[PATCH][V2] usb: isp1760: fix null dereference if kzalloc returns null

[PATCH][V2] usb: isp1760: fix null dereference if kzalloc returns null

[Colin King]

From: Colin Ian King <colin.king@canonical.com>

If kzalloc returns null then isp1760_ep_alloc_request performs
a null pointer dereference on req. Check for null to avoid this.

Detected with smatch static analysis:

drivers/usb/isp1760/isp1760-udc.c:816 isp1760_ep_alloc_request()
  error: potential null dereference 'req'.  (kzalloc returns null)

Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/usb/isp1760/isp1760-udc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/usb/isp1760/isp1760-udc.c b/drivers/usb/isp1760/isp1760-udc.c
index 3fc4fe7..18ebf5b 100644
--- a/drivers/usb/isp1760/isp1760-udc.c
+++ b/drivers/usb/isp1760/isp1760-udc.c
@@ -812,6 +812,8 @@ static struct usb_request *isp1760_ep_alloc_request(struct usb_ep *ep,
 	struct isp1760_request *req;
 
 	req = kzalloc(sizeof(*req), gfp_flags);
+	if (!req)
+		return NULL;
 
 	return &req->req;
 }
-- 
2.1.4

Re: [PATCH][V2] usb: isp1760: fix null dereference if kzalloc returns null

[Sergei Shtylyov]

Hello.

On 6/1/2015 1:43 AM, Colin King wrote:

> From: Colin Ian King <colin.king@canonical.com>

> If kzalloc returns null then isp1760_ep_alloc_request performs
> a null pointer dereference on req. Check for null to avoid this.

    I told you there's no dereference and yet you're repeating it again. :-(

> Detected with smatch static analysis:

> drivers/usb/isp1760/isp1760-udc.c:816 isp1760_ep_alloc_request()
>    error: potential null dereference 'req'.  (kzalloc returns null)

> Signed-off-by: Colin Ian King <colin.king@canonical.com>

WBR, Sergei

Re: [PATCH][V2] usb: isp1760: fix null dereference if kzalloc returns null

[Laurent Pinchart]

On Monday 01 June 2015 16:51:30 Sergei Shtylyov wrote:
> Hello.
> 
> On 6/1/2015 1:43 AM, Colin King wrote:
> > From: Colin Ian King <colin.king@canonical.com>
> > 
> > If kzalloc returns null then isp1760_ep_alloc_request performs
> > a null pointer dereference on req. Check for null to avoid this.
> 
> I told you there's no dereference and yet you're repeating it again. :-(

How about

"isp1760_ep_alloc_request allocates a structure with kzalloc without checking 
for NULL and then returns a pointer to one of the structure fields. As the 
field happens to be the first in the structure the caller can properly check 
for NULL, but this is risky if the structure layout is changed later. Add an 
explicit NULL check for the kzalloc return value."

> > a null pointer dereference on req. Check for null to avoid this.
> >
> > Detected with smatch static analysis:
> > 
> > drivers/usb/isp1760/isp1760-udc.c:816 isp1760_ep_alloc_request()
> > 
> >    error: potential null dereference 'req'.  (kzalloc returns null)
> > 
> > Signed-off-by: Colin Ian King <colin.king@canonical.com>

-- 
Regards,

Laurent Pinchart

Re: [PATCH][V2] usb: isp1760: fix null dereference if kzalloc returns null

[Sergei Shtylyov]

Hello.

On 06/02/2015 06:41 PM, Laurent Pinchart wrote:

>>> From: Colin Ian King <colin.king@canonical.com>

>>> If kzalloc returns null then isp1760_ep_alloc_request performs
>>> a null pointer dereference on req. Check for null to avoid this.

>> I told you there's no dereference and yet you're repeating it again. :-(

> How about

> "isp1760_ep_alloc_request allocates a structure with kzalloc without checking
> for NULL and then returns a pointer to one of the structure fields. As the
> field happens to be the first in the structure the caller can properly check
> for NULL, but this is risky if the structure layout is changed later. Add an
> explicit NULL check for the kzalloc return value."

    Fine with me! Thanks, Laurent. :-)

>>> a null pointer dereference on req. Check for null to avoid this.

>>> Detected with smatch static analysis:

>>> drivers/usb/isp1760/isp1760-udc.c:816 isp1760_ep_alloc_request()

>>>     error: potential null dereference 'req'.  (kzalloc returns null)

>>> Signed-off-by: Colin Ian King <colin.king@canonical.com>

WBR, Sergei