diff mbox series

[1/3] usb: gadget: f_hid: fix f_hidg lifetime vs cdev

Message ID 20221122123523.3068034-2-john@metanate.com
State New
Headers
Series usb: gadget: f_hid: fix f_hidg lifetime vs cdev |

Commit Message

John Keeping Nov. 22, 2022, 12:35 p.m. UTC 
  The embedded struct cdev does not have its lifetime correctly tied to
the enclosing struct f_hidg, so there is a use-after-free if /dev/hidgN
is held open while the gadget is deleted.

This can readily be replicated with libusbgx's example programs (for
conciseness - operating directly via configfs is equivalent):

	gadget-hid
	exec 3<> /dev/hidg0
	gadget-vid-pid-remove
	exec 3<&-

Pull the existing device up in to struct f_hidg and make use of the
cdev_device_{add,del}() helpers.  This changes the lifetime of the
device object to match struct f_hidg, but note that it is still added
and deleted at the same time.

Fixes: 71adf1189469 ("USB: gadget: add HID gadget driver")
Signed-off-by: John Keeping <john@metanate.com>
---
 drivers/usb/gadget/function/f_hid.c | 52 ++++++++++++++++-------------
 1 file changed, 28 insertions(+), 24 deletions(-)

Comments

Andrzej Pietrasiewicz Nov. 23, 2022, 11:52 a.m. UTC | #1 
Hi John,

W dniu 22.11.2022 o 13:35, John Keeping pisze:
> The embedded struct cdev does not have its lifetime correctly tied to
> the enclosing struct f_hidg, so there is a use-after-free if /dev/hidgN
> is held open while the gadget is deleted.
> 
> This can readily be replicated with libusbgx's example programs (for
> conciseness - operating directly via configfs is equivalent):
> 
> 	gadget-hid
> 	exec 3<> /dev/hidg0
> 	gadget-vid-pid-remove
> 	exec 3<&-
> 
> Pull the existing device up in to struct f_hidg and make use of the
> cdev_device_{add,del}() helpers.  This changes the lifetime of the
> device object to match struct f_hidg, but note that it is still added
> and deleted at the same time.
> 
> Fixes: 71adf1189469 ("USB: gadget: add HID gadget driver")
> Signed-off-by: John Keeping <john@metanate.com>
> ---
>   drivers/usb/gadget/function/f_hid.c | 52 ++++++++++++++++-------------
>   1 file changed, 28 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/usb/gadget/function/f_hid.c b/drivers/usb/gadget/function/f_hid.c
> index ca0a7d9eaa34..8b8bbeaa27cb 100644
> --- a/drivers/usb/gadget/function/f_hid.c
> +++ b/drivers/usb/gadget/function/f_hid.c
> @@ -71,7 +71,7 @@ struct f_hidg {
>   	wait_queue_head_t		write_queue;
>   	struct usb_request		*req;
>   
> -	int				minor;
> +	struct device			dev;
>   	struct cdev			cdev;
>   	struct usb_function		func;
>   
> @@ -84,6 +84,14 @@ static inline struct f_hidg *func_to_hidg(struct usb_function *f)
>   	return container_of(f, struct f_hidg, func);
>   }
>   
> +static void hidg_release(struct device *dev)
> +{
> +	struct f_hidg *hidg = container_of(dev, struct f_hidg, dev);
> +
> +	kfree(hidg->set_report_buf);
> +	kfree(hidg);
> +}
> +

I assume the above is supposed to free the hidg memory as a result of
put_device() and you free two things here ...

>   /*-------------------------------------------------------------------------*/
>   /*                           Static descriptors                            */
>   
> @@ -904,9 +912,7 @@ static int hidg_bind(struct usb_configuration *c, struct usb_function *f)
>   	struct usb_ep		*ep;
>   	struct f_hidg		*hidg = func_to_hidg(f);
>   	struct usb_string	*us;
> -	struct device		*device;
>   	int			status;
> -	dev_t			dev;
>   
>   	/* maybe allocate device-global string IDs, and patch descriptors */
>   	us = usb_gstrings_attach(c->cdev, ct_func_strings,
> @@ -999,21 +1005,11 @@ static int hidg_bind(struct usb_configuration *c, struct usb_function *f)
>   
>   	/* create char device */
>   	cdev_init(&hidg->cdev, &f_hidg_fops);
> -	dev = MKDEV(major, hidg->minor);
> -	status = cdev_add(&hidg->cdev, dev, 1);
> +	status = cdev_device_add(&hidg->cdev, &hidg->dev);
>   	if (status)
>   		goto fail_free_descs;
>   
> -	device = device_create(hidg_class, NULL, dev, NULL,
> -			       "%s%d", "hidg", hidg->minor);
> -	if (IS_ERR(device)) {
> -		status = PTR_ERR(device);
> -		goto del;
> -	}
> -
>   	return 0;
> -del:
> -	cdev_del(&hidg->cdev);
>   fail_free_descs:
>   	usb_free_all_descriptors(f);
>   fail:
> @@ -1244,9 +1240,7 @@ static void hidg_free(struct usb_function *f)
>   
>   	hidg = func_to_hidg(f);
>   	opts = container_of(f->fi, struct f_hid_opts, func_inst);
> -	kfree(hidg->report_desc);
> -	kfree(hidg->set_report_buf);
> -	kfree(hidg);

... while here 3 things used to be freed. What happens to hidg->report_desc?

Regards,

Andrzej
John Keeping Nov. 23, 2022, 12:03 p.m. UTC | #2 
On Wed, Nov 23, 2022 at 12:52:24PM +0100, Andrzej Pietrasiewicz wrote:
> Hi John,
> 
> W dniu 22.11.2022 o 13:35, John Keeping pisze:
> > The embedded struct cdev does not have its lifetime correctly tied to
> > the enclosing struct f_hidg, so there is a use-after-free if /dev/hidgN
> > is held open while the gadget is deleted.
> > 
> > This can readily be replicated with libusbgx's example programs (for
> > conciseness - operating directly via configfs is equivalent):
> > 
> > 	gadget-hid
> > 	exec 3<> /dev/hidg0
> > 	gadget-vid-pid-remove
> > 	exec 3<&-
> > 
> > Pull the existing device up in to struct f_hidg and make use of the
> > cdev_device_{add,del}() helpers.  This changes the lifetime of the
> > device object to match struct f_hidg, but note that it is still added
> > and deleted at the same time.
> > 
> > Fixes: 71adf1189469 ("USB: gadget: add HID gadget driver")
> > Signed-off-by: John Keeping <john@metanate.com>
> > ---
> >   drivers/usb/gadget/function/f_hid.c | 52 ++++++++++++++++-------------
> >   1 file changed, 28 insertions(+), 24 deletions(-)
> > 
> > diff --git a/drivers/usb/gadget/function/f_hid.c b/drivers/usb/gadget/function/f_hid.c
> > index ca0a7d9eaa34..8b8bbeaa27cb 100644
> > --- a/drivers/usb/gadget/function/f_hid.c
> > +++ b/drivers/usb/gadget/function/f_hid.c
> > @@ -71,7 +71,7 @@ struct f_hidg {
> >   	wait_queue_head_t		write_queue;
> >   	struct usb_request		*req;
> > -	int				minor;
> > +	struct device			dev;
> >   	struct cdev			cdev;
> >   	struct usb_function		func;
> > @@ -84,6 +84,14 @@ static inline struct f_hidg *func_to_hidg(struct usb_function *f)
> >   	return container_of(f, struct f_hidg, func);
> >   }
> > +static void hidg_release(struct device *dev)
> > +{
> > +	struct f_hidg *hidg = container_of(dev, struct f_hidg, dev);
> > +
> > +	kfree(hidg->set_report_buf);
> > +	kfree(hidg);
> > +}
> > +
> 
> I assume the above is supposed to free the hidg memory as a result of
> put_device() and you free two things here ...
> 
> >   /*-------------------------------------------------------------------------*/
> >   /*                           Static descriptors                            */
> > @@ -904,9 +912,7 @@ static int hidg_bind(struct usb_configuration *c, struct usb_function *f)
> >   	struct usb_ep		*ep;
> >   	struct f_hidg		*hidg = func_to_hidg(f);
> >   	struct usb_string	*us;
> > -	struct device		*device;
> >   	int			status;
> > -	dev_t			dev;
> >   	/* maybe allocate device-global string IDs, and patch descriptors */
> >   	us = usb_gstrings_attach(c->cdev, ct_func_strings,
> > @@ -999,21 +1005,11 @@ static int hidg_bind(struct usb_configuration *c, struct usb_function *f)
> >   	/* create char device */
> >   	cdev_init(&hidg->cdev, &f_hidg_fops);
> > -	dev = MKDEV(major, hidg->minor);
> > -	status = cdev_add(&hidg->cdev, dev, 1);
> > +	status = cdev_device_add(&hidg->cdev, &hidg->dev);
> >   	if (status)
> >   		goto fail_free_descs;
> > -	device = device_create(hidg_class, NULL, dev, NULL,
> > -			       "%s%d", "hidg", hidg->minor);
> > -	if (IS_ERR(device)) {
> > -		status = PTR_ERR(device);
> > -		goto del;
> > -	}
> > -
> >   	return 0;
> > -del:
> > -	cdev_del(&hidg->cdev);
> >   fail_free_descs:
> >   	usb_free_all_descriptors(f);
> >   fail:
> > @@ -1244,9 +1240,7 @@ static void hidg_free(struct usb_function *f)
> >   	hidg = func_to_hidg(f);
> >   	opts = container_of(f->fi, struct f_hid_opts, func_inst);
> > -	kfree(hidg->report_desc);
> > -	kfree(hidg->set_report_buf);
> > -	kfree(hidg);
> 
> ... while here 3 things used to be freed. What happens to hidg->report_desc?

This switched to devm to simplify error handling in hidg_alloc().
Andrzej Pietrasiewicz Nov. 23, 2022, 12:20 p.m. UTC | #3 
W dniu 23.11.2022 o 13:03, John Keeping pisze:
> On Wed, Nov 23, 2022 at 12:52:24PM +0100, Andrzej Pietrasiewicz wrote:
>> Hi John,
>>
>> W dniu 22.11.2022 o 13:35, John Keeping pisze:
>>> The embedded struct cdev does not have its lifetime correctly tied to
>>> the enclosing struct f_hidg, so there is a use-after-free if /dev/hidgN
>>> is held open while the gadget is deleted.
>>>
>>> This can readily be replicated with libusbgx's example programs (for
>>> conciseness - operating directly via configfs is equivalent):
>>>
>>> 	gadget-hid
>>> 	exec 3<> /dev/hidg0
>>> 	gadget-vid-pid-remove
>>> 	exec 3<&-
>>>
>>> Pull the existing device up in to struct f_hidg and make use of the
>>> cdev_device_{add,del}() helpers.  This changes the lifetime of the
>>> device object to match struct f_hidg, but note that it is still added
>>> and deleted at the same time.
>>>
>>> Fixes: 71adf1189469 ("USB: gadget: add HID gadget driver")
>>> Signed-off-by: John Keeping <john@metanate.com>
>>> ---
>>>    drivers/usb/gadget/function/f_hid.c | 52 ++++++++++++++++-------------
>>>    1 file changed, 28 insertions(+), 24 deletions(-)
>>>
>>> diff --git a/drivers/usb/gadget/function/f_hid.c b/drivers/usb/gadget/function/f_hid.c
>>> index ca0a7d9eaa34..8b8bbeaa27cb 100644
>>> --- a/drivers/usb/gadget/function/f_hid.c
>>> +++ b/drivers/usb/gadget/function/f_hid.c
>>> @@ -71,7 +71,7 @@ struct f_hidg {
>>>    	wait_queue_head_t		write_queue;
>>>    	struct usb_request		*req;
>>> -	int				minor;
>>> +	struct device			dev;
>>>    	struct cdev			cdev;
>>>    	struct usb_function		func;
>>> @@ -84,6 +84,14 @@ static inline struct f_hidg *func_to_hidg(struct usb_function *f)
>>>    	return container_of(f, struct f_hidg, func);
>>>    }
>>> +static void hidg_release(struct device *dev)
>>> +{
>>> +	struct f_hidg *hidg = container_of(dev, struct f_hidg, dev);
>>> +
>>> +	kfree(hidg->set_report_buf);
>>> +	kfree(hidg);
>>> +}
>>> +
>>
>> I assume the above is supposed to free the hidg memory as a result of
>> put_device() and you free two things here ...
>>
>>>    /*-------------------------------------------------------------------------*/
>>>    /*                           Static descriptors                            */
>>> @@ -904,9 +912,7 @@ static int hidg_bind(struct usb_configuration *c, struct usb_function *f)
>>>    	struct usb_ep		*ep;
>>>    	struct f_hidg		*hidg = func_to_hidg(f);
>>>    	struct usb_string	*us;
>>> -	struct device		*device;
>>>    	int			status;
>>> -	dev_t			dev;
>>>    	/* maybe allocate device-global string IDs, and patch descriptors */
>>>    	us = usb_gstrings_attach(c->cdev, ct_func_strings,
>>> @@ -999,21 +1005,11 @@ static int hidg_bind(struct usb_configuration *c, struct usb_function *f)
>>>    	/* create char device */
>>>    	cdev_init(&hidg->cdev, &f_hidg_fops);
>>> -	dev = MKDEV(major, hidg->minor);
>>> -	status = cdev_add(&hidg->cdev, dev, 1);
>>> +	status = cdev_device_add(&hidg->cdev, &hidg->dev);
>>>    	if (status)
>>>    		goto fail_free_descs;
>>> -	device = device_create(hidg_class, NULL, dev, NULL,
>>> -			       "%s%d", "hidg", hidg->minor);
>>> -	if (IS_ERR(device)) {
>>> -		status = PTR_ERR(device);
>>> -		goto del;
>>> -	}
>>> -
>>>    	return 0;
>>> -del:
>>> -	cdev_del(&hidg->cdev);
>>>    fail_free_descs:
>>>    	usb_free_all_descriptors(f);
>>>    fail:
>>> @@ -1244,9 +1240,7 @@ static void hidg_free(struct usb_function *f)
>>>    	hidg = func_to_hidg(f);
>>>    	opts = container_of(f->fi, struct f_hid_opts, func_inst);
>>> -	kfree(hidg->report_desc);
>>> -	kfree(hidg->set_report_buf);
>>> -	kfree(hidg);
>>
>> ... while here 3 things used to be freed. What happens to hidg->report_desc?
> 
> This switched to devm to simplify error handling in hidg_alloc().

Ah, right!

Reviewed-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
diff mbox series

Patch

diff --git a/drivers/usb/gadget/function/f_hid.c b/drivers/usb/gadget/function/f_hid.c
index ca0a7d9eaa34..8b8bbeaa27cb 100644
--- a/drivers/usb/gadget/function/f_hid.c
+++ b/drivers/usb/gadget/function/f_hid.c
@@ -71,7 +71,7 @@  struct f_hidg {
 	wait_queue_head_t		write_queue;
 	struct usb_request		*req;
 
-	int				minor;
+	struct device			dev;
 	struct cdev			cdev;
 	struct usb_function		func;
 
@@ -84,6 +84,14 @@  static inline struct f_hidg *func_to_hidg(struct usb_function *f)
 	return container_of(f, struct f_hidg, func);
 }
 
+static void hidg_release(struct device *dev)
+{
+	struct f_hidg *hidg = container_of(dev, struct f_hidg, dev);
+
+	kfree(hidg->set_report_buf);
+	kfree(hidg);
+}
+
 /*-------------------------------------------------------------------------*/
 /*                           Static descriptors                            */
 
@@ -904,9 +912,7 @@  static int hidg_bind(struct usb_configuration *c, struct usb_function *f)
 	struct usb_ep		*ep;
 	struct f_hidg		*hidg = func_to_hidg(f);
 	struct usb_string	*us;
-	struct device		*device;
 	int			status;
-	dev_t			dev;
 
 	/* maybe allocate device-global string IDs, and patch descriptors */
 	us = usb_gstrings_attach(c->cdev, ct_func_strings,
@@ -999,21 +1005,11 @@  static int hidg_bind(struct usb_configuration *c, struct usb_function *f)
 
 	/* create char device */
 	cdev_init(&hidg->cdev, &f_hidg_fops);
-	dev = MKDEV(major, hidg->minor);
-	status = cdev_add(&hidg->cdev, dev, 1);
+	status = cdev_device_add(&hidg->cdev, &hidg->dev);
 	if (status)
 		goto fail_free_descs;
 
-	device = device_create(hidg_class, NULL, dev, NULL,
-			       "%s%d", "hidg", hidg->minor);
-	if (IS_ERR(device)) {
-		status = PTR_ERR(device);
-		goto del;
-	}
-
 	return 0;
-del:
-	cdev_del(&hidg->cdev);
 fail_free_descs:
 	usb_free_all_descriptors(f);
 fail:
@@ -1244,9 +1240,7 @@  static void hidg_free(struct usb_function *f)
 
 	hidg = func_to_hidg(f);
 	opts = container_of(f->fi, struct f_hid_opts, func_inst);
-	kfree(hidg->report_desc);
-	kfree(hidg->set_report_buf);
-	kfree(hidg);
+	put_device(&hidg->dev);
 	mutex_lock(&opts->lock);
 	--opts->refcnt;
 	mutex_unlock(&opts->lock);
@@ -1256,8 +1250,7 @@  static void hidg_unbind(struct usb_configuration *c, struct usb_function *f)
 {
 	struct f_hidg *hidg = func_to_hidg(f);
 
-	device_destroy(hidg_class, MKDEV(major, hidg->minor));
-	cdev_del(&hidg->cdev);
+	cdev_device_del(&hidg->cdev, &hidg->dev);
 
 	usb_free_all_descriptors(f);
 }
@@ -1266,6 +1259,7 @@  static struct usb_function *hidg_alloc(struct usb_function_instance *fi)
 {
 	struct f_hidg *hidg;
 	struct f_hid_opts *opts;
+	int ret;
 
 	/* allocate and initialize one new instance */
 	hidg = kzalloc(sizeof(*hidg), GFP_KERNEL);
@@ -1277,17 +1271,27 @@  static struct usb_function *hidg_alloc(struct usb_function_instance *fi)
 	mutex_lock(&opts->lock);
 	++opts->refcnt;
 
-	hidg->minor = opts->minor;
+	device_initialize(&hidg->dev);
+	hidg->dev.release = hidg_release;
+	hidg->dev.class = hidg_class;
+	hidg->dev.devt = MKDEV(major, opts->minor);
+	ret = dev_set_name(&hidg->dev, "hidg%d", opts->minor);
+	if (ret) {
+		--opts->refcnt;
+		mutex_unlock(&opts->lock);
+		return ERR_PTR(ret);
+	}
+
 	hidg->bInterfaceSubClass = opts->subclass;
 	hidg->bInterfaceProtocol = opts->protocol;
 	hidg->report_length = opts->report_length;
 	hidg->report_desc_length = opts->report_desc_length;
 	if (opts->report_desc) {
-		hidg->report_desc = kmemdup(opts->report_desc,
-					    opts->report_desc_length,
-					    GFP_KERNEL);
+		hidg->report_desc = devm_kmemdup(&hidg->dev, opts->report_desc,
+						 opts->report_desc_length,
+						 GFP_KERNEL);
 		if (!hidg->report_desc) {
-			kfree(hidg);
+			put_device(&hidg->dev);
 			mutex_unlock(&opts->lock);
 			return ERR_PTR(-ENOMEM);
 		}