linux-kernel - Re: [PATCH] usb: core: buffer: avoid NULL pointer dereferrence

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Date:	Mon, 11 Apr 2016 11:24:22 +0300
From:	Felipe Balbi <felipe.balbi@...ux.intel.com>
To:	chunfeng yun <chunfeng.yun@...iatek.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-usb@...r.kernel.org, linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] usb: core: buffer: avoid NULL pointer dereferrence


Hi,

chunfeng yun <chunfeng.yun@...iatek.com> writes:
>> > On Fri, 2016-04-08 at 07:07 -0700, Greg Kroah-Hartman wrote:
>> >> On Fri, Apr 08, 2016 at 05:08:03PM +0800, Chunfeng Yun wrote:
>> >> > NULL pointer dereferrence will happen when class driver
>> >> > wants to allocate zero length buffer and pool_max[0]
>> >> > can't be used, so skip reserved pool in this case.
>> >> 
>> >> Why would a driver want to allocate a 0 length buffer?  What driver does
>> >> this?
>> > It's misc/usbtest.c
>> 
>> that'll do what you ask it to do with the userspace tool testusb. Are
>> you trying to pass a size of 0 ?
>> 
> No, I just ran "testusb -t10" which called test_ctrl_queue().
> In this function, sub-case 8 passed a parameter @len as 0 to
> simple_alloc_urb(), and then it tried to allocate a 0-length buffer.

odd, I have never seen this problem running testusb with the same
arguments.

-- 
balbi

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