On 23.03.2017 03:27, Kees Cook wrote:
This is a modified revert of commit 65fe935dd238 ("x86/KASLR, x86/power:
Remove x86 hibernation restrictions"), since it appears that 32-bit
hibernation still can't support KASLR. 64-bit is fine. Since people have
been running with KASLR by default on 32-bit since v4.8, this disables
hibernation (with a warning). Booting with "nokaslr" will disable KASLR
and enable hibernation.
Reported-by: Evgenii Shatokhin <eugene.shatokhin@xxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v4.8+
The patch does not work as intended on my system, unfortunately.
I tried the mainline kernel v4.11-rc3 and added this patch. With
"nokaslr" in the kernel command line, the system fails to hibernate. It
complains this way in the log:
<...>
kernel: PM: writing image.
kernel: PM: Cannot find swap device, try swapon -a.
kernel: PM: Cannot get swap writer
kernel: PM: Basic memory bitmaps freed
kernel: Restarting tasks ... done.
systemd[1]: Time has been changed
systemd[3948]: Time has been changed
systemd[14825]: Time has been changed
systemd[1]: systemd-hibernate.service: main process exited, code=exited,
status=1/FAILURE
systemd[1]: Failed to start Hibernate.
<...>
The swap device (swap file, actually) is available, however:
-------------
# swapon -s
Filename Type Size Used Priority
/swap file 6297596 0 -1
-------------
I built the same kernel without this patch then, added "nokaslr" in the
kernel command line again, and the system hibernates and resumes fine.
---
Documentation/admin-guide/kernel-parameters.txt | 5 +++++
arch/x86/boot/compressed/kaslr.c | 3 +++
kernel/power/hibernate.c | 18 +++++++++++++++++-
3 files changed, 25 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 2ba45caabada..6f899c7f587d 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1725,6 +1725,11 @@
kernel and module base offset ASLR (Address Space
Layout Randomization).
+ On 32-bit x86 with CONFIG_HIBERNATION, hibernation
+ is disabled if KASLR is enabled. If "nokaslr" is
+ specified, KASLR will be diabled and hibernation
+ will be enabled.
+
keepinitrd [HW,ARM]
kernelcore= [KNL,X86,IA-64,PPC]
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 8b7c9e75edcb..b694af45f1e0 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -572,6 +572,9 @@ void choose_random_location(unsigned long input,
return;
}
+ if (IS_ENABLED(CONFIG_X86_32) && IS_ENABLED(CONFIG_HIBERNATION))
+ warn("KASLR active: hibernation disabled on 32-bit x86.");
+
boot_params->hdr.loadflags |= KASLR_FLAG;
/* Prepare to add new identity pagetables on demand. */
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index a8b978c35a6a..1d8f1fe1b7f4 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -37,9 +37,14 @@
#include "power.h"
-static int nocompress;
+#if defined(CONFIG_X86_32) && defined(CONFIG_RANDOMIZE_BASE)
+static int noresume = 1;
+static int nohibernate = 1;
+#else
static int noresume;
static int nohibernate;
+#endif
+static int nocompress;
static int resume_wait;
static unsigned int resume_delay;
static char resume_file[256] = CONFIG_PM_STD_PARTITION;
@@ -1194,3 +1199,14 @@ __setup("hibernate=", hibernate_setup);
__setup("resumewait", resumewait_setup);
__setup("resumedelay=", resumedelay_setup);
__setup("nohibernate", nohibernate_setup);
+
+/* Allow hibernation to be disabled in favor of KASLR on 32-bit x86. */
+#if defined(CONFIG_X86_32) && defined(CONFIG_RANDOMIZE_BASE)
+static int __init nokaslr_hibernate_setup(char *str)
+{
+ noresume = 0;
+ nohibernate = 0;
+ return 1;
+}
+__setup("nokaslr", nokaslr_hibernate_setup);
+#endif
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