From: Kees Cook <keescook@chromium.org>
To: Alexander Potapenko <glider@google.com>
Cc: akpm@linux-foundation.org, cl@linux.com,
kernel-hardening@lists.openwall.com,
Masahiro Yamada <yamada.masahiro@socionext.com>,
James Morris <jmorris@namei.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Kostya Serebryany <kcc@google.com>,
Dmitry Vyukov <dvyukov@google.com>,
Sandeep Patil <sspatil@android.com>,
Laura Abbott <labbott@redhat.com>,
Randy Dunlap <rdunlap@infradead.org>,
Jann Horn <jannh@google.com>, Mark Rutland <mark.rutland@arm.com>,
linux-mm@kvack.org, linux-security-module@vger.kernel.org
Subject: Re: [PATCH v2 1/4] mm: security: introduce init_on_alloc=1 and init_on_free=1 boot options
Date: Thu, 16 May 2019 09:19:56 -0700 [thread overview]
Message-ID: <201905160907.92FAC880@keescook> (raw)
In-Reply-To: <20190514143537.10435-2-glider@google.com>
On Tue, May 14, 2019 at 04:35:34PM +0200, Alexander Potapenko wrote:
> Slowdown for the new features compared to init_on_free=0,
> init_on_alloc=0:
>
> hackbench, init_on_free=1: +7.62% sys time (st.err 0.74%)
> hackbench, init_on_alloc=1: +7.75% sys time (st.err 2.14%)
I wonder if the patch series should be reorganized to introduce
__GFP_NO_AUTOINIT first, so that when the commit with benchmarks appears,
we get the "final" numbers...
> Linux build with -j12, init_on_free=1: +8.38% wall time (st.err 0.39%)
> Linux build with -j12, init_on_free=1: +24.42% sys time (st.err 0.52%)
> Linux build with -j12, init_on_alloc=1: -0.13% wall time (st.err 0.42%)
> Linux build with -j12, init_on_alloc=1: +0.57% sys time (st.err 0.40%)
I'm working on reproducing these benchmarks. I'd really like to narrow
down the +24% number here. But it does
> The slowdown for init_on_free=0, init_on_alloc=0 compared to the
> baseline is within the standard error.
I think the use of static keys here is really great: this is available
by default for anyone that wants to turn it on.
I'm thinking, given the configuable nature of this, it'd be worth adding
a little more detail at boot time. I think maybe a separate patch could
be added to describe the kernel's memory auto-initialization features,
and add something like this to mm_init():
+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";
+
+ /* Report memory auto-initialization states for this boot. */
+ 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");
+}
To get a boot line like:
mem auto-init: stack:off, heap alloc:off, heap free:on
And one other thought I had was that in the init_on_free=1 case, there is
a large pause at boot while memory is being cleared. I think it'd be handy
to include a comment about that, just to keep people from being surprised:
diff --git a/init/main.c b/init/main.c
index cf0c3948ce0e..aea278392338 100644
--- a/init/main.c
+++ b/init/main.c
@@ -529,6 +529,8 @@ static void __init mm_init(void)
* bigger than MAX_ORDER unless SPARSEMEM.
*/
page_ext_init_flatmem();
+ if (want_init_on_free())
+ pr_info("Clearing system memory ...\n");
mem_init();
kmem_cache_init();
pgtable_init();
Beyond these thoughts, I think this series is in good shape.
Andrew (or anyone else) do you have any concerns about this?
--
Kees Cook
next prev parent reply other threads:[~2019-05-16 16:20 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190514143537.10435-1-glider@google.com>
2019-05-14 14:35 ` [PATCH v2 1/4] mm: security: introduce init_on_alloc=1 and init_on_free=1 boot options Alexander Potapenko
2019-05-16 16:19 ` Kees Cook [this message]
2019-05-16 16:42 ` Alexander Potapenko
2019-05-16 17:03 ` Kees Cook
2019-05-17 1:26 ` Kees Cook
2019-05-17 14:38 ` Alexander Potapenko
2019-05-17 14:04 ` Michal Hocko
2019-05-17 14:11 ` Alexander Potapenko
2019-05-17 14:20 ` Michal Hocko
2019-05-17 16:36 ` Kees Cook
2019-05-17 17:11 ` Michal Hocko
2019-05-14 14:35 ` [PATCH v2 2/4] lib: introduce test_meminit module Alexander Potapenko
2019-05-16 1:02 ` Kees Cook
2019-05-17 15:51 ` Alexander Potapenko
2019-05-17 16:37 ` Kees Cook
2019-05-14 14:35 ` [PATCH v2 3/4] gfp: mm: introduce __GFP_NO_AUTOINIT Alexander Potapenko
2019-05-17 12:59 ` Michal Hocko
2019-05-17 13:18 ` Alexander Potapenko
2019-05-17 13:25 ` Michal Hocko
2019-05-17 13:37 ` Alexander Potapenko
2019-05-17 14:01 ` Michal Hocko
2019-05-17 16:27 ` Kees Cook
2019-05-17 17:11 ` Michal Hocko
2019-05-21 14:18 ` Alexander Potapenko
2019-05-21 14:25 ` Michal Hocko
2019-05-14 14:35 ` [PATCH v2 4/4] net: apply __GFP_NO_AUTOINIT to AF_UNIX sk_buff allocations Alexander Potapenko
2019-05-16 16:53 ` Kees Cook
2019-05-17 0:26 ` Kees Cook
2019-05-17 8:49 ` Alexander Potapenko
2019-05-17 13:50 ` Alexander Potapenko
2019-05-17 16:13 ` Kees Cook
2019-05-17 0:50 ` [PATCH 5/4] mm: Introduce SLAB_NO_FREE_INIT and mark excluded caches Kees Cook
2019-05-17 8:34 ` Alexander Potapenko
2019-05-17 15:59 ` Kees Cook
2019-05-20 6:10 ` Mathias Krause
2019-05-20 16:12 ` Kees Cook
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