linux-kernel - Re: [patch] Staging: tidspbridge: make mmap root-only so it is not a security problem

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Date:	Sun, 1 Dec 2013 15:27:56 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Pavel Machek <pavel@....cz>
Cc:	Ивайло Димитров 
	<ivo.g.dimitrov.75@...il.com>,
	Pali Rohá <pali.rohar@...il.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Ивайло Д <freemangordon@....bg>,
	sre@...g0.de, omar.ramirez@...itl.com, tony@...mide.com,
	felipe.contreras@...il.com, s-anna@...com, nm@...com,
	ohad@...ery.com, stable@...r.kernel.org,
	linux-kernel@...r.kernel.org, nico@...lde.de
Subject: Re: [patch] Staging: tidspbridge: make mmap root-only so it is not a
 security problem

On Sun, Dec 01, 2013 at 01:10:06PM +0100, Pavel Machek wrote:
> diff --git a/drivers/staging/tidspbridge/rmgr/drv_interface.c b/drivers/staging/tidspbridge/rmgr/drv_interface.c
> index 1aa4a3f..a8e86cf 100644
> --- a/drivers/staging/tidspbridge/rmgr/drv_interface.c
> +++ b/drivers/staging/tidspbridge/rmgr/drv_interface.c
> @@ -258,7 +258,17 @@ err:
>  /* This function maps kernel space memory to user space memory. */
>  static int bridge_mmap(struct file *filp, struct vm_area_struct *vma)
>  {
> -	u32 status;
> +	int status;
> +	struct omap_dsp_platform_data *pdata =
> +	    omap_dspbridge_dev->dev.platform_data;
> +	unsigned long start = vma->vm_pgoff << PAGE_SHIFT;
> +		
> +	if (start < pdata->phys_mempool_base)
> +		return -EINVAL;
> +
> +	if (vma->vm_end - vma->vm_start + (start - pdata->phys_mempool_base) 
> +	    > pdata->phys_mempool_size)

This test is vulnerable to integer overflows if you pick a very high
value for start.  Consider using the vm_iomap_memory() helper function
instead of calling remap_pfn_range() directly.  Commit 7314e613d5ff
('Fix a few incorrectly checked [io_]remap_pfn_range() calls') has an
example of how the conversion works.

regards,
dan carpenter

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