[PATCH 1/4] lkdtm: fix stack protector trigger

[PATCH 1/4] lkdtm: fix stack protector trigger

[Kees Cook]

The -fstack-protector compiler flag will only build stack protections if
a character array is seen. Additionally, the offset to the saved
instruction pointer changes based on architecture, so stomp much harder
(64 bytes) when corrupting the stack.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/misc/lkdtm.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/misc/lkdtm.c b/drivers/misc/lkdtm.c
index 08aad69..adb6bde 100644
--- a/drivers/misc/lkdtm.c
+++ b/drivers/misc/lkdtm.c
@@ -295,10 +295,10 @@ static void lkdtm_do_action(enum ctype which)
 		(void) recursive_loop(0);
 		break;
 	case CT_CORRUPT_STACK: {
-		volatile u32 data[8];
-		volatile u32 *p = data;
+		/* Make sure the compiler creates and uses an 8 char array. */
+		volatile char data[8];
 
-		p[12] = 0x12345678;
+		memset((void *)data, 0, 64);
 		break;
 	}
 	case CT_UNALIGNED_LOAD_STORE_WRITE: {
-- 
1.7.9.5

[PATCH 2/4] lkdtm: add "WARNING" trigger

[Kees Cook]

For additional testing, add "WARNING" as a trigger that calls WARN_ON(1).

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/misc/lkdtm.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/misc/lkdtm.c b/drivers/misc/lkdtm.c
index adb6bde..b1323fc 100644
--- a/drivers/misc/lkdtm.c
+++ b/drivers/misc/lkdtm.c
@@ -68,6 +68,7 @@ enum ctype {
 	CT_NONE,
 	CT_PANIC,
 	CT_BUG,
+	CT_WARNING,
 	CT_EXCEPTION,
 	CT_LOOP,
 	CT_OVERFLOW,
@@ -95,6 +96,7 @@ static char* cp_name[] = {
 static char* cp_type[] = {
 	"PANIC",
 	"BUG",
+	"WARNING",
 	"EXCEPTION",
 	"LOOP",
 	"OVERFLOW",
@@ -284,6 +286,9 @@ static void lkdtm_do_action(enum ctype which)
 	case CT_BUG:
 		BUG();
 		break;
+	case CT_WARNING:
+		WARN_ON(1);
+		break;
 	case CT_EXCEPTION:
 		*((int *) 0) = 0;
 		break;
-- 
1.7.9.5

[PATCH 3/4] lkdtm: add "SPINLOCKUP" trigger

[Kees Cook]

For additional lockup testing, add "SPINLOCKUP" to trigger a spinlock
deadlock when triggered twice.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/misc/lkdtm.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/misc/lkdtm.c b/drivers/misc/lkdtm.c
index b1323fc..8bc7f0b 100644
--- a/drivers/misc/lkdtm.c
+++ b/drivers/misc/lkdtm.c
@@ -78,6 +78,7 @@ enum ctype {
 	CT_WRITE_AFTER_FREE,
 	CT_SOFTLOCKUP,
 	CT_HARDLOCKUP,
+	CT_SPINLOCKUP,
 	CT_HUNG_TASK,
 };
 
@@ -106,6 +107,7 @@ static char* cp_type[] = {
 	"WRITE_AFTER_FREE",
 	"SOFTLOCKUP",
 	"HARDLOCKUP",
+	"SPINLOCKUP",
 	"HUNG_TASK",
 };
 
@@ -123,6 +125,7 @@ static enum cname cpoint = CN_INVALID;
 static enum ctype cptype = CT_NONE;
 static int count = DEFAULT_COUNT;
 static DEFINE_SPINLOCK(count_lock);
+static DEFINE_SPINLOCK(lock_me_up);
 
 module_param(recur_count, int, 0644);
 MODULE_PARM_DESC(recur_count, " Recursion level for the stack overflow test, "\
@@ -345,6 +348,10 @@ static void lkdtm_do_action(enum ctype which)
 		for (;;)
 			cpu_relax();
 		break;
+	case CT_SPINLOCKUP:
+		/* Must be called twice to trigger. */
+		spin_lock(&lock_me_up);
+		break;
 	case CT_HUNG_TASK:
 		set_current_state(TASK_UNINTERRUPTIBLE);
 		schedule();
-- 
1.7.9.5

[PATCH 4/4] lkdtm: add "EXEC_*" triggers

[Kees Cook]

Add new crash locations that attempt to execute non-executable memory
regions (data segment, stack, kmalloc, vmalloc).

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/misc/lkdtm.c |   45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/drivers/misc/lkdtm.c b/drivers/misc/lkdtm.c
index 8bc7f0b..2fc0586 100644
--- a/drivers/misc/lkdtm.c
+++ b/drivers/misc/lkdtm.c
@@ -43,6 +43,7 @@
 #include <linux/slab.h>
 #include <scsi/scsi_cmnd.h>
 #include <linux/debugfs.h>
+#include <linux/vmalloc.h>
 
 #ifdef CONFIG_IDE
 #include <linux/ide.h>
@@ -50,6 +51,7 @@
 
 #define DEFAULT_COUNT 10
 #define REC_NUM_DEFAULT 10
+#define EXEC_SIZE 64
 
 enum cname {
 	CN_INVALID,
@@ -80,6 +82,10 @@ enum ctype {
 	CT_HARDLOCKUP,
 	CT_SPINLOCKUP,
 	CT_HUNG_TASK,
+	CT_EXEC_DATA,
+	CT_EXEC_STACK,
+	CT_EXEC_KMALLOC,
+	CT_EXEC_VMALLOC,
 };
 
 static char* cp_name[] = {
@@ -109,6 +115,10 @@ static char* cp_type[] = {
 	"HARDLOCKUP",
 	"SPINLOCKUP",
 	"HUNG_TASK",
+	"EXEC_DATA",
+	"EXEC_STACK",
+	"EXEC_KMALLOC",
+	"EXEC_VMALLOC",
 };
 
 static struct jprobe lkdtm;
@@ -127,6 +137,8 @@ static int count = DEFAULT_COUNT;
 static DEFINE_SPINLOCK(count_lock);
 static DEFINE_SPINLOCK(lock_me_up);
 
+static u8 data_area[EXEC_SIZE];
+
 module_param(recur_count, int, 0644);
 MODULE_PARM_DESC(recur_count, " Recursion level for the stack overflow test, "\
 				 "default is 10");
@@ -280,6 +292,19 @@ static int recursive_loop(int a)
         	return recursive_loop(a);
 }
 
+static void do_nothing(void)
+{
+	return;
+}
+
+static void execute_location(void *dst)
+{
+	void (*func)(void) = dst;
+
+	memcpy(dst, do_nothing, EXEC_SIZE);
+	func();
+}
+
 static void lkdtm_do_action(enum ctype which)
 {
 	switch (which) {
@@ -356,6 +381,26 @@ static void lkdtm_do_action(enum ctype which)
 		set_current_state(TASK_UNINTERRUPTIBLE);
 		schedule();
 		break;
+	case CT_EXEC_DATA:
+		execute_location(data_area);
+		break;
+	case CT_EXEC_STACK: {
+		u8 stack_area[EXEC_SIZE];
+		execute_location(stack_area);
+		break;
+	}
+	case CT_EXEC_KMALLOC: {
+		u32 *kmalloc_area = kmalloc(EXEC_SIZE, GFP_KERNEL);
+		execute_location(kmalloc_area);
+		kfree(kmalloc_area);
+		break;
+	}
+	case CT_EXEC_VMALLOC: {
+		u32 *vmalloc_area = vmalloc(EXEC_SIZE);
+		execute_location(vmalloc_area);
+		vfree(vmalloc_area);
+		break;
+	}
 	case CT_NONE:
 	default:
 		break;
-- 
1.7.9.5

[PATCH 4/4] lkdtm: add "EXEC_*" triggers

[Kees Cook]

Add new crash locations that attempt to execute non-executable memory
regions (data segment, stack, kmalloc, vmalloc).

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/misc/lkdtm.c |   44 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/drivers/misc/lkdtm.c b/drivers/misc/lkdtm.c
index 8bc7f0b..34712c8 100644
--- a/drivers/misc/lkdtm.c
+++ b/drivers/misc/lkdtm.c
@@ -50,6 +50,7 @@
 
 #define DEFAULT_COUNT 10
 #define REC_NUM_DEFAULT 10
+#define EXEC_SIZE 64
 
 enum cname {
 	CN_INVALID,
@@ -80,6 +81,10 @@ enum ctype {
 	CT_HARDLOCKUP,
 	CT_SPINLOCKUP,
 	CT_HUNG_TASK,
+	CT_EXEC_DATA,
+	CT_EXEC_STACK,
+	CT_EXEC_KMALLOC,
+	CT_EXEC_VMALLOC,
 };
 
 static char* cp_name[] = {
@@ -109,6 +114,10 @@ static char* cp_type[] = {
 	"HARDLOCKUP",
 	"SPINLOCKUP",
 	"HUNG_TASK",
+	"EXEC_DATA",
+	"EXEC_STACK",
+	"EXEC_KMALLOC",
+	"EXEC_VMALLOC",
 };
 
 static struct jprobe lkdtm;
@@ -127,6 +136,8 @@ static int count = DEFAULT_COUNT;
 static DEFINE_SPINLOCK(count_lock);
 static DEFINE_SPINLOCK(lock_me_up);
 
+static u8 data_area[EXEC_SIZE];
+
 module_param(recur_count, int, 0644);
 MODULE_PARM_DESC(recur_count, " Recursion level for the stack overflow test, "\
 				 "default is 10");
@@ -280,6 +291,19 @@ static int recursive_loop(int a)
         	return recursive_loop(a);
 }
 
+static void do_nothing(void)
+{
+	return;
+}
+
+static void execute_location(void *dst)
+{
+	void (*func)(void) = dst;
+
+	memcpy(dst, do_nothing, EXEC_SIZE);
+	func();
+}
+
 static void lkdtm_do_action(enum ctype which)
 {
 	switch (which) {
@@ -356,6 +380,26 @@ static void lkdtm_do_action(enum ctype which)
 		set_current_state(TASK_UNINTERRUPTIBLE);
 		schedule();
 		break;
+	case CT_EXEC_DATA:
+		execute_location(data_area);
+		break;
+	case CT_EXEC_STACK: {
+		u8 stack_area[EXEC_SIZE];
+		execute_location(stack_area);
+		break;
+	}
+	case CT_EXEC_KMALLOC: {
+		u32 *kmalloc_area = kmalloc(EXEC_SIZE, GFP_KERNEL);
+		execute_location(kmalloc_area);
+		kfree(kmalloc_area);
+		break;
+	}
+	case CT_EXEC_VMALLOC: {
+		u32 *vmalloc_area = vmalloc(EXEC_SIZE);
+		execute_location(vmalloc_area);
+		vfree(vmalloc_area);
+		break;
+	}
 	case CT_NONE:
 	default:
 		break;
-- 
1.7.9.5