linux-kernel - Re: [Security] Should open TTY device files pin minor numbers?

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Date:	Wed, 29 Jul 2009 14:20:51 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Greg KH <greg@...ah.com>
CC:	Alan Stern <stern@...land.harvard.edu>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	alan@...rguk.ukuu.org.uk
Subject: Re: [Security] Should open TTY device files pin minor numbers?

On 07/24/2009 10:14 PM, Greg KH wrote:
> On Thu, Jul 23, 2009 at 02:38:01PM -0400, Alan Stern wrote:
>> Recent work in the TTY core and in usb-serial has caused a change 
>> in behavior between 2.6.30 and 2.6.31-rc.  Namely, if a USB serial 
>> device is unplugged while a process holds the device file open, the 
>> minor number won't get reused until the process closes the file.
> 
> That's how the usb-serial code always worked, this is nothing new at
> all.
> 
>> For example, if you run minicom over /dev/ttyUSB0, unplug the USB
>> device while minicom is running, and then plug it in again before
>> exiting minicom, it will reappear as /dev/ttyUSB1 instead of
>> /dev/ttyUSB0 (which will be gone).
> 
> Exactly.  People are used to this by now, it shouldn't be a supprise :)
> 

It is, however, a *very* nasty surprise when the USB bus glitches.

	-hpa
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