This is a note to let you know that I've just added the patch titled

USB: legousbtower: fix potential NULL-deref on disconnect

to my usb git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From cd81e6fa8e033e7bcd59415b4a65672b4780030b Mon Sep 17 00:00:00 2001

From: Johan Hovold johan@kernel.org Date: Thu, 19 Sep 2019 10:30:38 +0200 Subject: USB: legousbtower: fix potential NULL-deref on disconnect

The driver is using its struct usb_device 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 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: 9d974b2a06e3 ("USB: legousbtower.c: remove err() usage") Fixes: fef526cae700 ("USB: legousbtower: remove custom debug macro") Fixes: 4dae99638097 ("USB: legotower: remove custom debug macro and module parameter") Cc: stable stable@vger.kernel.org # 3.5 Signed-off-by: Johan Hovold johan@kernel.org Link: https://lore.kernel.org/r/20190919083039.30898-4-johan@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/misc/legousbtower.c | 26 +++++++++++++++----------- 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/drivers/usb/misc/legousbtower.c b/drivers/usb/misc/legousbtower.c index 773e4188f336..4fa999882635 100644 --- a/drivers/usb/misc/legousbtower.c +++ b/drivers/usb/misc/legousbtower.c @@ -190,6 +190,7 @@ struct lego_usb_tower { unsigned char minor; /* the starting minor number for this device */

int open_count; /* number of times this port has been opened */ + unsigned long disconnected:1;

char* read_buffer; size_t read_buffer_length; /* this much came in */ @@ -289,8 +290,6 @@ static inline void lego_usb_tower_debug_data(struct device *dev, */ static inline void tower_delete (struct lego_usb_tower *dev) { - tower_abort_transfers (dev); - /* free data structures */ usb_free_urb(dev->interrupt_in_urb); usb_free_urb(dev->interrupt_out_urb); @@ -430,7 +429,8 @@ static int tower_release (struct inode *inode, struct file *file) retval = -ENODEV; goto unlock_exit; } - if (dev->udev == NULL) { + + if (dev->disconnected) { /* the device was unplugged before the file was released */

/* unlock here as tower_delete frees dev */ @@ -466,10 +466,9 @@ static void tower_abort_transfers (struct lego_usb_tower *dev) if (dev->interrupt_in_running) { dev->interrupt_in_running = 0; mb(); - if (dev->udev) - usb_kill_urb (dev->interrupt_in_urb); + usb_kill_urb(dev->interrupt_in_urb); } - if (dev->interrupt_out_busy && dev->udev) + if (dev->interrupt_out_busy) usb_kill_urb(dev->interrupt_out_urb); }

@@ -505,7 +504,7 @@ static __poll_t tower_poll (struct file *file, poll_table *wait)

dev = file->private_data;

- if (!dev->udev) + if (dev->disconnected) return EPOLLERR | EPOLLHUP;

poll_wait(file, &dev->read_wait, wait); @@ -552,7 +551,7 @@ static ssize_t tower_read (struct file *file, char __user *buffer, size_t count, }

/* verify that the device wasn't unplugged */ - if (dev->udev == NULL) { + if (dev->disconnected) { retval = -ENODEV; pr_err("No device or device unplugged %d\n", retval); goto unlock_exit; @@ -638,7 +637,7 @@ static ssize_t tower_write (struct file *file, const char __user *buffer, size_t }

/* verify that the device wasn't unplugged */ - if (dev->udev == NULL) { + if (dev->disconnected) { retval = -ENODEV; pr_err("No device or device unplugged %d\n", retval); goto unlock_exit; @@ -748,7 +747,7 @@ static void tower_interrupt_in_callback (struct urb *urb)

resubmit: /* resubmit if we're still running */ - if (dev->interrupt_in_running && dev->udev) { + if (dev->interrupt_in_running) { retval = usb_submit_urb (dev->interrupt_in_urb, GFP_ATOMIC); if (retval) dev_err(&dev->udev->dev, @@ -813,6 +812,7 @@ static int tower_probe (struct usb_interface *interface, const struct usb_device

dev->udev = udev; dev->open_count = 0; + dev->disconnected = 0;

dev->read_buffer = NULL; dev->read_buffer_length = 0; @@ -938,6 +938,10 @@ static void tower_disconnect (struct usb_interface *interface) /* give back our minor and prevent further open() */ usb_deregister_dev (interface, &tower_class);

+ /* stop I/O */ + usb_poison_urb(dev->interrupt_in_urb); + usb_poison_urb(dev->interrupt_out_urb); + mutex_lock(&dev->lock);

/* if the device is not opened, then we clean up right now */ @@ -945,7 +949,7 @@ static void tower_disconnect (struct usb_interface *interface) mutex_unlock(&dev->lock); tower_delete (dev); } else { - dev->udev = NULL; + dev->disconnected = 1; /* wake up pollers */ wake_up_interruptible_all(&dev->read_wait); wake_up_interruptible_all(&dev->write_wait);