linux-kernel - Re: [patch net] macvlan: fix passthru mode race between dev removal and rx path

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Message-Id: <20130511.162554.1852680841693318294.davem@davemloft.net>
Date:	Sat, 11 May 2013 16:25:54 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	jiri@...nulli.us
Cc:	netdev@...r.kernel.org, sri@...ibm.com, kaber@...sh.net,
	linux-kernel@...r.kernel.org, mtesar@...hat.com,
	eric.dumazet@...il.com
Subject: Re: [patch net] macvlan: fix passthru mode race between dev
 removal and rx path

From: Jiri Pirko <jiri@...nulli.us>
Date: Thu,  9 May 2013 16:23:40 +0200

> Currently, if macvlan in passthru mode is created and data are rxed and
> you remove this device, following panic happens:
> 
> NULL pointer dereference at 0000000000000198
> IP: [<ffffffffa0196058>] macvlan_handle_frame+0x153/0x1f7 [macvlan]
> 
> I'm using following script to trigger this:
 ...
> I run this script while "ping -f" is running on another machine to send
> packets to e1 rx.
> 
> Reason of the panic is that list_first_entry() is blindly called in
> macvlan_handle_frame() even if the list was empty. vlan is set to
> incorrect pointer which leads to the crash.
> 
> I'm fixing this by protecting port->vlans list by rcu and by preventing
> from getting incorrect pointer in case the list is empty.
> 
> Introduced by: commit eb06acdc85585f2 "macvlan: Introduce 'passthru' mode to takeover the underlying device"
> 
> Signed-off-by: Jiri Pirko <jiri@...nulli.us>

Applied and queued up for -stable, thanks!
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