linux-kernel - Re: [PATCH 5/6] staging: ozwpan: Increase farewell report size.

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Date:	Fri, 2 Aug 2013 12:00:44 +0100
From:	Rupesh Gujare <rupesh.gujare@...el.com>
To:	Dan Carpenter <dan.carpenter@...cle.com>
CC:	<devel@...uxdriverproject.org>, <gregkh@...uxfoundation.org>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/6] staging: ozwpan: Increase farewell report size.

On 02/08/13 11:27, Dan Carpenter wrote:
> On Thu, Aug 01, 2013 at 06:45:01PM +0100, Rupesh Gujare wrote:
>> Farewell report size can be bigger than one byte, increase array
>> size to accomodate maximum 32 bytes of farewell report.
>>
> Gar...  No.  This is not right.
>
> 1) There is no check limiting the size to 32 and it could be up to
>     253 bytes.
>
> 2) Use defines instead of magic numbers.
>
> 3) The oz_farewell struct is supposed to be a variable length struct
>     but the variable part is put in the middle.  It doesn't make any
>     sense to put the length of the variable size array after then end
>     of the array because we can never find it again!  Put the
>     variable size array at the end.  Make it a zero length array.
>     u8 len;
>     u8 report[0];
>
> 4) In oz_add_farewell() we do this:
>
> 	f = kmalloc(sizeof(struct oz_farewell) + len - 1, GFP_ATOMIC);
>
>      The "- 1" refers to sizeof(f->report) but because it was a magic
>      number then it was missed when the sizeof(f->report) changed.
>
> 5) In [patch 6/6] we set the ->len member.  But because it is at the
>     end of a variable length array with no limit check the remote
>     attacker can just rewrite it using the memcpy() on the next line.
>
>
Thanks Dan.

A patch follows to fix above issues.

-- 
Regards,
Rupesh Gujare

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