linux-kernel - Re: [PATCH 090/173] USB: serial/kobil_sct, fix potential tty NULL dereference

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Date:	Wed, 27 Apr 2011 00:01:07 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	Willy Tarreau <w@....eu>
CC:	linux-kernel@...r.kernel.org, stable@...nel.org,
	stable-review@...nel.org, Alan Cox <alan@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: Re: [PATCH 090/173] USB: serial/kobil_sct, fix potential tty NULL
 dereference

On 04/26/2011 09:53 PM, Willy Tarreau wrote:
> On Tue, Apr 26, 2011 at 12:07:07PM +0200, Jiri Slaby wrote:
>> On 04/25/2011 10:04 PM, Willy Tarreau wrote:
>>> 2.6.27.59-stable review patch.  If anyone has any objections, please let
>>> us know.
>>>
>>> ------------------
>>>
>>> From: Jiri Slaby<jslaby@...e.cz>
>>>
>>> commit 6960f40a954619857e7095a6179eef896f297077 upstream.
>>>
>>> Make sure that we check the return value of tty_port_tty_get.
>>> Sometimes it may return NULL and we later dereference that.
>>>
>>> The only place here is in kobil_read_int_callback, so fix it.
>>>
>>> Signed-off-by: Jiri Slaby<jslaby@...e.cz>
>>> Cc: Alan Cox<alan@...ux.intel.com>
>>> Signed-off-by: Greg Kroah-Hartman<gregkh@...e.de>
>>>
>>> ---
>>>   drivers/usb/serial/kobil_sct.c |    2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> --- a/drivers/usb/serial/kobil_sct.c
>>> +++ b/drivers/usb/serial/kobil_sct.c
>>> @@ -372,7 +372,7 @@ static void kobil_read_int_callback(stru
>>>   	}
>>>
>>>   	tty = port->port.tty;
>>> -	if (urb->actual_length) {
>>> +	if (tty&&   urb->actual_length) {
>>
>> Ok, but this doesn't fix the bug (the URB should be killed or something
>> similar in that kernel), it only makes the window smaller.
>
> OK I get it now, it requires patch 4a90f09b which is quite not some
> suitable material for -longterm.

Yeah and perhaps some other changes (like adding hangup support).

> Do you think it's better to completely remove this patch than making
> one think the risk of bug is gone while it is not ? Unless we find
> something more reliable, I'd rather drop the patch.

To be honest I don't know what's better :). Maybe I would incline to the 
drop-it side, but leaving up to you.

thanks,
-- 
js
suse labs
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