linux-kernel - [v4.9 PATCH 4/6] init: move stack canary initialization after setup

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Date:   Sun, 31 Jul 2022 20:26:34 +0200
From:   Hans-Christian Noren Egtvedt <hegtvedt@...co.com>
To:     linux-kernel@...r.kernel.org
Cc:     gregkh@...uxfoundation.org, Laura Abbott <lauraa@...eaurora.org>,
        Laura Abbott <labbott@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        "Theodore Ts'o" <tytso@....edu>,
        Daniel Micay <danielmicay@...il.com>,
        Nick Kralevich <nnk@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [v4.9 PATCH 4/6] init: move stack canary initialization after setup_arch

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

Patch series "Command line randomness", v3.

A series to add the kernel command line as a source of randomness.

This patch (of 2):

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 accommodate this.

Link: http://lkml.kernel.org/r/20170816231458.2299-2-labbott@redhat.com
Signed-off-by: Laura Abbott <lauraa@...eaurora.org>
Signed-off-by: Laura Abbott <labbott@...hat.com>
Acked-by: Kees Cook <keescook@...omium.org>
Cc: "Theodore Ts'o" <tytso@....edu>
Cc: Daniel Micay <danielmicay@...il.com>
Cc: Nick Kralevich <nnk@...gle.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
(cherry picked from commit 121388a31362b0d3176dc1190ac8064b98a61b20)
---
 init/main.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/init/main.c b/init/main.c
index 8b803078d7b..67fa94c5967 100644
--- a/init/main.c
+++ b/init/main.c
@@ -487,12 +487,6 @@ 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();
@@ -506,6 +500,11 @@ 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();
-- 
2.34.1