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USB: iowarrior: fix use-after-free on disconnect 

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: c468a8aa79 ("usb: iowarrior: fix deadlock on disconnect")
Fixes: 946b960d13 ("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>
alistair/sunxi64-5.4-dsi
Johan Hovold 2019-10-09 12:48:41 +02:00 committed by Greg Kroah-Hartman
parent 93ddb1f56a
commit edc4746f25
1 changed files with 3 additions and 4 deletions
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7
drivers/usb/misc/iowarrior.c
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@ -866,8 +866,6 @@ 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);
@ -878,8 +876,7 @@ 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 ,
@ -889,8 +886,10 @@ 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);
}