lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Date:	Wed,  1 Apr 2015 12:59:30 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	X86 ML <x86@...nel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: [PATCH] x86/mm/ASLR: Propagate ASLR status to kernel proper

From: Borislav Petkov <bp@...e.de>

Commit

  e2b32e678513 ("x86, kaslr: randomize module base load address")

made module base address randomization unconditional and didn't regard
disabled KASLR due to CONFIG_HIBERNATION and command line option
"nokaslr". For more info see (now reverted) commit:

  f47233c2d34f ("x86/mm/ASLR: Propagate base load address calculation")

In order to propagate ASLR status to kernel proper, we need a single bit
in boot_params.hdr.loadflags and we've chosen bit 1 thus leaving the
top-down allocated bits for bits supposed to be used by the bootloader.

Originally-by: Jiri Kosina <jkosina@...e.cz>
Suggested-by: "H. Peter Anvin" <hpa@...or.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Borislav Petkov <bp@...e.de>
---
 Documentation/x86/boot.txt            |  6 ++++++
 arch/x86/boot/compressed/aslr.c       |  5 ++++-
 arch/x86/boot/compressed/misc.c       |  5 ++++-
 arch/x86/boot/compressed/misc.h       |  6 ++++--
 arch/x86/include/asm/setup.h          |  5 +++++
 arch/x86/include/uapi/asm/bootparam.h |  1 +
 arch/x86/kernel/module.c              | 11 ++---------
 arch/x86/kernel/setup.c               | 12 ++++++++----
 8 files changed, 34 insertions(+), 17 deletions(-)

diff --git a/Documentation/x86/boot.txt b/Documentation/x86/boot.txt
index a75e3adaa39d..0e1756e680c1 100644
--- a/Documentation/x86/boot.txt
+++ b/Documentation/x86/boot.txt
@@ -406,6 +406,12 @@ Protocol:	2.00+
 	- If 0, the protected-mode code is loaded at 0x10000.
 	- If 1, the protected-mode code is loaded at 0x100000.
 
+  Bit 1 (read): ALSR_FLAG
+	- Used internally by the compressed kernel to communicate
+	  ASLR status to kernel proper.
+	  If 1, ASLR enabled.
+	  If 0, ASLR disabled.
+
   Bit 5 (write): QUIET_FLAG
 	- If 0, print early messages.
 	- If 1, suppress early messages.
diff --git a/arch/x86/boot/compressed/aslr.c b/arch/x86/boot/compressed/aslr.c
index bb1376381985..370e47d763b0 100644
--- a/arch/x86/boot/compressed/aslr.c
+++ b/arch/x86/boot/compressed/aslr.c
@@ -295,7 +295,8 @@ static unsigned long find_random_addr(unsigned long minimum,
 	return slots_fetch_random();
 }
 
-unsigned char *choose_kernel_location(unsigned char *input,
+unsigned char *choose_kernel_location(struct boot_params *boot_params,
+				      unsigned char *input,
 				      unsigned long input_size,
 				      unsigned char *output,
 				      unsigned long output_size)
@@ -315,6 +316,8 @@ unsigned char *choose_kernel_location(unsigned char *input,
 	}
 #endif
 
+	boot_params->hdr.loadflags |= ASLR_FLAG;
+
 	/* Record the various known unsafe memory ranges. */
 	mem_avoid_init((unsigned long)input, input_size,
 		       (unsigned long)output, output_size);
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index a950864a64da..ca83518e405e 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -377,6 +377,9 @@ asmlinkage __visible void *decompress_kernel(void *rmode, memptr heap,
 
 	real_mode = rmode;
 
+	/* Clear it for solely in-kernel use */
+	real_mode->hdr.loadflags &= ~ASLR_FLAG;
+
 	sanitize_boot_params(real_mode);
 
 	if (real_mode->screen_info.orig_video_mode == 7) {
@@ -401,7 +404,7 @@ asmlinkage __visible void *decompress_kernel(void *rmode, memptr heap,
 	 * the entire decompressed kernel plus relocation table, or the
 	 * entire decompressed kernel plus .bss and .brk sections.
 	 */
-	output = choose_kernel_location(input_data, input_len, output,
+	output = choose_kernel_location(real_mode, input_data, input_len, output,
 					output_len > run_size ? output_len
 							      : run_size);
 
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 04477d68403f..89dd0d78013a 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -57,7 +57,8 @@ int cmdline_find_option_bool(const char *option);
 
 #if CONFIG_RANDOMIZE_BASE
 /* aslr.c */
-unsigned char *choose_kernel_location(unsigned char *input,
+unsigned char *choose_kernel_location(struct boot_params *boot_params,
+				      unsigned char *input,
 				      unsigned long input_size,
 				      unsigned char *output,
 				      unsigned long output_size);
@@ -65,7 +66,8 @@ unsigned char *choose_kernel_location(unsigned char *input,
 bool has_cpuflag(int flag);
 #else
 static inline
-unsigned char *choose_kernel_location(unsigned char *input,
+unsigned char *choose_kernel_location(struct boot_params *boot_params,
+				      unsigned char *input,
 				      unsigned long input_size,
 				      unsigned char *output,
 				      unsigned long output_size)
diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h
index ff4e7b236e21..87097428a44d 100644
--- a/arch/x86/include/asm/setup.h
+++ b/arch/x86/include/asm/setup.h
@@ -66,6 +66,11 @@ static inline void x86_ce4100_early_setup(void) { }
  */
 extern struct boot_params boot_params;
 
+static inline bool kaslr_enabled(void)
+{
+	return !!(boot_params.hdr.loadflags & ASLR_FLAG);
+}
+
 /*
  * Do NOT EVER look at the BIOS memory size location.
  * It does not work on many machines.
diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h
index 225b0988043a..cd495e5d7d9d 100644
--- a/arch/x86/include/uapi/asm/bootparam.h
+++ b/arch/x86/include/uapi/asm/bootparam.h
@@ -15,6 +15,7 @@
 
 /* loadflags */
 #define LOADED_HIGH	(1<<0)
+#define ASLR_FLAG	(1<<1)
 #define QUIET_FLAG	(1<<5)
 #define KEEP_SEGMENTS	(1<<6)
 #define CAN_USE_HEAP	(1<<7)
diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index d1ac80b72c72..005c03e93fc5 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -33,6 +33,7 @@
 
 #include <asm/page.h>
 #include <asm/pgtable.h>
+#include <asm/setup.h>
 
 #if 0
 #define DEBUGP(fmt, ...)				\
@@ -47,21 +48,13 @@ do {							\
 
 #ifdef CONFIG_RANDOMIZE_BASE
 static unsigned long module_load_offset;
-static int randomize_modules = 1;
 
 /* Mutex protects the module_load_offset. */
 static DEFINE_MUTEX(module_kaslr_mutex);
 
-static int __init parse_nokaslr(char *p)
-{
-	randomize_modules = 0;
-	return 0;
-}
-early_param("nokaslr", parse_nokaslr);
-
 static unsigned long int get_module_load_offset(void)
 {
-	if (randomize_modules) {
+	if (kaslr_enabled()) {
 		mutex_lock(&module_kaslr_mutex);
 		/*
 		 * Calculate the module_load_offset the first time this
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 5437af09f204..b14cedb1e1ee 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -832,10 +832,14 @@ static void __init trim_low_memory_range(void)
 static int
 dump_kernel_offset(struct notifier_block *self, unsigned long v, void *p)
 {
-	pr_emerg("Kernel Offset: 0x%lx from 0x%lx "
-		 "(relocation range: 0x%lx-0x%lx)\n",
-		 (unsigned long)&_text - __START_KERNEL, __START_KERNEL,
-		 __START_KERNEL_map, MODULES_VADDR-1);
+	if (kaslr_enabled())
+		pr_emerg("Kernel Offset: 0x%lx from 0x%lx (relocation range: 0x%lx-0x%lx)\n",
+			 (unsigned long)&_text - __START_KERNEL,
+			 __START_KERNEL,
+			 __START_KERNEL_map,
+			 MODULES_VADDR-1);
+	else
+		pr_emerg("Kernel Offset: disabled\n");
 
 	return 0;
 }
-- 
2.3.3

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists