USB: ldusb: fix NULL-derefs on driver unbind

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")
Cc: stable <stable@vger.kernel.org>     # 2.6.13
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20191009153848.8664-4-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/misc/ldusb.c b/drivers/usb/misc/ldusb.c
index 6581774bdfa4929611ba605d693970229eba3efb..f3108d85e768086293954e8a869b79d4a75901e2 100644 (file)
--- a/drivers/usb/misc/ldusb.c
+++ b/drivers/usb/misc/ldusb.c
@@ -153,6 +153,7 @@ MODULE_PARM_DESC(min_interrupt_out_interval, "Minimum interrupt out interval in
 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 */
 
@@ -192,12 +193,10 @@ static void ld_usb_abort_transfers(struct ld_usb *dev)
        /* 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);
 }
 
 /**
@@ -205,8 +204,6 @@ static void ld_usb_abort_transfers(struct ld_usb *dev)
  */
 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);
@@ -263,7 +260,7 @@ static void ld_usb_interrupt_in_callback(struct urb *urb)
 
 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,
@@ -392,7 +389,7 @@ static int ld_usb_release(struct inode *inode, struct file *file)
                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 */
@@ -423,7 +420,7 @@ static __poll_t ld_usb_poll(struct file *file, poll_table *wait)
 
        dev = file->private_data;
 
-       if (!dev->intf)
+       if (dev->disconnected)
                return EPOLLERR | EPOLLHUP;
 
        poll_wait(file, &dev->read_wait, wait);
@@ -462,7 +459,7 @@ static ssize_t ld_usb_read(struct file *file, char __user *buffer, size_t count,
        }
 
        /* 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;
@@ -542,7 +539,7 @@ static ssize_t ld_usb_write(struct file *file, const char __user *buffer,
        }
 
        /* 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;
@@ -764,6 +761,9 @@ static void ld_usb_disconnect(struct usb_interface *intf)
        /* 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 */
@@ -771,7 +771,7 @@ static void ld_usb_disconnect(struct usb_interface *intf)
                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);