linux-kernel - Re: [PATCH] media: v4l2-core: Fix Oops in ioctl

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Message-ID: <4907cc69-9355-203e-76fc-33fb9452102b@xs4all.nl>
Date:   Wed, 8 Jan 2020 12:12:29 +0100
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Arnd Bergmann <arnd@...db.de>
Cc:     Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Vandana BN <bnvandana@...il.com>, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] media: v4l2-core: Fix Oops in ioctl

Hi Dan,

Marking this as Obsoleted in patchwork since Arnd posted an identical patch for
this already.

Regards,

	Hans

On 1/8/20 11:59 AM, Dan Carpenter wrote:
> Syzbot reported a crash in video_usercopy().  It turns out when we
> broke video_get_user() into a separate function then we accidentally
> moved it outside the if block so it tries to memset a user pointer.
> 
> Reported-by: syzbot+9240c422be249a8422bd@...kaller.appspotmail.com
> Fixes: c8ef1a6076bf ("media: v4l2-core: split out data copy from video_usercopy")
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> ---
> Not actually tested.  :(  Sorry.
> 
>  drivers/media/v4l2-core/v4l2-ioctl.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index b68ff06009cd..aaf83e254272 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -3205,12 +3205,12 @@ video_usercopy(struct file *file, unsigned int orig_cmd, unsigned long arg,
>  			parg = mbuf;
>  		}
>  
> +		err = video_get_user((void __user *)arg, parg, orig_cmd,
> +				     &always_copy);
> +		if (err)
> +			goto out;
>  	}
>  
> -	err = video_get_user((void __user *)arg, parg, orig_cmd, &always_copy);
> -	if (err)
> -		goto out;
> -
>  	err = check_array_args(cmd, parg, &array_size, &user_ptr, &kernel_ptr);
>  	if (err < 0)
>  		goto out;
>