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

From: [email-masked] (Will Deacon)
Date: Tue, 22 Apr 2014 09:53:07 +0100

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 <[email-masked]>
> Acked-by: Laurent Pinchart <[email-masked]>
> ---
>  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?

Will