linux-kernel - [PATCH 3.16 054/136] USB: ldusb: fix NULL-derefs on driver unbind

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Date:   Tue, 17 Dec 2019 00:46:28 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Johan Hovold" <johan@...nel.org>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
Subject: [PATCH 3.16 054/136] USB: ldusb: fix NULL-derefs on driver unbind

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

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

From: Johan Hovold <johan@...nel.org>

commit 58ecf131e74620305175a7aa103f81350bb37570 upstream.

The driver was using its struct usb_interface pointer as an inverted
disconnected flag, but was setting it to NULL before making sure all
completion handlers had run. This could lead to a NULL-pointer
dereference in a number of dev_dbg, dev_warn and dev_err statements in
the completion handlers which relies on said pointer.

Fix this by unconditionally stopping all I/O and preventing
resubmissions by poisoning the interrupt URBs at disconnect and using a
dedicated disconnected flag.

This also makes sure that all I/O has completed by the time the
disconnect callback returns.

Fixes: 2824bd250f0b ("[PATCH] USB: add ldusb driver")
Signed-off-by: Johan Hovold <johan@...nel.org>
Link: https://lore.kernel.org/r/20191009153848.8664-4-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/usb/misc/ldusb.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

--- a/drivers/usb/misc/ldusb.c
+++ b/drivers/usb/misc/ldusb.c
@@ -168,6 +168,7 @@ MODULE_PARM_DESC(min_interrupt_out_inter
 struct ld_usb {
 	struct mutex		mutex;		/* locks this structure */
 	struct usb_interface*	intf;		/* save off the usb interface pointer */
+	unsigned long		disconnected:1;
 
 	int			open_count;	/* number of times this port has been opened */
 
@@ -207,12 +208,10 @@ static void ld_usb_abort_transfers(struc
 	/* shutdown transfer */
 	if (dev->interrupt_in_running) {
 		dev->interrupt_in_running = 0;
-		if (dev->intf)
-			usb_kill_urb(dev->interrupt_in_urb);
+		usb_kill_urb(dev->interrupt_in_urb);
 	}
 	if (dev->interrupt_out_busy)
-		if (dev->intf)
-			usb_kill_urb(dev->interrupt_out_urb);
+		usb_kill_urb(dev->interrupt_out_urb);
 }
 
 /**
@@ -220,8 +219,6 @@ static void ld_usb_abort_transfers(struc
  */
 static void ld_usb_delete(struct ld_usb *dev)
 {
-	ld_usb_abort_transfers(dev);
-
 	/* free data structures */
 	usb_free_urb(dev->interrupt_in_urb);
 	usb_free_urb(dev->interrupt_out_urb);
@@ -277,7 +274,7 @@ static void ld_usb_interrupt_in_callback
 
 resubmit:
 	/* resubmit if we're still running */
-	if (dev->interrupt_in_running && !dev->buffer_overflow && dev->intf) {
+	if (dev->interrupt_in_running && !dev->buffer_overflow) {
 		retval = usb_submit_urb(dev->interrupt_in_urb, GFP_ATOMIC);
 		if (retval) {
 			dev_err(&dev->intf->dev,
@@ -406,7 +403,7 @@ static int ld_usb_release(struct inode *
 		retval = -ENODEV;
 		goto unlock_exit;
 	}
-	if (dev->intf == NULL) {
+	if (dev->disconnected) {
 		/* the device was unplugged before the file was released */
 		mutex_unlock(&dev->mutex);
 		/* unlock here as ld_usb_delete frees dev */
@@ -437,7 +434,7 @@ static unsigned int ld_usb_poll(struct f
 
 	dev = file->private_data;
 
-	if (!dev->intf)
+	if (dev->disconnected)
 		return POLLERR | POLLHUP;
 
 	poll_wait(file, &dev->read_wait, wait);
@@ -476,7 +473,7 @@ static ssize_t ld_usb_read(struct file *
 	}
 
 	/* verify that the device wasn't unplugged */
-	if (dev->intf == NULL) {
+	if (dev->disconnected) {
 		retval = -ENODEV;
 		printk(KERN_ERR "ldusb: No device or device unplugged %d\n", retval);
 		goto unlock_exit;
@@ -556,7 +553,7 @@ static ssize_t ld_usb_write(struct file
 	}
 
 	/* verify that the device wasn't unplugged */
-	if (dev->intf == NULL) {
+	if (dev->disconnected) {
 		retval = -ENODEV;
 		printk(KERN_ERR "ldusb: No device or device unplugged %d\n", retval);
 		goto unlock_exit;
@@ -792,6 +789,9 @@ static void ld_usb_disconnect(struct usb
 	/* give back our minor */
 	usb_deregister_dev(intf, &ld_usb_class);
 
+	usb_poison_urb(dev->interrupt_in_urb);
+	usb_poison_urb(dev->interrupt_out_urb);
+
 	mutex_lock(&dev->mutex);
 
 	/* if the device is not opened, then we clean up right now */
@@ -799,7 +799,7 @@ static void ld_usb_disconnect(struct usb
 		mutex_unlock(&dev->mutex);
 		ld_usb_delete(dev);
 	} else {
-		dev->intf = NULL;
+		dev->disconnected = 1;
 		/* wake up pollers */
 		wake_up_interruptible_all(&dev->read_wait);
 		wake_up_interruptible_all(&dev->write_wait);