Re: [PATCH RESEND] USB HID: Protect against disconnect/NULL-dereference race

From: Amit Nagal <helloin.amit-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: Jiri Kosina <jkosina-AlSwsSmVLrQ@public.gmane.org>,
	linux-input-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Chris Ball <cjb-2X9k7bc8m7Mdnm+yROfE0A@public.gmane.org>
Subject: Re: [PATCH RESEND] USB HID: Protect against disconnect/NULL-dereference race
Date: Fri, 13 Aug 2010 14:25:52 +0530	[thread overview]
Message-ID: <AANLkTim_Jj0w22AM0O=PoF01DHFe+VMvjmvi4nqVnqNx@mail.gmail.com> (raw)
In-Reply-To: <m3lj8b8m6b.fsf-0VGQAjvlmrQzNDMTQreKSUB+6BGkLq7r@public.gmane.org>

Hi ,

i am also using HIDDEV interface . and i also got hiddev_ioctl NULL
dereference problem .

Below  patch fixes my problem .

Regards
Amit Nagal

On Fri, Aug 13, 2010 at 4:37 AM, Chris Ball <cjb-2X9k7bc8m7Mdnm+yROfE0A@public.gmane.org> wrote:
> One of our users reports consistently hitting a NULL dereference that
> resolves to the "hid_to_usb_dev(hid);" call in hiddev_ioctl(), when
> disconnecting a Lego WeDo USB HID device from an OLPC XO running
> Scratch software.  There's a FIXME comment and a guard against the
> dereference, but that happens farther down the function than the
> initial dereference does.
>
> This patch moves the call to be below the guard, and the user reports
> that it fixes the problem for him.  OLPC bug report:
> http://dev.laptop.org/ticket/10174
>
> Signed-off-by: Chris Ball <cjb-2X9k7bc8m7Mdnm+yROfE0A@public.gmane.org>
> ---
>  drivers/hid/usbhid/hiddev.c |    6 ++++--
>  1 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/hid/usbhid/hiddev.c b/drivers/hid/usbhid/hiddev.c
> index c24d2fa..7ec009a 100644
> --- a/drivers/hid/usbhid/hiddev.c
> +++ b/drivers/hid/usbhid/hiddev.c
> @@ -593,7 +593,7 @@ static long hiddev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>        struct hiddev_list *list = file->private_data;
>        struct hiddev *hiddev = list->hiddev;
>        struct hid_device *hid = hiddev->hid;
> -       struct usb_device *dev = hid_to_usb_dev(hid);
> +       struct usb_device *dev;
>        struct hiddev_collection_info cinfo;
>        struct hiddev_report_info rinfo;
>        struct hiddev_field_info finfo;
> @@ -607,9 +607,11 @@ static long hiddev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>        /* Called without BKL by compat methods so no BKL taken */
>
>        /* FIXME: Who or what stop this racing with a disconnect ?? */
> -       if (!hiddev->exist)
> +       if (!hiddev->exist || !hid)
>                return -EIO;
>
> +       dev = hid_to_usb_dev(hid);
> +
>        switch (cmd) {
>
>        case HIDIOCGVERSION:
> --
> 1.7.0.1
>
> --
> Chris Ball   <cjb-2X9k7bc8m7Mdnm+yROfE0A@public.gmane.org>
> One Laptop Per Child
> --
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