hibernation: on 32-bit x86, disabled in favor of KASLR

PATCH In review Kees Cook 4 participants 7 messages Mar 23, 2017 – Mar 25, 2017

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Documentation x86 Suspend to RAM Hibernation

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Kees Cook

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2017-03-23 00:27 UTC #0 lore raw

PATCH 1/1 hibernation: on 32-bit x86, disabled in favor of KASLR

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 <[email protected]>

Signed-off-by Kees Cook <[email protected]>

Cc [email protected] # v4.8+

---
 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(-)

Documentation/admin-guide/kernel-parameters.txt +5 -0

index 2ba45caabada..6f899c7f587d 100644
@@ -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]

arch/x86/boot/compressed/kaslr.c +3 -0

index 8b7c9e75edcb..b694af45f1e0 100644
@@ -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. */

kernel/power/hibernate.c +17 -1

index a8b978c35a6a..1d8f1fe1b7f4 100644
@@ -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

Signature · 6 lines

2.7.4


-- 
Kees Cook
Pixel Security

Rafael J. Wysocki

maintainer

2017-03-23 01:10 UTC #1 lore raw

Quoted 10 lines · Kees Cook

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 <[email protected]>
Signed-off-by Kees Cook <[email protected]>
Cc [email protected] # v4.8+

LGTM

Thanks,
Rafael

Evgenii Shatokhin

2017-03-23 13:23 UTC #2 lore raw

In reply to Kees Cook

Quoted 10 lines · Kees Cook

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 <[email protected]>
Signed-off-by Kees Cook <[email protected]>
Cc [email protected] # 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.

Quoted 72 lines

---
  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(-)

Documentation/admin-guide/kernel-parameters.txt +5 -0

index 2ba45caabada..6f899c7f587d 100644
@@ -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]

arch/x86/boot/compressed/kaslr.c +3 -0

index 8b7c9e75edcb..b694af45f1e0 100644
@@ -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. */

kernel/power/hibernate.c +17 -1

index a8b978c35a6a..1d8f1fe1b7f4 100644
@@ -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

Rafael J. Wysocki

maintainer

2017-03-23 15:30 UTC #3 lore raw

Quoted 36 lines · Evgenii Shatokhin

Quoted 11 lines · Kees Cook
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 <[email protected]>
Signed-off-by Kees Cook <[email protected]>
Cc [email protected] # 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:
-------------

Quoted 7 lines

# 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.

With the patch applied and "nokaslr" in the kernel command line, what shows up when you do

$ cat /sys/power/state

Thanks,
Rafael

Evgenii Shatokhin

Tested-by

2017-03-25 14:54 UTC #4 lore raw

Quoted 46 lines · Rafael J. Wysocki

Quoted 36 lines · Evgenii Shatokhin
Quoted 11 lines · Kees Cook
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 <[email protected]>
Signed-off-by Kees Cook <[email protected]>
Cc [email protected] # 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:
-------------
Quoted 7 lines
# 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.

Quoted 6 lines

With the patch applied and "nokaslr" in the kernel command line, what shows up when you do
$ cat /sys/power/state
?

freeze standby mem disk

However, I think now that the patch itself is OK.

I experimented with the patched kernel a bit more and found that hibernate does work when I place "nokaslr" before "resume=xxx resume_offset=xxx" in the kernel command line and does not work when I place "nokaslr" after these options. So I guess there is an issue with parsing of the kernel command line somewhere (dracut scripts? systemd? I do not know). If resume= or resume_offset= were corrupted, that might have been the reason why the system could not find the swap file when hibernating.

Anyway, that issue is clearly unrelated to this patch and the patch itself works OK for me.

Thanks a lot!

Tested-by Evgenii Shatokhin <[email protected]>

Regards,
Evgenii

Kees Cook

author

2017-03-25 17:02 UTC #5 lore raw

Quoted 74 lines · Evgenii Shatokhin

Quoted 53 lines · Rafael J. Wysocki
Quoted 41 lines · Evgenii Shatokhin
Quoted 9 lines · Kees Cook
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.
Quoted 3 lines
Reported-by Evgenii Shatokhin <[email protected]>
Signed-off-by Kees Cook <[email protected]>
Cc [email protected] # 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:
-------------
Quoted 7 lines
# 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.
Quoted 6 lines
With the patch applied and "nokaslr" in the kernel command line, what shows up when you do
$ cat /sys/power/state
?
freeze standby mem disk
However, I think now that the patch itself is OK.
I experimented with the patched kernel a bit more and found that hibernate does work when I place "nokaslr" before "resume=xxx resume_offset=xxx" in the kernel command line and does not work when I place "nokaslr" after these options. So I guess there is an issue with parsing of the kernel command line somewhere (dracut scripts? systemd? I do not know). If resume= or resume_offset= were corrupted, that might have been the reason why the system could not find the swap file when hibernating.

Quoted 6 lines

Anyway, that issue is clearly unrelated to this patch and the patch itself works OK for me.
Thanks a lot!
Tested-by Evgenii Shatokhin <[email protected]>

Ah, right. Hm, that is kind of the fault of the patch (and the prior disabling too). Let me see if I can find a better solution...

-Kees

Signature · 2 lines

Kees Cook
Pixel Security

Yu Chen

2017-03-23 16:38 UTC #6 lore raw

In reply to Evgenii Shatokhin

Hi,

Quoted 14 lines · Evgenii Shatokhin

Quoted 11 lines · Kees Cook
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 <[email protected]>
Signed-off-by Kees Cook <[email protected]>
Cc [email protected] # v4.8+

Quoted 5 lines

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:

Could you please send me your kernel config? I've built a 4.11-rc3 image and runs
it on my 32bit laptop and hibernate works on CONFIG_RANDOMIZE_BASE=y