[linux-yocto] [PATCH 3/3] x86, kaslr: boot-time selectable with hibernation

[Yang Shi]

From: Kees Cook <keescook at chromium.org>

commit 24f2e0273f80ec262a772059e140a0adef35296d upstream

Changes kASLR from being compile-time selectable (blocked by
CONFIG_HIBERNATION), to being boot-time selectable (with hibernation
available by default) via the "kaslr" kernel command line.

Signed-off-by: Kees Cook <keescook at chromium.org>
Acked-by: Pavel Machek <pavel at ucw.cz>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
Signed-off-by: Yang Shi <yang.shi at windriver.com>
---
 Documentation/kernel-parameters.txt | 11 +++++++----
 arch/x86/Kconfig                    |  1 -
 arch/x86/boot/compressed/aslr.c     |  9 ++++++++-
 kernel/power/hibernate.c            |  6 ++++++
 4 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 580a60c..49e0ac1 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1416,6 +1416,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 	js=		[HW,JOY] Analog joystick
 			See Documentation/input/joystick.txt.
 
+	kaslr/nokaslr	[X86]
+			Enable/disable kernel and module base offset ASLR
+			(Address Space Layout Randomization) if built into
+			the kernel. When CONFIG_HIBERNATION is selected,
+			kASLR is disabled by default. When kASLR is enabled,
+			hibernation will be disabled.
+
 	keepinitrd	[HW,ARM]
 
 	kernelcore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
@@ -2052,10 +2059,6 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 	noapic		[SMP,APIC] Tells the kernel to not make use of any
 			IOAPICs that may be present in the system.
 
-	nokaslr		[X86]
-			Disable kernel and module base offset ASLR (Address
-			Space Layout Randomization) if built into the kernel.
-
 	noautogroup	Disable scheduler automatic task group creation.
 
 	nobats		[PPC] Do not use BATs for mapping kernel lowmem
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 0af5250..402ae4b 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1701,7 +1701,6 @@ config RELOCATABLE
 config RANDOMIZE_BASE
 	bool "Randomize the address of the kernel image"
 	depends on RELOCATABLE
-	depends on !HIBERNATION
 	default n
 	---help---
 	   Randomizes the physical and virtual address at which the
diff --git a/arch/x86/boot/compressed/aslr.c b/arch/x86/boot/compressed/aslr.c
index 4dbf967..fc6091a 100644
--- a/arch/x86/boot/compressed/aslr.c
+++ b/arch/x86/boot/compressed/aslr.c
@@ -289,10 +289,17 @@ unsigned char *choose_kernel_location(unsigned char *input,
 	unsigned long choice = (unsigned long)output;
 	unsigned long random;
 
+#ifdef CONFIG_HIBERNATION
+	if (!cmdline_find_option_bool("kaslr")) {
+		debug_putstr("KASLR disabled by default...\n");
+		goto out;
+	}
+#else
 	if (cmdline_find_option_bool("nokaslr")) {
-		debug_putstr("KASLR disabled...\n");
+		debug_putstr("KASLR disabled by cmdline...\n");
 		goto out;
 	}
+#endif
 
 	/* Record the various known unsafe memory ranges. */
 	mem_avoid_init((unsigned long)input, input_size,
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 37170d4..b713f39 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -1111,9 +1111,15 @@ static int __init resumedelay_setup(char *str)
 	return 1;
 }
 
+static int __init kaslr_nohibernate_setup(char *str)
+{
+	return nohibernate_setup(str);
+}
+
 __setup("noresume", noresume_setup);
 __setup("resume_offset=", resume_offset_setup);
 __setup("resume=", resume_setup);
 __setup("hibernate=", hibernate_setup);
 __setup("resumewait", resumewait_setup);
 __setup("resumedelay=", resumedelay_setup);
+__setup("kaslr", kaslr_nohibernate_setup);
-- 
2.0.2