[PATCH v4 2/9] arch/arm/mm/dma-mapping.c: Convert to use vm_insert_range

[PATCH v4 2/9] arch/arm/mm/dma-mapping.c: Convert to use vm_insert_range

[Souptick Joarder]

Convert to use vm_insert_range() to map range of kernel
memory to user vma.

Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
---
 arch/arm/mm/dma-mapping.c | 21 +++++++--------------
 1 file changed, 7 insertions(+), 14 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 661fe48..7cbcde5 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -1582,31 +1582,24 @@ static int __arm_iommu_mmap_attrs(struct device *dev, struct vm_area_struct *vma
 		    void *cpu_addr, dma_addr_t dma_addr, size_t size,
 		    unsigned long attrs)
 {
-	unsigned long uaddr = vma->vm_start;
-	unsigned long usize = vma->vm_end - vma->vm_start;
+	unsigned long page_count = vma_pages(vma);
 	struct page **pages = __iommu_get_pages(cpu_addr, attrs);
 	unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
 	unsigned long off = vma->vm_pgoff;
+	int err;
 
 	if (!pages)
 		return -ENXIO;
 
-	if (off >= nr_pages || (usize >> PAGE_SHIFT) > nr_pages - off)
+	if (off >= nr_pages)
 		return -ENXIO;
 
 	pages += off;
+	err = vm_insert_range(vma, vma->vm_start, pages, page_count);
+	if (err)
+		pr_err("Remapping memory failed: %d\n", err);
 
-	do {
-		int ret = vm_insert_page(vma, uaddr, *pages++);
-		if (ret) {
-			pr_err("Remapping memory failed: %d\n", ret);
-			return ret;
-		}
-		uaddr += PAGE_SIZE;
-		usize -= PAGE_SIZE;
-	} while (usize > 0);
-
-	return 0;
+	return err;
 }
 static int arm_iommu_mmap_attrs(struct device *dev,
 		struct vm_area_struct *vma, void *cpu_addr,
-- 
1.9.1


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Re: [PATCH v4 2/9] arch/arm/mm/dma-mapping.c: Convert to use vm_insert_range

[Russell King - ARM Linux]

On Tue, Dec 18, 2018 at 01:52:09AM +0530, Souptick Joarder wrote:
> Convert to use vm_insert_range() to map range of kernel
> memory to user vma.
> 
> Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
> ---
>  arch/arm/mm/dma-mapping.c | 21 +++++++--------------
>  1 file changed, 7 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index 661fe48..7cbcde5 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -1582,31 +1582,24 @@ static int __arm_iommu_mmap_attrs(struct device *dev, struct vm_area_struct *vma
>  		    void *cpu_addr, dma_addr_t dma_addr, size_t size,
>  		    unsigned long attrs)
>  {
> -	unsigned long uaddr = vma->vm_start;
> -	unsigned long usize = vma->vm_end - vma->vm_start;
> +	unsigned long page_count = vma_pages(vma);
>  	struct page **pages = __iommu_get_pages(cpu_addr, attrs);
>  	unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
>  	unsigned long off = vma->vm_pgoff;
> +	int err;
>  
>  	if (!pages)
>  		return -ENXIO;
>  
> -	if (off >= nr_pages || (usize >> PAGE_SHIFT) > nr_pages - off)
> +	if (off >= nr_pages)
>  		return -ENXIO;

Are you sure you can make this change?

You are restricting the offset to be within 0..nr_pages which ensures
that the initial struct page that is passed to vm_insert_range() is
valid, but I think the removal of the following check is unsafe.

Your new vm_insert_range() function only checks page_count <=
vma_pages(vma), which it will be since it _is_ vma_pages(vma).  With
the removal of the second condition, there will be nothing checking
that (eg) off may be nr_pages - 1, and page_count=50, meaning that
vm_insert_range() will walk off the end of the page array.

Please take another look at this.

What about the other callsites of your new function - do they have
the same issue?

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
According to speedtest.net: 11.9Mbps down 500kbps up

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Re: [PATCH v4 2/9] arch/arm/mm/dma-mapping.c: Convert to use vm_insert_range

[Souptick Joarder]

On Tue, Dec 18, 2018 at 3:08 PM Russell King - ARM Linux
<linux@armlinux.org.uk> wrote:
>
> On Tue, Dec 18, 2018 at 01:52:09AM +0530, Souptick Joarder wrote:
> > Convert to use vm_insert_range() to map range of kernel
> > memory to user vma.
> >
> > Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
> > ---
> >  arch/arm/mm/dma-mapping.c | 21 +++++++--------------
> >  1 file changed, 7 insertions(+), 14 deletions(-)
> >
> > diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> > index 661fe48..7cbcde5 100644
> > --- a/arch/arm/mm/dma-mapping.c
> > +++ b/arch/arm/mm/dma-mapping.c
> > @@ -1582,31 +1582,24 @@ static int __arm_iommu_mmap_attrs(struct device *dev, struct vm_area_struct *vma
> >                   void *cpu_addr, dma_addr_t dma_addr, size_t size,
> >                   unsigned long attrs)
> >  {
> > -     unsigned long uaddr = vma->vm_start;
> > -     unsigned long usize = vma->vm_end - vma->vm_start;
> > +     unsigned long page_count = vma_pages(vma);
> >       struct page **pages = __iommu_get_pages(cpu_addr, attrs);
> >       unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
> >       unsigned long off = vma->vm_pgoff;
> > +     int err;
> >
> >       if (!pages)
> >               return -ENXIO;
> >
> > -     if (off >= nr_pages || (usize >> PAGE_SHIFT) > nr_pages - off)
> > +     if (off >= nr_pages)
> >               return -ENXIO;
>
> Are you sure you can make this change?
>
> You are restricting the offset to be within 0..nr_pages which ensures
> that the initial struct page that is passed to vm_insert_range() is
> valid, but I think the removal of the following check is unsafe.
>
> Your new vm_insert_range() function only checks page_count <=
> vma_pages(vma), which it will be since it _is_ vma_pages(vma).  With
> the removal of the second condition, there will be nothing checking
> that (eg) off may be nr_pages - 1, and page_count=50, meaning that
> vm_insert_range() will walk off the end of the page array.
>
> Please take another look at this.

This check shouldn't be removed.
>
> What about the other callsites of your new function - do they have
> the same issue?

I think other callsites don't have the same issue.

>
> --
> RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
> FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
> According to speedtest.net: 11.9Mbps down 500kbps up

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