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

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

[Chunfeng Yun]

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;
+
+	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;
 
+	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;
 
+	mep = to_mtu3_ep(ep);
 	mep->wedged = 1;
 
 	return usb_ep_set_halt(ep);
-- 
1.9.1
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Re: [PATCH v2] usb: mtu3: Fix NULL pointer dereferences

[Markus Elfring]

> Some pointers are dereferenced before successful checks.

I propose to reconsider and improve also this change description.

* Would a null pointer dereference be possible only with the variables “mep”
  and “mreq” in the implementation of the function “mtu3_gadget_dequeue”?
  (Can it make sense to split the patch according to this detail?)

* How do you think about to convert any more variable initialisations
  to later assignments?

* Will it become helpful to add the tag “Fixes” to the commit message?


…
> ---
> v2: nothing changed, but abandon another patch

Are there chances to take any previous patch review comments better into account
(besides the shown reduction of update steps)?


> ---
>  drivers/usb/mtu3/mtu3_gadget.c | 25 ++++++++++++++++++-------

I suggest to replace the triple dashes before this diffstat by a blank line.

Regards,
Markus

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

[Greg Kroah-Hartman]

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

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

[Chunfeng Yun]

On Wed, 2020-07-01 at 13:58 +0200, Greg Kroah-Hartman wrote:
> 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?
Yes, I find all class drivers already ensure they are not NULL.

> 
> > +
> > +	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?
Maybe when the class driver has something wrong:)

You mean it's better to remove these unnecessary checks?

Thanks

> 
> >  
> > +	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

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

[Felipe Balbi]

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Chunfeng Yun <chunfeng.yun@mediatek.com> writes:

> Some pointers are dereferenced before successful checks.
>
> Reported-by: Markus Elfring <Markus.Elfring@web.de>
> Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>

do you need a Fixes tag here? Perhaps a Cc stable too?

-- 
balbi

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

[Felipe Balbi]

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Hi,

Chunfeng Yun <chunfeng.yun@mediatek.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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Re: [V2 PATCH] usb: mtu3: fix NULL pointer dereference

[Chunfeng Yun]

On Thu, 2020-07-09 at 09:40 +0300, Felipe Balbi wrote:
> Chunfeng Yun <chunfeng.yun@mediatek.com> writes:
> 
> > Some pointers are dereferenced before successful checks.
> >
> > Reported-by: Markus Elfring <Markus.Elfring@web.de>
> > Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
> 
> do you need a Fixes tag here? Perhaps a Cc stable too?
It will not cause somes issues, I think no need add it.

According to Greg's comment, I guess he means no need check these
pointers at all, so I'll send a new version to remove checks.

Thank you

> 

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