From: Johan Hovold <jo...@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 <sta...@vger.kernel.org> # 2.6.24
Reported-by: syzbot+f9549f5ee8a5416f0...@syzkaller.appspotmail.com
Tested-by: syzbot+f9549f5ee8a5416f0...@syzkaller.appspotmail.com
Signed-off-by: Johan Hovold <jo...@kernel.org>
Link: https://lore.kernel.org/r/20190919083039.30898-3-jo...@kernel.org
Signed-off-by: Greg Kroah-Hartman <gre...@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
@@ -183,7 +183,6 @@ 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
@@ -336,18 +335,14 @@ 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;
}
@@ -355,12 +350,10 @@ 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,
@@ -427,10 +420,9 @@ 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;
@@ -460,10 +452,7 @@ static int tower_release (struct inode *
unlock_exit:
mutex_unlock(&dev->lock);
-
exit:
- mutex_unlock(&open_disc_mutex);
-exit_nolock:
return retval;
}
@@ -915,7 +904,6 @@ 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;
@@ -947,16 +935,13 @@ 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) {
