[PATCH 3.16 36/87] usbip: usbip_host: fix stub_dev lock context imbalance regression

[Ben Hutchings]

3.16.75-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>

commit 3ea3091f1bd8586125848c62be295910e9802af0 upstream.

Fix the following sparse context imbalance regression introduced in
a patch that fixed sleeping function called from invalid context bug.

kbuild test robot reported on:

tree/branch: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git  usb-linus

Regressions in current branch:

drivers/usb/usbip/stub_dev.c:399:9: sparse: sparse: context imbalance in 'stub_probe' - different lock contexts for basic block
drivers/usb/usbip/stub_dev.c:418:13: sparse: sparse: context imbalance in 'stub_disconnect' - different lock contexts for basic block
drivers/usb/usbip/stub_dev.c:464:1-10: second lock on line 476

Error ids grouped by kconfigs:

recent_errors
âââ i386-allmodconfig
â   âââ drivers-usb-usbip-stub_dev.c:second-lock-on-line
âââ x86_64-allmodconfig
â   âââ drivers-usb-usbip-stub_dev.c:sparse:sparse:context-imbalance-in-stub_disconnect-different-lock-contexts-for-basic-block
â   âââ drivers-usb-usbip-stub_dev.c:sparse:sparse:context-imbalance-in-stub_probe-different-lock-contexts-for-basic-block
âââ x86_64-allyesconfig
    âââ drivers-usb-usbip-stub_dev.c:second-lock-on-line

This is a real problem in an error leg where spin_lock() is called on an
already held lock.

Fix the imbalance in stub_probe() and stub_disconnect().

Signed-off-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
Fixes: 0c9e8b3cad65 ("usbip: usbip_host: fix BUG: sleeping function called from invalid context")
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/staging/usbip/stub_dev.c | 36 +++++++++++++++++++++++-------------
 1 file changed, 23 insertions(+), 13 deletions(-)

--- a/drivers/staging/usbip/stub_dev.c
+++ b/drivers/staging/usbip/stub_dev.c
@@ -367,14 +367,17 @@ static int stub_probe(struct usb_device
 		 * See driver_probe_device() in driver/base/dd.c
 		 */
 		rc = -ENODEV;
-		goto sdev_free;
+		if (!busid_priv)
+			goto sdev_free;
+
+		goto call_put_busid_priv;
 	}
 
 	if (udev->descriptor.bDeviceClass == USB_CLASS_HUB) {
 		dev_dbg(&udev->dev, "%s is a usb hub device... skip!\n",
 			 udev_busid);
 		rc = -ENODEV;
-		goto sdev_free;
+		goto call_put_busid_priv;
 	}
 
 	if (!strcmp(udev->bus->bus_name, "vhci_hcd")) {
@@ -383,7 +386,7 @@ static int stub_probe(struct usb_device
 			udev_busid);
 
 		rc = -ENODEV;
-		goto sdev_free;
+		goto call_put_busid_priv;
 	}
 
 
@@ -402,6 +405,9 @@ static int stub_probe(struct usb_device
 	save_status = busid_priv->status;
 	busid_priv->status = STUB_BUSID_ALLOC;
 
+	/* release the busid_lock */
+	put_busid_priv(busid_priv);
+
 	/*
 	 * Claim this hub port.
 	 * It doesn't matter what value we pass as owner
@@ -414,9 +420,6 @@ static int stub_probe(struct usb_device
 		goto err_port;
 	}
 
-	/* release the busid_lock */
-	put_busid_priv(busid_priv);
-
 	rc = stub_add_files(&udev->dev);
 	if (rc) {
 		dev_err(&udev->dev, "stub_add_files for %s\n", udev_busid);
@@ -437,11 +440,17 @@ err_port:
 	spin_lock(&busid_priv->busid_lock);
 	busid_priv->sdev = NULL;
 	busid_priv->status = save_status;
-sdev_free:
-	stub_device_free(sdev);
+	spin_unlock(&busid_priv->busid_lock);
+	/* lock is released - go to free */
+	goto sdev_free;
+
+call_put_busid_priv:
 	/* release the busid_lock */
 	put_busid_priv(busid_priv);
 
+sdev_free:
+	stub_device_free(sdev);
+
 	return rc;
 }
 
@@ -477,7 +486,9 @@ static void stub_disconnect(struct usb_d
 	/* get stub_device */
 	if (!sdev) {
 		dev_err(&udev->dev, "could not get device");
-		goto call_put_busid_priv;
+		/* release busid_lock */
+		put_busid_priv(busid_priv);
+		return;
 	}
 
 	dev_set_drvdata(&udev->dev, NULL);
@@ -507,7 +518,7 @@ static void stub_disconnect(struct usb_d
 	if (!busid_priv->shutdown_busid)
 		busid_priv->shutdown_busid = 1;
 	/* release busid_lock */
-	put_busid_priv(busid_priv);
+	spin_unlock(&busid_priv->busid_lock);
 
 	/* shutdown the current connection */
 	shutdown_busid(busid_priv);
@@ -522,10 +533,9 @@ static void stub_disconnect(struct usb_d
 
 	if (busid_priv->status == STUB_BUSID_ALLOC)
 		busid_priv->status = STUB_BUSID_ADDED;
-
-call_put_busid_priv:
 	/* release busid_lock */
-	put_busid_priv(busid_priv);
+	spin_unlock(&busid_priv->busid_lock);
+	return;
 }
 
 #ifdef CONFIG_PM