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

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Message-ID: <1437644594.4377.12.camel@suse.com>
Date:	Thu, 23 Jul 2015 11:43:14 +0200
From:	Oliver Neukum <oneukum@...e.com>
To:	Eugene Shatokhin <eugene.shatokhin@...alab.ru>
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)

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?

	Regards
		Oliver


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