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

Greg Kroah-Hartman
2020-07-01T11:58:37Z

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@web.de>
> Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.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