[PATCH][hid] Fix a NULL pointer dereference when we fail to allocate memory

Hi,

If, in usb_hid_configure(), we fail to allocate storage for 'usbhid', 
 "if (!(usbhid = kzalloc(sizeof(struct usbhid_device), GFP_KERNEL)))", 
then we'll jump to the 'fail:' label where we have this code:
        usb_free_urb(usbhid->urbin);
        usb_free_urb(usbhid->urbout);
        usb_free_urb(usbhid->urbctrl);
Since we got here because we couldn't allocate storage for 'usbhid', 
what we have here is a NULL pointer dereference - ouch...

This patch solves that little problem by adding a new 
'fail_no_usbhid:' label after the problematic calls to 
usb_free_urb() and jumps to that one instead, in the problem case.


Signed-off-by: Jesper Juhl <redacted>
---

 drivers/hid/usbhid/hid-core.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/hid/usbhid/hid-core.c b/drivers/hid/usbhid/hid-core.c
index b2baeae..3ff7468 100644
--- a/drivers/hid/usbhid/hid-core.c
+++ b/drivers/hid/usbhid/hid-core.c

@@ -743,7 +743,7 @@ static struct hid_device *usb_hid_configure(struct usb_interface *intf)
 	hid->quirks = quirks;
 
 	if (!(usbhid = kzalloc(sizeof(struct usbhid_device), GFP_KERNEL)))
-		goto fail;
+		goto fail_no_usbhid;
 
 	hid->driver_data = usbhid;
 	usbhid->hid = hid;

@@ -877,6 +877,7 @@ fail:
 	usb_free_urb(usbhid->urbin);
 	usb_free_urb(usbhid->urbout);
 	usb_free_urb(usbhid->urbctrl);
+fail_no_usbhid:
 	hid_free_buffers(dev, hid);
 	hid_free_device(hid);
 

Jesper Juhl napsal(a):

Out of curiosity, where is this freed?

-- 
Jiri Slaby (jirislaby@gmail.com)
Faculty of Informatics, Masaryk University

On Sun, 22 Jul 2007, Jiri Slaby wrote:

quoted

--- a/drivers/hid/usbhid/hid-core.c
+++ b/drivers/hid/usbhid/hid-core.c

@@ -743,7 +743,7 @@ static struct hid_device *usb_hid_configure(struct usb_interface *intf)
 	hid->quirks = quirks;
 
 	if (!(usbhid = kzalloc(sizeof(struct usbhid_device), GFP_KERNEL)))

Out of curiosity, where is this freed?

I have queued the fix below on top of Jesper's patch, thanks.

diff --git a/drivers/hid/usbhid/hid-core.c b/drivers/hid/usbhid/hid-core.c
index 3ff7468..6e73934 100644
--- a/drivers/hid/usbhid/hid-core.c
+++ b/drivers/hid/usbhid/hid-core.c

@@ -877,6 +877,7 @@ fail:
 	usb_free_urb(usbhid->urbin);
 	usb_free_urb(usbhid->urbout);
 	usb_free_urb(usbhid->urbctrl);
+	kfree(usbhid);
 fail_no_usbhid:
 	hid_free_buffers(dev, hid);
 	hid_free_device(hid);

@@ -912,6 +913,7 @@ static void hid_disconnect(struct usb_interface *intf)
 	usb_free_urb(usbhid->urbin);
 	usb_free_urb(usbhid->urbctrl);
 	usb_free_urb(usbhid->urbout);
+	kfree(usbhid);
 
 	hid_free_buffers(hid_to_usb_dev(hid), hid);
 	hid_free_device(hid);

On 22/07/07, Jiri Slaby [off-list ref] wrote:

Jesper Juhl napsal(a):

quoted

 drivers/hid/usbhid/hid-core.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/hid/usbhid/hid-core.c b/drivers/hid/usbhid/hid-core.c
index b2baeae..3ff7468 100644
--- a/drivers/hid/usbhid/hid-core.c
+++ b/drivers/hid/usbhid/hid-core.c

@@ -743,7 +743,7 @@ static struct hid_device *usb_hid_configure(struct usb_interface *intf)
      hid->quirks = quirks;

      if (!(usbhid = kzalloc(sizeof(struct usbhid_device), GFP_KERNEL)))

Out of curiosity, where is this freed?

Sorry, I didn't notice your email until now.  It's not freed anywhere
:-(   But I see that Jiri Kosina just queued a fix for that, so now
all is good :-)

-- 
Jesper Juhl [off-list ref]
Don't top-post  http://www.catb.org/~esr/jargon/html/T/top-post.html
Plain text mails only, please      http://www.expita.com/nomime.html

On Sun, 22 Jul 2007, Jesper Juhl wrote:

If, in usb_hid_configure(), we fail to allocate storage for 'usbhid', 
 "if (!(usbhid = kzalloc(sizeof(struct usbhid_device), GFP_KERNEL)))", 
then we'll jump to the 'fail:' label where we have this code:
        usb_free_urb(usbhid->urbin);
        usb_free_urb(usbhid->urbout);
        usb_free_urb(usbhid->urbctrl);
Since we got here because we couldn't allocate storage for 'usbhid', 
what we have here is a NULL pointer dereference - ouch...

Hi Jesper,

thanks a lot for noticing this, I have queued your patch in HID tree.

(and sorry for late reply, I was offline on vacation for some time).

-- 
Jiri Kosina