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Subject[PATCH 2/2] x86, kaslr: boot-time selectable with hibernation
Date
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@chromium.org>
---
Documentation/kernel-parameters.txt | 11 +++++++----
arch/x86/Kconfig | 1 -
arch/x86/boot/compressed/aslr.c | 9 ++++++++-
kernel/power/hibernate.c | 7 +++++++
4 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index b9f67781c577..ea0430de1e52 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1464,6 +1464,13 @@ 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
@@ -2100,10 +2107,6 @@ 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 b660088c220d..7fdb639f1b63 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1671,7 +1671,6 @@ 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 4dbf967da50d..fc6091abedb7 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 32672da81114..4aba1621b59c 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -67,6 +67,13 @@ bool hibernation_available(void)
return (hibernation_mode > HIBERNATION_DISABLED);
}

+static int __init parse_kaslr(char *p)
+{
+ hibernation_mode = HIBERNATION_DISABLED;
+ return 0;
+}
+early_param("kaslr", parse_kaslr);
+
/**
* hibernation_set_ops - Set the global hibernate operations.
* @ops: Hibernation operations to use in subsequent hibernation transitions.
--
1.7.9.5


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