netdev - Re: Several races in "usbnet" module (kernel 4.1.x)

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Message-ID: <55B0D27E.8090701@rosalab.ru>
Date:	Thu, 23 Jul 2015 14:39:42 +0300
From:	Eugene Shatokhin <eugene.shatokhin@...alab.ru>
To:	Oliver Neukum <oneukum@...e.com>
Cc:	netdev@...r.kernel.org, linux-usb@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Several races in "usbnet" module (kernel 4.1.x)

23.07.2015 12:43, Oliver Neukum пишет:
> On Mon, 2015-07-20 at 21:13 +0300, Eugene Shatokhin wrote:
>> [Race #5]
>>
>> Race on dev->rx_urb_size. I reproduced it a similar way as the races
>> #2
>> and #3 (changing MTU while downloading files).
>>
>> dev->rx_urb_size is written to here:
>> #0  usbnet_change_mtu (usbnet.c:392)
>>          dev->rx_urb_size = dev->hard_mtu;
>>
>> Here is the conflicting read from dev->rx_urb_size:
>> * rx_submit (usbnet.c:467)
>>          size_t                  size = dev->rx_urb_size;
>
> Yes, but what is the actual bad race? I mean, if you change
> the MTU in operation, there will be a race. That is just
> unavoidable.
> Do we generate errors?

No, I have observed no problems due to this race so far.

Regards,
Eugene



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