linux-kernel - [PATCH] init: Move stack canary initialization after setup

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Message-Id: <20170816190906.11098-1-labbott@redhat.com>
Date:   Wed, 16 Aug 2017 12:09:06 -0700
From:   Laura Abbott <labbott@...hat.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Laura Abbott <lauraa@...eaurora.org>, linux-kernel@...r.kernel.org,
        Laura Abbott <labbott@...hat.com>
Subject: [PATCH] init: Move stack canary initialization after setup_arch

From: Laura Abbott <lauraa@...eaurora.org>

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@...eaurora.org>
Signed-off-by: Laura Abbott <labbott@...hat.com>
---
This was a patch I did a while ago as part of some out of tree work to make the
stack canary randomized on arm. The overall work didn't really go anywhere
but there is interest in this part for other approaches to adding randomeness.

I can re-send with more Cc for anyone else who might have opinions.
---
 init/main.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/init/main.c b/init/main.c
index 052481fbe363..c71c4451094c 100644
--- a/init/main.c
+++ b/init/main.c
@@ -515,11 +515,7 @@ 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();
 
@@ -534,6 +530,10 @@ 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 ASAP:
+	 */
+	boot_init_stack_canary();
 	mm_init_cpumask(&init_mm);
 	setup_command_line(command_line);
 	setup_nr_cpu_ids();
-- 
2.13.0