Re: [PATCH] kernel: dma: Make CMA boot parameters __ro_after_init

[Robin Murphy]

On 12/10/2019 13:29, Shyam Saini wrote:
> This parameters are not changed after early boot.
> By making them __ro_after_init will reduce any attack surface in the
> kernel.

At a glance, it looks like these are only referenced by a couple of 
__init functions, so couldn't they just be __initdata/__initconst?

Robin.

> Link: https://lwn.net/Articles/676145/
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> Cc: Robin Murphy <robin.murphy@xxxxxxx>
> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> Cc: Christopher Lameter <cl@xxxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Signed-off-by: Shyam Saini <mayhs11saini@xxxxxxxxx>
> ---
>   kernel/dma/contiguous.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
> index 69cfb4345388..1b689b1303cd 100644
> --- a/kernel/dma/contiguous.c
> +++ b/kernel/dma/contiguous.c
> @@ -42,10 +42,10 @@ struct cma *dma_contiguous_default_area;
>    * Users, who want to set the size of global CMA area for their system
>    * should use cma= kernel parameter.
>    */
> -static const phys_addr_t size_bytes = (phys_addr_t)CMA_SIZE_MBYTES * SZ_1M;
> -static phys_addr_t size_cmdline = -1;
> -static phys_addr_t base_cmdline;
> -static phys_addr_t limit_cmdline;
> +static const phys_addr_t __ro_after_init size_bytes = (phys_addr_t)CMA_SIZE_MBYTES * SZ_1M;
> +static phys_addr_t __ro_after_init size_cmdline = -1;
> +static phys_addr_t __ro_after_init base_cmdline;
> +static phys_addr_t __ro_after_init limit_cmdline;
>   
>   static int __init early_cma(char *p)
>   {