[PATCH] arm: dma-mapping: Fix mapping size value

[Ritesh Harjani]

Hi Marek/Will

On Wed, Apr 23, 2014 at 3:00 PM, Laurent Pinchart
<laurent.pinchart at ideasonboard.com> wrote:
> Hi Marek,
>
> On Wednesday 23 April 2014 10:53:24 Marek Szyprowski wrote:
>> On 2014-04-22 10:53, Will Deacon wrote:
>> > On Mon, Apr 21, 2014 at 07:47:27AM +0100, Ritesh Harjani wrote:
>> > > 68efd7d2fb("arm: dma-mapping: remove order parameter from
>> > > arm_iommu_create_mapping()") is causing kernel panic
>> > > because it wrongly sets the value of mapping->size:
>> > >
>> > > Unable to handle kernel NULL pointer dereference at virtual
>> > > address 000000a0
>> > > pgd = e7a84000
>> > > [000000a0] *pgd=00000000
>> > > ...
>> > > PC is at bitmap_clear+0x48/0xd0
>> > > LR is at __iommu_remove_mapping+0x130/0x164
>> > >
>> > > Fix it by correcting mapping->size value.
>> > >
>> > > Signed-off-by: Ritesh Harjani <ritesh.harjani at gmail.com>
>> > > Acked-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
>> > > ---
>> > >
>> > >  arch/arm/mm/dma-mapping.c | 2 +-
>> > >  1 file changed, 1 insertion(+), 1 deletion(-)
>> > >
>> > > diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
>> > > index f62aa06..6b00be1 100644
>> > > --- a/arch/arm/mm/dma-mapping.c
>> > > +++ b/arch/arm/mm/dma-mapping.c
>> > > @@ -1963,8 +1963,8 @@ arm_iommu_create_mapping(struct bus_type *bus,
>> > > dma_addr_t base, size_t size)> >
>> > >   mapping->nr_bitmaps = 1;
>> > >   mapping->extensions = extensions;
>> > >   mapping->base = base;
>> > >
>> > > - mapping->size = bitmap_size << PAGE_SHIFT;
>> > >
>> > >   mapping->bits = BITS_PER_BYTE * bitmap_size;
>> > >
>> > > + mapping->size = mapping->bits << PAGE_SHIFT;
>> >
>> > Ok, but given that mapping->size is derived from mapping->bits, do we
>> > really need both of these fields in struct dma_iommu_mapping?
>>
>> You are right. I didn't notice this while I was refactoring the code.
>> Ritesh, could you update your patch and simply replace all references of
>> mapping->size with (mapping->bits << PAGE_SHIFT), probably with some
>> temporary variable to make the code easier to understand? I've didn't apply
>> your patch yet.
>
> As this patch fixes a v3.15 regression, shouldn't it be applied as-is and
> ASAP, with the cleanup that removes mapping->size coming in a later, less
> urgent patch ?

I agree with Laurent. Anyway this cleanup can be taken care when we will be
doing refactoring of common code to lib/iommu-helper.c.

Anyways, if you still insist I can prepare and submit the patch. Let me know
again on this.

>
> --
> Regards,
>
> Laurent Pinchart
>

Thanks
Ritesh