netdev - Re: NULL pointer dereference in veth_stats

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Message-ID: <1357327406.1678.2139.camel@edumazet-glaptop>
Date:	Fri, 04 Jan 2013 11:23:26 -0800
From:	Eric Dumazet <erdnetdev@...il.com>
To:	Ben Hutchings <bhutchings@...arflare.com>
Cc:	Tom Parkin <tparkin@...alix.com>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>
Subject: Re: NULL pointer dereference in veth_stats_one

On Fri, 2013-01-04 at 18:17 +0000, Ben Hutchings wrote:

> This possibly needs some memory barriers to properly synchronise with
> veth_newlink().  But can you not move initialisation of the peer
> pointers before registration of the devices in veth_newlink(), so that
> veth_get_stats64() cannot be called before they are initialised?

The ->peer pointer cannot change once set. ( its never cleared )

So the problem would not be in veth_newlink(), but might be in
veth_dellink()

It seems we would have a problem in veth_get_ethtool_stats() already...

More generally, what prevents a get_stats() being called while a
dellink() (-> veth_dev_free() -> free_percpu()) is done ?

(Same thing is done for tunnel/dummy stats percpu data)


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