[PATCH 0/4] USB: legousbtower: misc fixes

[PATCH 0/4] USB: legousbtower: misc fixes

[Johan Hovold]

This series fixes a few issues found in the legousbtower driver. The
potential deadlock issue was reported by syzbot, and the rest was found
through inspection.

I have bunch of clean ups for this driver as well that I'll post once
these are in Linus's tree.

Johan


Johan Hovold (4):
  USB: legousbtower: fix slab info leak at probe
  USB: legousbtower: fix deadlock on disconnect
  USB: legousbtower: fix potential NULL-deref on disconnect
  USB: legousbtower: fix open after failed reset request

 drivers/usb/misc/legousbtower.c | 55 ++++++++++++++-------------------
 1 file changed, 23 insertions(+), 32 deletions(-)

-- 
2.23.0

[PATCH 1/4] USB: legousbtower: fix slab info leak at probe

[Johan Hovold]

Make sure to check for short transfers when retrieving the version
information at probe to avoid leaking uninitialised slab data when
logging it.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/misc/legousbtower.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/misc/legousbtower.c b/drivers/usb/misc/legousbtower.c
index 006cf13b2199..1db07d4dc738 100644
--- a/drivers/usb/misc/legousbtower.c
+++ b/drivers/usb/misc/legousbtower.c
@@ -891,8 +891,10 @@ static int tower_probe (struct usb_interface *interface, const struct usb_device
 				  get_version_reply,
 				  sizeof(*get_version_reply),
 				  1000);
-	if (result < 0) {
-		dev_err(idev, "LEGO USB Tower get version control request failed\n");
+	if (result < sizeof(*get_version_reply)) {
+		if (result >= 0)
+			result = -EIO;
+		dev_err(idev, "get version request failed: %d\n", result);
 		retval = result;
 		goto error;
 	}
-- 
2.23.0

[PATCH 2/4] USB: legousbtower: fix deadlock on disconnect

[Johan Hovold]

Fix a potential deadlock if disconnect races with open.

Since commit d4ead16f50f9 ("USB: prevent char device open/deregister
race") core holds an rw-semaphore while open is called and when
releasing the minor number during deregistration. This can lead to an
ABBA deadlock if a driver takes a lock in open which it also holds
during deregistration.

This effectively reverts commit 78663ecc344b ("USB: disconnect open race
in legousbtower") which needlessly introduced this issue after a generic
fix for this race had been added to core by commit d4ead16f50f9 ("USB:
prevent char device open/deregister race").

Fixes: 78663ecc344b ("USB: disconnect open race in legousbtower")
Cc: stable <stable@vger.kernel.org>	# 2.6.24
Reported-by: syzbot+f9549f5ee8a5416f0b95@syzkaller.appspotmail.com
Tested-by: syzbot+f9549f5ee8a5416f0b95@syzkaller.appspotmail.com
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/misc/legousbtower.c | 19 ++-----------------
 1 file changed, 2 insertions(+), 17 deletions(-)

diff --git a/drivers/usb/misc/legousbtower.c b/drivers/usb/misc/legousbtower.c
index 1db07d4dc738..773e4188f336 100644
--- a/drivers/usb/misc/legousbtower.c
+++ b/drivers/usb/misc/legousbtower.c
@@ -179,7 +179,6 @@ static const struct usb_device_id tower_table[] = {
 };
 
 MODULE_DEVICE_TABLE (usb, tower_table);
-static DEFINE_MUTEX(open_disc_mutex);
 
 #define LEGO_USB_TOWER_MINOR_BASE	160
 
@@ -332,18 +331,14 @@ static int tower_open (struct inode *inode, struct file *file)
 		goto exit;
 	}
 
-	mutex_lock(&open_disc_mutex);
 	dev = usb_get_intfdata(interface);
-
 	if (!dev) {
-		mutex_unlock(&open_disc_mutex);
 		retval = -ENODEV;
 		goto exit;
 	}
 
 	/* lock this device */
 	if (mutex_lock_interruptible(&dev->lock)) {
-		mutex_unlock(&open_disc_mutex);
 	        retval = -ERESTARTSYS;
 		goto exit;
 	}
@@ -351,12 +346,10 @@ static int tower_open (struct inode *inode, struct file *file)
 
 	/* allow opening only once */
 	if (dev->open_count) {
-		mutex_unlock(&open_disc_mutex);
 		retval = -EBUSY;
 		goto unlock_exit;
 	}
 	dev->open_count = 1;
-	mutex_unlock(&open_disc_mutex);
 
 	/* reset the tower */
 	result = usb_control_msg (dev->udev,
@@ -423,10 +416,9 @@ static int tower_release (struct inode *inode, struct file *file)
 
 	if (dev == NULL) {
 		retval = -ENODEV;
-		goto exit_nolock;
+		goto exit;
 	}
 
-	mutex_lock(&open_disc_mutex);
 	if (mutex_lock_interruptible(&dev->lock)) {
 	        retval = -ERESTARTSYS;
 		goto exit;
@@ -456,10 +448,7 @@ static int tower_release (struct inode *inode, struct file *file)
 
 unlock_exit:
 	mutex_unlock(&dev->lock);
-
 exit:
-	mutex_unlock(&open_disc_mutex);
-exit_nolock:
 	return retval;
 }
 
@@ -912,7 +901,6 @@ static int tower_probe (struct usb_interface *interface, const struct usb_device
 	if (retval) {
 		/* something prevented us from registering this driver */
 		dev_err(idev, "Not able to get a minor for this device.\n");
-		usb_set_intfdata (interface, NULL);
 		goto error;
 	}
 	dev->minor = interface->minor;
@@ -944,16 +932,13 @@ static void tower_disconnect (struct usb_interface *interface)
 	int minor;
 
 	dev = usb_get_intfdata (interface);
-	mutex_lock(&open_disc_mutex);
-	usb_set_intfdata (interface, NULL);
 
 	minor = dev->minor;
 
-	/* give back our minor */
+	/* give back our minor and prevent further open() */
 	usb_deregister_dev (interface, &tower_class);
 
 	mutex_lock(&dev->lock);
-	mutex_unlock(&open_disc_mutex);
 
 	/* if the device is not opened, then we clean up right now */
 	if (!dev->open_count) {
-- 
2.23.0

[PATCH 3/4] USB: legousbtower: fix potential NULL-deref on disconnect

[Johan Hovold]

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>
---
 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);
-- 
2.23.0

[PATCH 4/4] USB: legousbtower: fix open after failed reset request

[Johan Hovold]

The driver would return with a nonzero open count in case the reset
control request failed. This would prevent any further attempts to open
the char dev until the device was disconnected.

Fix this by incrementing the open count only on successful open.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/misc/legousbtower.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/misc/legousbtower.c b/drivers/usb/misc/legousbtower.c
index 4fa999882635..44d6a3381804 100644
--- a/drivers/usb/misc/legousbtower.c
+++ b/drivers/usb/misc/legousbtower.c
@@ -348,7 +348,6 @@ static int tower_open (struct inode *inode, struct file *file)
 		retval = -EBUSY;
 		goto unlock_exit;
 	}
-	dev->open_count = 1;
 
 	/* reset the tower */
 	result = usb_control_msg (dev->udev,
@@ -388,13 +387,14 @@ static int tower_open (struct inode *inode, struct file *file)
 		dev_err(&dev->udev->dev,
 			"Couldn't submit interrupt_in_urb %d\n", retval);
 		dev->interrupt_in_running = 0;
-		dev->open_count = 0;
 		goto unlock_exit;
 	}
 
 	/* save device in the file's private structure */
 	file->private_data = dev;
 
+	dev->open_count = 1;
+
 unlock_exit:
 	mutex_unlock(&dev->lock);
 
-- 
2.23.0