| From 33a7813219f208f4952ece60ee255fd983272dec Mon Sep 17 00:00:00 2001 |
| From: Johan Hovold <johan@kernel.org> |
| Date: Thu, 19 Sep 2019 10:30:37 +0200 |
| Subject: USB: legousbtower: fix deadlock on disconnect |
| |
| From: Johan Hovold <johan@kernel.org> |
| |
| commit 33a7813219f208f4952ece60ee255fd983272dec upstream. |
| |
| 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> |
| Link: https://lore.kernel.org/r/20190919083039.30898-3-johan@kernel.org |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/usb/misc/legousbtower.c | 19 ++----------------- |
| 1 file changed, 2 insertions(+), 17 deletions(-) |
| |
| --- a/drivers/usb/misc/legousbtower.c |
| +++ b/drivers/usb/misc/legousbtower.c |
| @@ -185,7 +185,6 @@ static const struct usb_device_id tower_ |
| }; |
| |
| MODULE_DEVICE_TABLE (usb, tower_table); |
| -static DEFINE_MUTEX(open_disc_mutex); |
| |
| #define LEGO_USB_TOWER_MINOR_BASE 160 |
| |
| @@ -338,18 +337,14 @@ static int tower_open (struct inode *ino |
| 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; |
| } |
| @@ -357,12 +352,10 @@ static int tower_open (struct inode *ino |
| |
| /* 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, |
| @@ -429,10 +422,9 @@ static int tower_release (struct inode * |
| |
| 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; |
| @@ -462,10 +454,7 @@ static int tower_release (struct inode * |
| |
| unlock_exit: |
| mutex_unlock(&dev->lock); |
| - |
| exit: |
| - mutex_unlock(&open_disc_mutex); |
| -exit_nolock: |
| return retval; |
| } |
| |
| @@ -932,7 +921,6 @@ static int tower_probe (struct usb_inter |
| 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; |
| @@ -964,16 +952,13 @@ static void tower_disconnect (struct usb |
| 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) { |