linux-kernel - Re: [V2 PATCH] usb: mtu3: fix NULL pointer dereference

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Date:   Thu, 09 Jul 2020 09:42:56 +0300
From:   Felipe Balbi <balbi@...nel.org>
To:     Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Felipe Balbi <felipe.balbi@...ux.intel.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Markus Elfring <Markus.Elfring@....de>,
        linux-usb@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [V2 PATCH] usb: mtu3: fix NULL pointer dereference


Hi,

Chunfeng Yun <chunfeng.yun@...iatek.com> writes:
>> > @@ -373,8 +380,8 @@ static int mtu3_gadget_dequeue(struct usb_ep *ep, struct usb_request *req)
>> >   */
>> >  static int mtu3_gadget_ep_set_halt(struct usb_ep *ep, int value)
>> >  {
>> > -	struct mtu3_ep *mep = to_mtu3_ep(ep);
>> > -	struct mtu3 *mtu = mep->mtu;
>> > +	struct mtu3_ep *mep;
>> > +	struct mtu3 *mtu;
>> >  	struct mtu3_request *mreq;
>> >  	unsigned long flags;
>> >  	int ret = 0;
>> > @@ -382,6 +389,9 @@ static int mtu3_gadget_ep_set_halt(struct usb_ep *ep, int value)
>> >  	if (!ep)
>> >  		return -EINVAL;
>> 
>> Same here, how can that ever happen?
> Maybe when the class driver has something wrong:)
>
> You mean it's better to remove these unnecessary checks?

if we need those checks, I'd rather have them at a central location,
such as udc/core.c. But, as Greg mentioned, the kernel doesn't call
these with NULL pointers.

-- 
balbi

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