netdev - Re: [PATCH] tg3: Avoid NULL pointer dereference in tg3_get

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Date:   Thu, 5 Jan 2017 13:53:05 -0800
From:   Michael Chan <michael.chan@...adcom.com>
To:     David Miller <davem@...emloft.net>
Cc:     wangyufen@...wei.com, Siva Reddy Kallam <siva.kallam@...adcom.com>,
        "prashant.sreedharan@...adcom.com" <prashant@...adcom.com>,
        "michael.chan@...adcom.com" <mchan@...adcom.com>,
        Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] tg3: Avoid NULL pointer dereference in tg3_get_nstats()

On Thu, Jan 5, 2017 at 12:17 PM, David Miller <davem@...emloft.net> wrote:
> From: Michael Chan <michael.chan@...adcom.com>
> Date: Thu, 5 Jan 2017 12:04:13 -0800
>
>> But it looks like ndo_get_stats() can be called without rtnl lock from
>> net-procfs.c.  So it is possible that we'll read tp->hw_stats after it
>> has been freed.  For example, if we are reading /proc/net/dev and
>> closing tg3 at the same time.  David, is not taking rtnl_lock in
>> net-procfs.c by design?
>
> Probably not, that dev_get_stats() call probably should be surrounded
> by RTNL protection.
>
> Doing a quick grep on dev_get_stats() shows other call sites, most of
> which are using it to fetch slave device statistics from the get stats
> method of the parent.  Which should be ok.
>
> It appears that the vlan procfs code in net/8021q/vlanproc.c has a
> similar bug as net/core/net-procfs.c
>
> Maybe net/core/net-sysfs.c has the same issue as well, and perhaps also
> net/openvswitch/vport.c:ovs_vport_get_stats().
>

OK.  I will send a patch later today to add rtnl_lock to these callers.