Re: [PATCH v2] staging: android: ion: Zero CMA allocated memory

[Laura Abbott]

On 01/22/2018 09:46 AM, Liam Mark wrote:
> Since commit 204f672255c2 ("staging: android: ion: Use CMA APIs directly")
> the CMA API is now used directly and therefore the allocated memory is no
> longer automatically zeroed.
>
> Explicitly zero CMA allocated memory to ensure that no data is exposed to
> userspace.
>
> Fixes: 204f672255c2 ("staging: android: ion: Use CMA APIs directly")
> Signed-off-by: Liam Mark <lmark@xxxxxxxxxxxxxx>
> ---
> Changes in v2:
>    - Clean up the commit message.
>    - Add 'Fixes:'
>
>   drivers/staging/android/ion/ion_cma_heap.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/drivers/staging/android/ion/ion_cma_heap.c b/drivers/staging/android/ion/ion_cma_heap.c
> index 86196ffd2faf..91a98785607a 100644
> --- a/drivers/staging/android/ion/ion_cma_heap.c
> +++ b/drivers/staging/android/ion/ion_cma_heap.c
> @@ -51,6 +51,8 @@ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer,
>   	if (!pages)
>   		return -ENOMEM;
>   
> +	memset(page_address(pages), 0, size);
> +

This won't work for highmem pages. You need to zero by page via
kmap_atomic in that case. You can use PageHighMem to separate the
paths.

Thanks,
Laura

>   	table = kmalloc(sizeof(*table), GFP_KERNEL);
>   	if (!table)
>   		goto err;