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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@kernel.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@kernel.org>
Link: https://lore.kernel.org/r/20191009153848.8664-4-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.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);
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