[PATCH v3 6/9] iommu/dma-iommu.c: Convert to use vm_insert_range

[PATCH v3 6/9] iommu/dma-iommu.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>
Reviewed-by: Matthew Wilcox <willy@infradead.org>
---
 drivers/iommu/dma-iommu.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index d1b0475..a2c65e2 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -622,17 +622,10 @@ struct page **iommu_dma_alloc(struct device *dev, size_t size, gfp_t gfp,
 
 int iommu_dma_mmap(struct page **pages, size_t size, struct vm_area_struct *vma)
 {
-	unsigned long uaddr = vma->vm_start;
-	unsigned int i, count = PAGE_ALIGN(size) >> PAGE_SHIFT;
-	int ret = -ENXIO;
+	unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
 
-	for (i = vma->vm_pgoff; i < count && uaddr < vma->vm_end; i++) {
-		ret = vm_insert_page(vma, uaddr, pages[i]);
-		if (ret)
-			break;
-		uaddr += PAGE_SIZE;
-	}
-	return ret;
+	return vm_insert_range(vma, vma->vm_start,
+				pages + vma->vm_pgoff, count);
 }
 
 static dma_addr_t __iommu_dma_map(struct device *dev, phys_addr_t phys,
-- 
1.9.1

Re: [PATCH v3 6/9] iommu/dma-iommu.c: Convert to use vm_insert_range

[Robin Murphy]

On 06/12/2018 18:43, 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>
> Reviewed-by: Matthew Wilcox <willy@infradead.org>
> ---
>   drivers/iommu/dma-iommu.c | 13 +++----------
>   1 file changed, 3 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index d1b0475..a2c65e2 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -622,17 +622,10 @@ struct page **iommu_dma_alloc(struct device *dev, size_t size, gfp_t gfp,
>   
>   int iommu_dma_mmap(struct page **pages, size_t size, struct vm_area_struct *vma)
>   {
> -	unsigned long uaddr = vma->vm_start;
> -	unsigned int i, count = PAGE_ALIGN(size) >> PAGE_SHIFT;
> -	int ret = -ENXIO;
> +	unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
>   
> -	for (i = vma->vm_pgoff; i < count && uaddr < vma->vm_end; i++) {
> -		ret = vm_insert_page(vma, uaddr, pages[i]);
> -		if (ret)
> -			break;
> -		uaddr += PAGE_SIZE;
> -	}
> -	return ret;
> +	return vm_insert_range(vma, vma->vm_start,
> +				pages + vma->vm_pgoff, count);

You also need to adjust count to compensate for the pages skipped by 
vm_pgoff, otherwise you've got an out-of-bounds dereference triggered 
from userspace, which is pretty high up the "not good" scale (not to 
mention the entire call would then propagate -EFAULT back from 
vm_insert_page() and thus always appear to fail for nonzero offsets).

Robin.

>   }
>   
>   static dma_addr_t __iommu_dma_map(struct device *dev, phys_addr_t phys,
> 

Re: [PATCH v3 6/9] iommu/dma-iommu.c: Convert to use vm_insert_range

[Souptick Joarder]

On Fri, Dec 7, 2018 at 7:17 PM Robin Murphy <robin.murphy@arm.com> wrote:
>
> On 06/12/2018 18:43, 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>
> > Reviewed-by: Matthew Wilcox <willy@infradead.org>
> > ---
> >   drivers/iommu/dma-iommu.c | 13 +++----------
> >   1 file changed, 3 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> > index d1b0475..a2c65e2 100644
> > --- a/drivers/iommu/dma-iommu.c
> > +++ b/drivers/iommu/dma-iommu.c
> > @@ -622,17 +622,10 @@ struct page **iommu_dma_alloc(struct device *dev, size_t size, gfp_t gfp,
> >
> >   int iommu_dma_mmap(struct page **pages, size_t size, struct vm_area_struct *vma)
> >   {
> > -     unsigned long uaddr = vma->vm_start;
> > -     unsigned int i, count = PAGE_ALIGN(size) >> PAGE_SHIFT;
> > -     int ret = -ENXIO;
> > +     unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
> >
> > -     for (i = vma->vm_pgoff; i < count && uaddr < vma->vm_end; i++) {
> > -             ret = vm_insert_page(vma, uaddr, pages[i]);
> > -             if (ret)
> > -                     break;
> > -             uaddr += PAGE_SIZE;
> > -     }
> > -     return ret;
> > +     return vm_insert_range(vma, vma->vm_start,
> > +                             pages + vma->vm_pgoff, count);
>
> You also need to adjust count to compensate for the pages skipped by
> vm_pgoff, otherwise you've got an out-of-bounds dereference triggered
> from userspace, which is pretty high up the "not good" scale (not to
> mention the entire call would then propagate -EFAULT back from
> vm_insert_page() and thus always appear to fail for nonzero offsets).

So this should something similar to ->

        return vm_insert_range(vma, vma->vm_start,
                                pages + vma->vm_pgoff, count - vma->vm_pgoff);

Re: [PATCH v3 6/9] iommu/dma-iommu.c: Convert to use vm_insert_range

[Robin Murphy]

On 07/12/2018 20:41, Souptick Joarder wrote:
> On Fri, Dec 7, 2018 at 7:17 PM Robin Murphy <robin.murphy@arm.com> wrote:
>>
>> On 06/12/2018 18:43, 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>
>>> Reviewed-by: Matthew Wilcox <willy@infradead.org>
>>> ---
>>>    drivers/iommu/dma-iommu.c | 13 +++----------
>>>    1 file changed, 3 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
>>> index d1b0475..a2c65e2 100644
>>> --- a/drivers/iommu/dma-iommu.c
>>> +++ b/drivers/iommu/dma-iommu.c
>>> @@ -622,17 +622,10 @@ struct page **iommu_dma_alloc(struct device *dev, size_t size, gfp_t gfp,
>>>
>>>    int iommu_dma_mmap(struct page **pages, size_t size, struct vm_area_struct *vma)
>>>    {
>>> -     unsigned long uaddr = vma->vm_start;
>>> -     unsigned int i, count = PAGE_ALIGN(size) >> PAGE_SHIFT;
>>> -     int ret = -ENXIO;
>>> +     unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
>>>
>>> -     for (i = vma->vm_pgoff; i < count && uaddr < vma->vm_end; i++) {
>>> -             ret = vm_insert_page(vma, uaddr, pages[i]);
>>> -             if (ret)
>>> -                     break;
>>> -             uaddr += PAGE_SIZE;
>>> -     }
>>> -     return ret;
>>> +     return vm_insert_range(vma, vma->vm_start,
>>> +                             pages + vma->vm_pgoff, count);
>>
>> You also need to adjust count to compensate for the pages skipped by
>> vm_pgoff, otherwise you've got an out-of-bounds dereference triggered
>> from userspace, which is pretty high up the "not good" scale (not to
>> mention the entire call would then propagate -EFAULT back from
>> vm_insert_page() and thus always appear to fail for nonzero offsets).
> 
> So this should something similar to ->
> 
>          return vm_insert_range(vma, vma->vm_start,
>                                  pages + vma->vm_pgoff, count - vma->vm_pgoff);
> 

Yup, I think that looks appropriate.

Robin.