netdev - Re: Bug in br_handle

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Message-ID: <6b5d5550-07b3-61d7-c3ad-ec31f17fa862@cumulusnetworks.com>
Date:   Fri, 15 Feb 2019 16:12:18 +0200
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     Tomas Paukrt <Tomas.Paukrt@...antech-bb.cz>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Cc:     "roopa@...ulusnetworks.com" <roopa@...ulusnetworks.com>
Subject: Re: Bug in br_handle_frame

On 15/02/2019 16:03, Tomas Paukrt wrote:
> Hi,
> 
> I have recently discovered that kernel 3.12.10 is occasionally crashing 
> due to NULL pointer dereference in function br_handle_frame when we 
> reconfigure the bridge, because function br_port_get_rcu returns NULL.
> 
> It is very hard for us to replicate this issue, because it happens about 
> once per month in our testing environment, but I have created the 
> attached patch. Can you please check it? The latest kernel seems to be 
> affected too.
> 
> Best regards
> 
> Tomas
> 

Hi,
That should not be possible, br_port_get_rcu() is a wrapper for
dev->rx_handler_data which in turn should always be present in case
rx_handler is called as can be seen in netdev_rx_handler_unregister().
Could you please share details about the crash and possibly a trace ?
Do you have any custom patches applied ?

Thanks,
 Nik