Re: [PATCH] usbip: vudc: fix null pointer dereference on udc->lock

From: Krzysztof Opasiak
Date: Tue Feb 27 2018 - 08:24:57 EST




On 02/26/2018 05:40 PM, Shuah Khan wrote:
On 02/22/2018 10:39 AM, Colin King wrote:
From: Colin Ian King <colin.king@xxxxxxxxxxxxx>

Currently the driver attempts to spin lock on udc->lock before a NULL
pointer check is performed on udc, hence there is a potential null
pointer dereference on udc->lock. Fix this by moving the null check
on udc before the lock occurs.

Fixes: ea6873a45a22 ("usbip: vudc: Add SysFS infrastructure for VUDC")
Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
---
drivers/usb/usbip/vudc_sysfs.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/usbip/vudc_sysfs.c b/drivers/usb/usbip/vudc_sysfs.c
index d86f72bbbb91..6dcd3ff655c3 100644
--- a/drivers/usb/usbip/vudc_sysfs.c
+++ b/drivers/usb/usbip/vudc_sysfs.c
@@ -105,10 +105,14 @@ static ssize_t usbip_sockfd_store(struct device *dev, struct device_attribute *a
if (rv != 0)
return -EINVAL;
+ if (!udc) {
+ dev_err(dev, "no device");
+ return -ENODEV;
+ }
spin_lock_irqsave(&udc->lock, flags);
/* Don't export what we don't have */
- if (!udc || !udc->driver || !udc->pullup) {
- dev_err(dev, "no device or gadget not bound");
+ if (!udc->driver || !udc->pullup) {
+ dev_err(dev, "gadget not bound");
ret = -ENODEV;
goto unlock;
}


Thanks for the patch. Looks good to me.

Acked-by: Shuah Khan <shuahkh@xxxxxxxxxxxxxxx>

Reviewed-by: Krzysztof Opasiak <k.opasiak@xxxxxxxxxxx>

but you could fix also a similar bug one one function above (dev_desc_read()) ;)

Best regards,
--
Krzysztof Opasiak
Samsung R&D Institute Poland
Samsung Electronics