Re: [PATCHv2 1/2] init: Move stack canary initialization after setup_arch

[Kees Cook]

On Wed, Aug 16, 2017 at 3:46 PM, Laura Abbott <labbott@xxxxxxxxxx> wrote:
> From: Laura Abbott <lauraa@xxxxxxxxxxxxxx>
>
> Stack canary intialization involves getting a random number.
> Getting this random number may involve accessing caches or other
> architectural specific features which are not available until
> after the architecture is setup. Move the stack canary initialization
> later to accomodate this.
>
> Signed-off-by: Laura Abbott <lauraa@xxxxxxxxxxxxxx>
> Signed-off-by: Laura Abbott <labbott@xxxxxxxxxx>

Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>

-Kees

> ---
> v2: Also moved add_latent_entropy per suggestion of Kees.
> ---
>  init/main.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/init/main.c b/init/main.c
> index 052481fbe363..21d599eaad06 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -515,12 +515,6 @@ asmlinkage __visible void __init start_kernel(void)
>         smp_setup_processor_id();
>         debug_objects_early_init();
>
> -       /*
> -        * Set up the initial canary ASAP:
> -        */
> -       add_latent_entropy();
> -       boot_init_stack_canary();
> -
>         cgroup_init_early();
>
>         local_irq_disable();
> @@ -534,6 +528,11 @@ asmlinkage __visible void __init start_kernel(void)
>         page_address_init();
>         pr_notice("%s", linux_banner);
>         setup_arch(&command_line);
> +       /*
> +        * Set up the the initial canary and entropy after arch
> +        */
> +       add_latent_entropy();
> +       boot_init_stack_canary();
>         mm_init_cpumask(&init_mm);
>         setup_command_line(command_line);
>         setup_nr_cpu_ids();
> --
> 2.13.0
>



-- 
Kees Cook
Pixel Security