linux-kernel - Re: [PATCH] usb: core: Null deref in kernel with USB webcams.

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Date:   Thu, 12 Nov 2020 15:54:17 +0000
From:   John Boero <boeroboy@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Felipe Balbi <balbi@...nel.org>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: core: Null deref in kernel with USB webcams.

Oh for pete's sake.  That patch is backwards.  Sorry.
John

On Thu, Nov 12, 2020 at 3:52 PM John Boero <boeroboy@...il.com> wrote:
>
> From 54f9886454e9a28e8d943c1cef15df9c11555df7 Mon Sep 17 00:00:00 2001
> From: JohnnyB <jboero@...rs.noreply.github.com>
> Date: Thu, 12 Nov 2020 15:28:29 +0000
> Subject: [PATCH] usb: core: Null deref in kernel with USB webcams.
>
> Fixes: Ubuntu Launchpad bug 1827452
>
> This is my first attempt at a kernel contribution so sorry if sloppy.
>
> There is some kind of race condition affecting Logitech
> webcams that crash USB with a null dereference.
> Affects raspberry pi devices as well as x86.
> No check on dev before dereference.
> Simple fix for issue experienced for months in
> both x86 and arm/rpi environments.
>
> Signed-off-by: John Boero <boeroboy@...il.com>
>
> ---
> drivers/usb/core/usb.c | 6 +-----
> 1 file changed, 1 insertion(+), 5 deletions(-)
>
> diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
> index d8756ffe513a..9b4ac4415f1a 100644
> --- a/drivers/usb/core/usb.c
> +++ b/drivers/usb/core/usb.c
> @@ -272,13 +272,9 @@ EXPORT_SYMBOL_GPL(usb_find_alt_setting);
> struct usb_interface *usb_ifnum_to_if(const struct usb_device *dev,
>                                      unsigned ifnum)
> {
> -       struct usb_host_config *config = NULL;
> +       struct usb_host_config *config = dev->actconfig;
>        int i;
>
> -       if (!dev)
> -               return NULL;
> -
> -       config = dev->actconfig;
>        if (!config)
>                return NULL;
>        for (i = 0; i < config->desc.bNumInterfaces; i++)
> --
> 2.26.2