Re: [PATCH v2] dma-buf: dma-heap: Add a size check for allocation

[John Stultz <john.stultz@linaro.org>]

On Mon, Dec 27, 2021 at 1:52 AM <guangming.cao@mediatek.com> wrote:
>
> From: Guangming <Guangming.Cao@mediatek.com>
>

Thanks for submitting this!

> Add a size check for allcation since the allocation size is

nit: "allocation" above.

> always less than the total DRAM size.

In general, it might be good to add more context to the commit message
to better answer *why* this change is needed rather than what the
change is doing.  ie: What negative thing happens without this change?
And so how does this change avoid or improve things?


> Signed-off-by: Guangming <Guangming.Cao@mediatek.com>
> Signed-off-by: jianjiao zeng <jianjiao.zeng@mediatek.com>
> ---
> v2: 1. update size limitation as total_dram page size.
>     2. update commit message
> ---
>  drivers/dma-buf/dma-heap.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
> index 56bf5ad01ad5..e39d2be98d69 100644
> --- a/drivers/dma-buf/dma-heap.c
> +++ b/drivers/dma-buf/dma-heap.c
> @@ -55,6 +55,8 @@ static int dma_heap_buffer_alloc(struct dma_heap *heap, size_t len,
>         struct dma_buf *dmabuf;
>         int fd;
>
> +       if (len / PAGE_SIZE > totalram_pages())
> +               return -EINVAL;

This seems sane. I know ION used to have some 1/2 of memory cap to
avoid unnecessary memory pressure on crazy allocations.

Could you send again with an improved commit message?

thanks
-john