From: Alan Stern <stern@rowland.harvard.edu>
To: "M. Vefa Bicakci" <m.v.b@runbox.com>
Cc: linux-usb@vger.kernel.org, stable@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Bastien Nocera <hadess@hadess.net>,
Andrey Konovalov <andreyknvl@google.com>,
syzkaller@googlegroups.com
Subject: Re: [PATCH 2/3] usbcore/driver: Fix incorrect downcast
Date: Thu, 17 Sep 2020 11:01:01 -0400 [thread overview]
Message-ID: <20200917150101.GA1088823@rowland.harvard.edu> (raw)
In-Reply-To: <20200917144151.355848-2-m.v.b@runbox.com>
On Thu, Sep 17, 2020 at 05:41:50PM +0300, M. Vefa Bicakci wrote:
> This commit resolves a minor bug in the selection/discovery of more
> specific USB device drivers for devices that are currently bound to
> generic USB device drivers.
>
> The bug is related to the way a candidate USB device driver is
> compared against the generic USB device driver. The code in
> is_dev_usb_generic_driver() assumes that the device driver in question
> is a USB device driver by calling to_usb_device_driver(dev->driver)
> to downcast; however I have observed that this assumption is not always
> true, through code instrumentation.
>
> Given that USB device drivers are bound to struct device instances with
> of the type &usb_device_type, this commit checks the return value of
> is_usb_device() before the call to is_dev_usb_generic_driver(), and
> therefore ensures that incorrect type downcasts do not occur. The use
> of is_usb_device() was suggested by Bastien Nocera.
>
> This bug was found while investigating Andrey Konovalov's report
> indicating USB/IP subsystem's misbehaviour with the generic USB device
> driver matching code.
>
> Fixes: d5643d2249 ("USB: Fix device driver race")
> Link: https://lore.kernel.org/linux-usb/CAAeHK+zOrHnxjRFs=OE8T=O9208B9HP_oo8RZpyVOZ9AJ54pAA@mail.gmail.com/
> Cc: <stable@vger.kernel.org> # 5.8
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Alan Stern <stern@rowland.harvard.edu>
> Cc: Bastien Nocera <hadess@hadess.net>
> Cc: Andrey Konovalov <andreyknvl@google.com>
> Cc: <syzkaller@googlegroups.com>
> Signed-off-by: M. Vefa Bicakci <m.v.b@runbox.com>
> ---
> drivers/usb/core/driver.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
> index 950044a6e77f..ba7acd6e7cc4 100644
> --- a/drivers/usb/core/driver.c
> +++ b/drivers/usb/core/driver.c
> @@ -919,7 +919,7 @@ static int __usb_bus_reprobe_drivers(struct device *dev, void *data)
> struct usb_device *udev;
> int ret;
>
> - if (!is_dev_usb_generic_driver(dev))
> + if (!is_usb_device(dev) || !is_dev_usb_generic_driver(dev))
> return 0;
>
> udev = to_usb_device(dev);
> --
> 2.26.2
Why not simplify the whole thing by testing the underlying driver
pointer?
/* Don't reprobe if current driver isn't usb_generic_driver */
if (dev->driver != &usb_generic_driver.drvwrap.driver)
return 0;
Then is_dev_usb_generic_driver can be removed entirely.
Alan Stern
next prev parent reply other threads:[~2020-09-17 15:08 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-16 13:33 USB driver ID matching broken Andrey Konovalov
2020-09-16 14:15 ` Greg Kroah-Hartman
2020-09-16 14:39 ` Bastien Nocera
2020-09-16 15:58 ` M. Vefa Bicakci
2020-09-17 9:59 ` [PATCH 1/2] usbcore/driver: Fix specific driver selection M. Vefa Bicakci
2020-09-17 9:59 ` [PATCH 2/2] usbip: Make the driver's match function specific M. Vefa Bicakci
2020-09-17 10:23 ` [PATCH 1/2] usbcore/driver: Fix specific driver selection Bastien Nocera
2020-09-17 10:39 ` M. Vefa Bicakci
2020-09-17 10:49 ` Bastien Nocera
2020-09-17 14:41 ` [PATCH 1/3] " M. Vefa Bicakci
2020-09-17 14:41 ` [PATCH 2/3] usbcore/driver: Fix incorrect downcast M. Vefa Bicakci
2020-09-17 15:01 ` Alan Stern [this message]
2020-09-18 9:26 ` M. Vefa Bicakci
2020-09-17 14:41 ` [PATCH 3/3] usbip: Make the driver's match function specific M. Vefa Bicakci
2020-09-17 15:21 ` Shuah Khan
2020-09-18 9:26 ` M. Vefa Bicakci
2020-09-18 14:31 ` M. Vefa Bicakci
2020-09-18 15:49 ` Shuah Khan
2020-09-19 13:54 ` M. Vefa Bicakci
2020-09-21 17:03 ` M. Vefa Bicakci
2020-09-18 14:31 ` [PATCH 1/3] usbcore/driver: Fix specific driver selection M. Vefa Bicakci
2020-09-18 14:52 ` Alan Stern
2020-09-19 13:52 ` M. Vefa Bicakci
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