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

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Date:	Mon, 11 Apr 2016 08:07:28 +0300
From:	Felipe Balbi <felipe.balbi@...ux.intel.com>
To:	chunfeng yun <chunfeng.yun@...iatek.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	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 ?

>> Shouldn't we fix that issue instead?
> I don't know which way is better, but it seems simple to fix it up in
> buffer.c 

I think we should, really, avoid a 0-length allocation, but passing a
size of 0 to testusb isn't very good either ;-) How are you calling
testusb ?

-- 
balbi

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