linux-kernel - Re: [PATCH v2] usb: dwc2: host: Fix use after free w/ simultaneous irqs

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Date:	Fri, 16 Oct 2015 07:57:36 +0000
From:	John Youn <John.Youn@...opsys.com>
To:	Doug Anderson <dianders@...omium.org>,
	John Youn <John.Youn@...opsys.com>
CC:	"balbi@...com" <balbi@...com>, Yunzhi Li <lyz@...k-chips.com>,
	Heiko Stübner <heiko@...ech.de>,
	"linux-rockchip@...ts.infradead.org" 
	<linux-rockchip@...ts.infradead.org>,
	Julius Werner <jwerner@...omium.org>,
	"gregory.herrero@...el.com" <gregory.herrero@...el.com>,
	"yousaf.kaukab@...el.com" <yousaf.kaukab@...el.com>,
	"dinguyen@...nsource.altera.com" <dinguyen@...nsource.altera.com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] usb: dwc2: host: Fix use after free w/ simultaneous
 irqs

On 10/15/2015 4:38 PM, Doug Anderson wrote:
> John,
> 
> On Thu, Oct 15, 2015 at 4:21 PM, John Youn <John.Youn@...opsys.com> wrote:
>> Passing a NULL qtd to some of the subcases will lead to a NULL
>> pointer dereference in that function or some function that it
>> calls.
>>
>> I think you could just check the qtd after each call and bail if
>> it's not ok.
> 
> I worry a little bit about ignoring an interrupt that we've already
> acknowledged, but if you think that's safer I can certainly change the
> patch.
> 

In terms of avoiding crashes it's probably safer.

Whether it is correct or not, I'm not sure. I need to review the
code more.

The question is: after the qtd has been freed, is anything the
other handlers do necessary? Might have to look at each case
separately.

John

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