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 13:10:06 +0100
From:	Pavel Machek <pavel@....cz>
To:	Ивайло Димитров 
	<ivo.g.dimitrov.75@...il.com>
Cc:	Pali Rohá <pali.rohar@...il.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	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

Hi!

> I can (and will) test whatever patches is needed. Also will try to get rid of uuid helpers and send a patch today.
> 

So ... here's patch that you can start from, and that may even work...

Thanks,
									Pavel

Signed-off-by: Pavel Machek <pavel@....cz>

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)
+		return -EINVAL;
 
 	/* VM_IO | VM_DONTEXPAND | VM_DONTDUMP are set by remap_pfn_range() */
 	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
@@ -271,10 +281,10 @@ static int bridge_mmap(struct file *filp, struct vm_area_struct *vma)
 	status = remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
 				 vma->vm_end - vma->vm_start,
 				 vma->vm_page_prot);
-	if (status != 0)
-		status = -EAGAIN;
+	if (status)
+		return -EAGAIN;
 
-	return status;
+	return 0;
 }
 
 static const struct file_operations bridge_fops = {


-- 
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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