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From:   Colin King <colin.king@canonical.com>
To:     Shuah Khan <shuah@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-usb@vger.kernel.org
Cc:     kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] usbip: vudc: fix null pointer dereference on udc->lock
Date:   Thu, 22 Feb 2018 17:39:17 +0000
Message-Id: <20180222173917.10841-1-colin.king@canonical.com>
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Sender: linux-kernel-owner@vger.kernel.org
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From: Colin Ian King <colin.king@canonical.com>

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@canonical.com>
---
 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;
 	}
-- 
2.15.1