporting this problem.

> The patch below corrects this problem in kernel space. 

I don't think that this is correct, there are four more users of
NETLINK_URELEASE (nfnetlink, NFC), and afaict all of them have the same
bug as nl80211.

Rather than fix all of them, I think we should simply not report
NETLINK_URELEASE for netlink sockets that weren't bound; if any user
comes up that requires them later we could add a new event instead.

I can't find what commit introduced this code, it goes back before git
history, so I don't have the commit log. Maybe it was done for
nfnetlink log/queue? Certainly both nl80211 and NFC are much newer.

> Also, it is
> recommended to ensure that user-space applications are not using
> user-supplied port_id for netlink sockets (which is default in
> libnl-tiny for example).

This I think we should remove from the commit log - it's misleading and
there's no point.

johannes