From: Johan Hovold johan@kernel.org

mainline inclusion from mainline-5.4 commit edc4746f253d907d048de680a621e121517f484b category: bugfix bugzilla: NA DTS: NA CVE: CVE-2019-19528

-------------------------------------------------

A recent fix addressing a deadlock on disconnect introduced a new bug by moving the present flag out of the critical section protected by the driver-data mutex. This could lead to a racing release() freeing the driver data before disconnect() is done with it.

Due to insufficient locking a related use-after-free could be triggered also before the above mentioned commit. Specifically, the driver needs to hold the driver-data mutex also while checking the opened flag at disconnect().

Fixes: c468a8aa790e ("usb: iowarrior: fix deadlock on disconnect") Fixes: 946b960d13c1 ("USB: add driver for iowarrior devices.") Cc: stable stable@vger.kernel.org # 2.6.21 Reported-by: syzbot+0761012cebf7bdb38137@syzkaller.appspotmail.com Signed-off-by: Johan Hovold johan@kernel.org Link: https://lore.kernel.org/r/20191009104846.5925-2-johan@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Mao Wenan maowenan@huawei.com --- drivers/usb/misc/iowarrior.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/misc/iowarrior.c b/drivers/usb/misc/iowarrior.c index eb8c08a54a77..7844fd957a8d 100644 --- a/drivers/usb/misc/iowarrior.c +++ b/drivers/usb/misc/iowarrior.c @@ -889,8 +889,6 @@ static void iowarrior_disconnect(struct usb_interface *interface) dev = usb_get_intfdata(interface); mutex_lock(&iowarrior_open_disc_lock); usb_set_intfdata(interface, NULL); - /* prevent device read, write and ioctl */ - dev->present = 0;

minor = dev->minor; mutex_unlock(&iowarrior_open_disc_lock); @@ -901,8 +899,7 @@ static void iowarrior_disconnect(struct usb_interface *interface) mutex_lock(&dev->mutex);

/* prevent device read, write and ioctl */ - - mutex_unlock(&dev->mutex); + dev->present = 0;

if (dev->opened) { /* There is a process that holds a filedescriptor to the device , @@ -912,8 +909,10 @@ static void iowarrior_disconnect(struct usb_interface *interface) usb_kill_urb(dev->int_in_urb); wake_up_interruptible(&dev->read_wait); wake_up_interruptible(&dev->write_wait); + mutex_unlock(&dev->mutex); } else { /* no process is using the device, cleanup now */ + mutex_unlock(&dev->mutex); iowarrior_delete(dev); }