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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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.