From: Schspa Shi schspa@gmail.com
[ Upstream commit 5f0b5f4d50fa0faa8c76ef9d42a42e8d43f98b44 ]
The usb_gadget_register_driver can be called multi time by to threads via USB_RAW_IOCTL_RUN ioctl syscall, which will lead to multiple registrations.
Call trace: driver_register+0x220/0x3a0 drivers/base/driver.c:171 usb_gadget_register_driver_owner+0xfb/0x1e0 drivers/usb/gadget/udc/core.c:1546 raw_ioctl_run drivers/usb/gadget/legacy/raw_gadget.c:513 [inline] raw_ioctl+0x1883/0x2730 drivers/usb/gadget/legacy/raw_gadget.c:1220 ioctl USB_RAW_IOCTL_RUN
This routine allows two processes to register the same driver instance via ioctl syscall. which lead to a race condition.
Please refer to the following scenarios.
T1 T2 ------------------------------------------------------------------ usb_gadget_register_driver_owner driver_register driver_register driver_find driver_find bus_add_driver bus_add_driver priv alloced <context switch> drv->p = priv; <schedule out> kobject_init_and_add // refcount = 1; //couldn't find an available UDC or it's busy <context switch> priv alloced drv->priv = priv; kobject_init_and_add ---> refcount = 1 <------ // register success <context switch> ===================== another ioctl/process ====================== driver_register driver_find k = kset_find_obj() ---> refcount = 2 <------ <context out> driver_unregister // drv->p become T2's priv ---> refcount = 1 <------ <context switch> kobject_put(k) ---> refcount = 0 <------ return priv->driver; --------UAF here----------
There will be UAF in this scenario.
We can fix it by adding a new STATE_DEV_REGISTERING device state to avoid double register.
Reported-by: syzbot+dc7c3ca638e773db07f6@syzkaller.appspotmail.com Link: https://lore.kernel.org/all/000000000000e66c2805de55b15a@google.com/ Reviewed-by: Andrey Konovalov andreyknvl@gmail.com Signed-off-by: Schspa Shi schspa@gmail.com Link: https://lore.kernel.org/r/20220508150247.38204-1-schspa@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/usb/gadget/legacy/raw_gadget.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/drivers/usb/gadget/legacy/raw_gadget.c b/drivers/usb/gadget/legacy/raw_gadget.c index 33efa6915b91..34cecd3660bf 100644 --- a/drivers/usb/gadget/legacy/raw_gadget.c +++ b/drivers/usb/gadget/legacy/raw_gadget.c @@ -144,6 +144,7 @@ enum dev_state { STATE_DEV_INVALID = 0, STATE_DEV_OPENED, STATE_DEV_INITIALIZED, + STATE_DEV_REGISTERING, STATE_DEV_RUNNING, STATE_DEV_CLOSED, STATE_DEV_FAILED @@ -507,6 +508,7 @@ static int raw_ioctl_run(struct raw_dev *dev, unsigned long value) ret = -EINVAL; goto out_unlock; } + dev->state = STATE_DEV_REGISTERING; spin_unlock_irqrestore(&dev->lock, flags);
ret = usb_gadget_probe_driver(&dev->driver);