Re: [PATCH v5 2/3] mm: init: report memory auto-initialization features at boot time

Kees Cook
2019-05-29T18:43:12Z

On Wed, May 29, 2019 at 02:38:11PM +0200, Alexander Potapenko wrote:
> Print the currently enabled stack and heap initialization modes.
>
> The possible options for stack are:
> - "all" for CONFIG_INIT_STACK_ALL;
> - "byref_all" for CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL;
> - "byref" for CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF;
> - "__user" for CONFIG_GCC_PLUGIN_STRUCTLEAK_USER;
> - "off" otherwise.
>
> Depending on the values of init_on_alloc and init_on_free boottime
> options we also report "heap alloc" and "heap free" as "on"/"off".
>
> In the init_on_free mode initializing pages at boot time may take some
> time, so print a notice about that as well.
>
> Signed-off-by: Alexander Potapenko <glider@google.com>
> Suggested-by: Kees Cook <keescook@chromium.org>

Looks good to me!

Acked-by: Kees Cook <keescook@chromium.org>

> To: Andrew Morton <akpm@linux-foundation.org>
> To: Christoph Lameter <cl@linux.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Cc: James Morris <jmorris@namei.org>
> Cc: Jann Horn <jannh@google.com>
> Cc: Kostya Serebryany <kcc@google.com>
> Cc: Laura Abbott <labbott@redhat.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Cc: Randy Dunlap <rdunlap@infradead.org>
> Cc: Sandeep Patil <sspatil@android.com>
> Cc: "Serge E. Hallyn" <serge@hallyn.com>
> Cc: Souptick Joarder <jrdr.linux@gmail.com>
> Cc: Marco Elver <elver@google.com>
> Cc: kernel-hardening@lists.openwall.com
> Cc: linux-mm@kvack.org
> Cc: linux-security-module@vger.kernel.org
> ---
> init/main.c | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/init/main.c b/init/main.c
> index 66a196c5e4c3..9d63ff1d48f3 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -520,6 +520,29 @@ static inline void initcall_debug_enable(void)
> }
> #endif
>
> +/* Report memory auto-initialization states for this boot. */
> +void __init report_meminit(void)
> +{
> + const char *stack;
> +
> + if (IS_ENABLED(CONFIG_INIT_STACK_ALL))
> + stack = "all";
> + else if (IS_ENABLED(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL))
> + stack = "byref_all";
> + else if (IS_ENABLED(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF))
> + stack = "byref";
> + else if (IS_ENABLED(CONFIG_GCC_PLUGIN_STRUCTLEAK_USER))
> + stack = "__user";
> + else
> + stack = "off";
> +
> + pr_info("mem auto-init: stack:%s, heap alloc:%s, heap free:%s\n",
> + stack, want_init_on_alloc(GFP_KERNEL) ? "on" : "off",
> + want_init_on_free() ? "on" : "off");
> + if (want_init_on_free())
> + pr_info("Clearing system memory may take some time...\n");
> +}
> +
> /*
> * Set up kernel memory allocators
> */
> @@ -530,6 +553,7 @@ static void __init mm_init(void)
> * bigger than MAX_ORDER unless SPARSEMEM.
> */
> page_ext_init_flatmem();
> + report_meminit();
> mem_init();
> kmem_cache_init();
> pgtable_init();
> --
> 2.22.0.rc1.257.g3120a18244-goog
>

--
Kees Cook