On Sun, May 8, 2022 at 5:03 PM Schspa Shi <schspa@xxxxxxxxx> wrote: > > 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@xxxxxxxxxxxxxxxxxxxxxxxxx > Link: https://lore.kernel.org/all/000000000000e66c2805de55b15a@xxxxxxxxxx/ > > Signed-off-by: Schspa Shi <schspa@xxxxxxxxx> > > --- > > Changelog: > v1 -> v2: > - Add a STATE_DEV_REGISTERING as Alan Stern suggested. > v2 -> v3: > - Adjust STATE_DEV_REGISTERING position to reflect the actual > order in which the states occur. > - Add the fault scenarios to comments. > --- > 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 b3be8db1ff63..241740024c50 100644 > --- a/drivers/usb/gadget/legacy/raw_gadget.c > +++ b/drivers/usb/gadget/legacy/raw_gadget.c > @@ -145,6 +145,7 @@ 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 > @@ -508,6 +509,7 @@ 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_register_driver(&dev->driver); > -- > 2.24.3 (Apple Git-128) > Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxx> Thanks, Schspa! Thanks for the review, Alan!
