linux-kernel - Re: [PATCH v2] HID: leave dev_rdesc unmodified and use it for comparisons

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Date:	Wed, 19 Sep 2012 10:05:01 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	Kevin Daughtridge <kevin@...u.com>
CC:	Jiri Kosina <jkosina@...e.cz>, linux-input@...r.kernel.org,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	Henrik Rydberg <rydberg@...omail.se>
Subject: Re: [PATCH v2] HID: leave dev_rdesc unmodified and use it for comparisons

On 09/19/2012 04:36 AM, Kevin Daughtridge wrote:
> --- a/drivers/hid/hid-core.c
> +++ b/drivers/hid/hid-core.c
> @@ -775,12 +775,14 @@ int hid_open_report(struct hid_device *d
>          return -ENODEV;
>      size = device->dev_rsize;
>  
> +    start = kmemdup(start, size, GFP_KERNEL);
> +    if (start == NULL)
> +        return -ENOMEM;
> +
>      if (device->driver->report_fixup)
>          start = device->driver->report_fixup(device, start, &size);
>  
> -    device->rdesc = kmemdup(start, size, GFP_KERNEL);
> -    if (device->rdesc == NULL)
> -        return -ENOMEM;
> +    device->rdesc = start;
>      device->rsize = size;

AFAICS this is incorrect. Some drivers return pointers to their own
static structure from their .report_fixup. Hence there are two problems:
* leak, because kmemdup'ped start is never freed
* invalid free -- kfree(device->rdesc) will try to free a static structure

regards,
-- 
js
suse labs
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