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

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Message-ID: <20200701115821.GA2184169@kroah.com>
Date:   Wed, 1 Jul 2020 13:58:21 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Chunfeng Yun <chunfeng.yun@...iatek.com>
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

On Tue, Jun 30, 2020 at 03:42:22PM +0800, Chunfeng Yun wrote:
> Some pointers are dereferenced before successful checks.
> 
> Reported-by: Markus Elfring <Markus.Elfring@....de>
> Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
> ---
> v2: nothing changed, but abandon another patch
> ---
>  drivers/usb/mtu3/mtu3_gadget.c | 25 ++++++++++++++++++-------
>  1 file changed, 18 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/usb/mtu3/mtu3_gadget.c b/drivers/usb/mtu3/mtu3_gadget.c
> index f93732e..1689ca8 100644
> --- a/drivers/usb/mtu3/mtu3_gadget.c
> +++ b/drivers/usb/mtu3/mtu3_gadget.c
> @@ -332,14 +332,21 @@ static int mtu3_gadget_queue(struct usb_ep *ep,
>  
>  static int mtu3_gadget_dequeue(struct usb_ep *ep, struct usb_request *req)
>  {
> -	struct mtu3_ep *mep = to_mtu3_ep(ep);
> -	struct mtu3_request *mreq = to_mtu3_request(req);
> +	struct mtu3_ep *mep;
> +	struct mtu3_request *mreq;
>  	struct mtu3_request *r;
> +	struct mtu3 *mtu;
>  	unsigned long flags;
>  	int ret = 0;
> -	struct mtu3 *mtu = mep->mtu;
>  
> -	if (!ep || !req || mreq->mep != mep)
> +	if (!ep || !req)
> +		return -EINVAL;

How will either of those ever be NULL?  The kernel will not call this
function with either of them being NULL, right?

> +
> +	mep = to_mtu3_ep(ep);
> +	mtu = mep->mtu;
> +
> +	mreq = to_mtu3_request(req);
> +	if (mreq->mep != mep)
>  		return -EINVAL;
>  
>  	dev_dbg(mtu->dev, "%s : req=%p\n", __func__, req);
> @@ -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?

>  
> +	mep = to_mtu3_ep(ep);
> +	mtu = mep->mtu;
> +
>  	dev_dbg(mtu->dev, "%s : %s...", __func__, ep->name);
>  
>  	spin_lock_irqsave(&mtu->lock, flags);
> @@ -422,11 +432,12 @@ static int mtu3_gadget_ep_set_halt(struct usb_ep *ep, int value)
>  /* Sets the halt feature with the clear requests ignored */
>  static int mtu3_gadget_ep_set_wedge(struct usb_ep *ep)
>  {
> -	struct mtu3_ep *mep = to_mtu3_ep(ep);
> +	struct mtu3_ep *mep;
>  
>  	if (!ep)
>  		return -EINVAL;

Again, same here.

thanks,

greg k-h