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Commit a3dff71c authored by Kees Cook's avatar Kees Cook
Browse files

lkdtm: split usercopy tests to separate file 



This splits the USERCOPY_* tests into the new lkdtm_usercopy.c file to
help separate things better for readability.

Signed-off-by: default avatarKees Cook <keescook@chromium.org>
parent 0edca7b5

drivers/misc/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -60,6 +60,7 @@ obj-$(CONFIG_PANEL) += panel.o 


lkdtm-$(CONFIG_LKDTM)		+= lkdtm_core.o

lkdtm-$(CONFIG_LKDTM)		+= lkdtm_rodata_objcopy.o

lkdtm-$(CONFIG_LKDTM)		+= lkdtm_usercopy.o



OBJCOPYFLAGS :=

OBJCOPYFLAGS_lkdtm_rodata_objcopy.o := \

drivers/misc/lkdtm.h

+13 −0
Original line number Diff line number Diff line 
#ifndef __LKDTM_H

#define __LKDTM_H



/* lkdtm_rodata.c */

void lkdtm_rodata_do_nothing(void);



/* lkdtm_usercopy.c */

void __init lkdtm_usercopy_init(void);

void __exit lkdtm_usercopy_exit(void);

void lkdtm_USERCOPY_HEAP_SIZE_TO(void);

void lkdtm_USERCOPY_HEAP_SIZE_FROM(void);

void lkdtm_USERCOPY_HEAP_FLAG_TO(void);

void lkdtm_USERCOPY_HEAP_FLAG_FROM(void);

void lkdtm_USERCOPY_STACK_FRAME_TO(void);

void lkdtm_USERCOPY_STACK_FRAME_FROM(void);

void lkdtm_USERCOPY_STACK_BEYOND(void);

void lkdtm_USERCOPY_KERNEL(void);



#endif

drivers/misc/lkdtm_core.c

+13 −266
Original line number Diff line number Diff line
@@ -193,10 +193,6 @@ static DEFINE_SPINLOCK(lock_me_up); 


static u8 data_area[EXEC_SIZE];



static size_t cache_size = 1024;

static struct kmem_cache *bad_cache;



static const unsigned char test_text[] = "This is a test.\n";

static const unsigned long rodata = 0xAA55AA55;

static unsigned long ro_after_init __ro_after_init = 0x55AA5500;
@@ -403,255 +399,6 @@ static void execute_user_location(void *dst) 
	func();

}



/*

 * Instead of adding -Wno-return-local-addr, just pass the stack address

 * through a function to obfuscate it from the compiler.

 */

static noinline unsigned char *trick_compiler(unsigned char *stack)

{

	return stack + 0;

}



static noinline unsigned char *do_usercopy_stack_callee(int value)

{

	unsigned char buf[32];

	int i;



	/* Exercise stack to avoid everything living in registers. */

	for (i = 0; i < sizeof(buf); i++) {

		buf[i] = value & 0xff;

	}



	return trick_compiler(buf);

}



static noinline void do_usercopy_stack(bool to_user, bool bad_frame)

{

	unsigned long user_addr;

	unsigned char good_stack[32];

	unsigned char *bad_stack;

	int i;



	/* Exercise stack to avoid everything living in registers. */

	for (i = 0; i < sizeof(good_stack); i++)

		good_stack[i] = test_text[i % sizeof(test_text)];



	/* This is a pointer to outside our current stack frame. */

	if (bad_frame) {

		bad_stack = do_usercopy_stack_callee((uintptr_t)bad_stack);

	} else {

		/* Put start address just inside stack. */

		bad_stack = task_stack_page(current) + THREAD_SIZE;

		bad_stack -= sizeof(unsigned long);

	}



	user_addr = vm_mmap(NULL, 0, PAGE_SIZE,

			    PROT_READ | PROT_WRITE | PROT_EXEC,

			    MAP_ANONYMOUS | MAP_PRIVATE, 0);

	if (user_addr >= TASK_SIZE) {

		pr_warn("Failed to allocate user memory\n");

		return;

	}



	if (to_user) {

		pr_info("attempting good copy_to_user of local stack\n");

		if (copy_to_user((void __user *)user_addr, good_stack,

				 sizeof(good_stack))) {

			pr_warn("copy_to_user failed unexpectedly?!\n");

			goto free_user;

		}



		pr_info("attempting bad copy_to_user of distant stack\n");

		if (copy_to_user((void __user *)user_addr, bad_stack,

				 sizeof(good_stack))) {

			pr_warn("copy_to_user failed, but lacked Oops\n");

			goto free_user;

		}

	} else {

		/*

		 * There isn't a safe way to not be protected by usercopy

		 * if we're going to write to another thread's stack.

		 */

		if (!bad_frame)

			goto free_user;



		pr_info("attempting good copy_from_user of local stack\n");

		if (copy_from_user(good_stack, (void __user *)user_addr,

				   sizeof(good_stack))) {

			pr_warn("copy_from_user failed unexpectedly?!\n");

			goto free_user;

		}



		pr_info("attempting bad copy_from_user of distant stack\n");

		if (copy_from_user(bad_stack, (void __user *)user_addr,

				   sizeof(good_stack))) {

			pr_warn("copy_from_user failed, but lacked Oops\n");

			goto free_user;

		}

	}



free_user:

	vm_munmap(user_addr, PAGE_SIZE);

}



static void do_usercopy_kernel(void)

{

	unsigned long user_addr;



	user_addr = vm_mmap(NULL, 0, PAGE_SIZE,

			    PROT_READ | PROT_WRITE | PROT_EXEC,

			    MAP_ANONYMOUS | MAP_PRIVATE, 0);

	if (user_addr >= TASK_SIZE) {

		pr_warn("Failed to allocate user memory\n");

		return;

	}



	pr_info("attempting good copy_to_user from kernel rodata\n");

	if (copy_to_user((void __user *)user_addr, test_text,

			 sizeof(test_text))) {

		pr_warn("copy_to_user failed unexpectedly?!\n");

		goto free_user;

	}



	pr_info("attempting bad copy_to_user from kernel text\n");

	if (copy_to_user((void __user *)user_addr, vm_mmap, PAGE_SIZE)) {

		pr_warn("copy_to_user failed, but lacked Oops\n");

		goto free_user;

	}



free_user:

	vm_munmap(user_addr, PAGE_SIZE);

}



static void do_usercopy_heap_size(bool to_user)

{

	unsigned long user_addr;

	unsigned char *one, *two;

	size_t size = 1024;



	one = kmalloc(size, GFP_KERNEL);

	two = kmalloc(size, GFP_KERNEL);

	if (!one || !two) {

		pr_warn("Failed to allocate kernel memory\n");

		goto free_kernel;

	}



	user_addr = vm_mmap(NULL, 0, PAGE_SIZE,

			    PROT_READ | PROT_WRITE | PROT_EXEC,

			    MAP_ANONYMOUS | MAP_PRIVATE, 0);

	if (user_addr >= TASK_SIZE) {

		pr_warn("Failed to allocate user memory\n");

		goto free_kernel;

	}



	memset(one, 'A', size);

	memset(two, 'B', size);



	if (to_user) {

		pr_info("attempting good copy_to_user of correct size\n");

		if (copy_to_user((void __user *)user_addr, one, size)) {

			pr_warn("copy_to_user failed unexpectedly?!\n");

			goto free_user;

		}



		pr_info("attempting bad copy_to_user of too large size\n");

		if (copy_to_user((void __user *)user_addr, one, 2 * size)) {

			pr_warn("copy_to_user failed, but lacked Oops\n");

			goto free_user;

		}

	} else {

		pr_info("attempting good copy_from_user of correct size\n");

		if (copy_from_user(one, (void __user *)user_addr, size)) {

			pr_warn("copy_from_user failed unexpectedly?!\n");

			goto free_user;

		}



		pr_info("attempting bad copy_from_user of too large size\n");

		if (copy_from_user(one, (void __user *)user_addr, 2 * size)) {

			pr_warn("copy_from_user failed, but lacked Oops\n");

			goto free_user;

		}

	}



free_user:

	vm_munmap(user_addr, PAGE_SIZE);

free_kernel:

	kfree(one);

	kfree(two);

}



static void do_usercopy_heap_flag(bool to_user)

{

	unsigned long user_addr;

	unsigned char *good_buf = NULL;

	unsigned char *bad_buf = NULL;



	/* Make sure cache was prepared. */

	if (!bad_cache) {

		pr_warn("Failed to allocate kernel cache\n");

		return;

	}



	/*

	 * Allocate one buffer from each cache (kmalloc will have the

	 * SLAB_USERCOPY flag already, but "bad_cache" won't).

	 */

	good_buf = kmalloc(cache_size, GFP_KERNEL);

	bad_buf = kmem_cache_alloc(bad_cache, GFP_KERNEL);

	if (!good_buf || !bad_buf) {

		pr_warn("Failed to allocate buffers from caches\n");

		goto free_alloc;

	}



	/* Allocate user memory we'll poke at. */

	user_addr = vm_mmap(NULL, 0, PAGE_SIZE,

			    PROT_READ | PROT_WRITE | PROT_EXEC,

			    MAP_ANONYMOUS | MAP_PRIVATE, 0);

	if (user_addr >= TASK_SIZE) {

		pr_warn("Failed to allocate user memory\n");

		goto free_alloc;

	}



	memset(good_buf, 'A', cache_size);

	memset(bad_buf, 'B', cache_size);



	if (to_user) {

		pr_info("attempting good copy_to_user with SLAB_USERCOPY\n");

		if (copy_to_user((void __user *)user_addr, good_buf,

				 cache_size)) {

			pr_warn("copy_to_user failed unexpectedly?!\n");

			goto free_user;

		}



		pr_info("attempting bad copy_to_user w/o SLAB_USERCOPY\n");

		if (copy_to_user((void __user *)user_addr, bad_buf,

				 cache_size)) {

			pr_warn("copy_to_user failed, but lacked Oops\n");

			goto free_user;

		}

	} else {

		pr_info("attempting good copy_from_user with SLAB_USERCOPY\n");

		if (copy_from_user(good_buf, (void __user *)user_addr,

				   cache_size)) {

			pr_warn("copy_from_user failed unexpectedly?!\n");

			goto free_user;

		}



		pr_info("attempting bad copy_from_user w/o SLAB_USERCOPY\n");

		if (copy_from_user(bad_buf, (void __user *)user_addr,

				   cache_size)) {

			pr_warn("copy_from_user failed, but lacked Oops\n");

			goto free_user;

		}

	}



free_user:

	vm_munmap(user_addr, PAGE_SIZE);

free_alloc:

	if (bad_buf)

		kmem_cache_free(bad_cache, bad_buf);

	kfree(good_buf);

}



static void lkdtm_do_action(enum ctype which)

{
@@ -964,28 +711,28 @@ static void lkdtm_do_action(enum ctype which) 
		return;

	}

	case CT_USERCOPY_HEAP_SIZE_TO:

		do_usercopy_heap_size(true);

		lkdtm_USERCOPY_HEAP_SIZE_TO();

		break;

	case CT_USERCOPY_HEAP_SIZE_FROM:

		do_usercopy_heap_size(false);

		lkdtm_USERCOPY_HEAP_SIZE_FROM();

		break;

	case CT_USERCOPY_HEAP_FLAG_TO:

		do_usercopy_heap_flag(true);

		lkdtm_USERCOPY_HEAP_FLAG_TO();

		break;

	case CT_USERCOPY_HEAP_FLAG_FROM:

		do_usercopy_heap_flag(false);

		lkdtm_USERCOPY_HEAP_FLAG_FROM();

		break;

	case CT_USERCOPY_STACK_FRAME_TO:

		do_usercopy_stack(true, true);

		lkdtm_USERCOPY_STACK_FRAME_TO();

		break;

	case CT_USERCOPY_STACK_FRAME_FROM:

		do_usercopy_stack(false, true);

		lkdtm_USERCOPY_STACK_FRAME_FROM();

		break;

	case CT_USERCOPY_STACK_BEYOND:

		do_usercopy_stack(true, false);

		lkdtm_USERCOPY_STACK_BEYOND();

		break;

	case CT_USERCOPY_KERNEL:

		do_usercopy_kernel();

		lkdtm_USERCOPY_KERNEL();

		break;

	case CT_NONE:

	default:
@@ -1276,13 +1023,12 @@ static int __init lkdtm_module_init(void) 
	int n_debugfs_entries = 1; /* Assume only the direct entry */

	int i;



	/* Handle test-specific initialization. */

	lkdtm_usercopy_init();



	/* Make sure we can write to __ro_after_init values during __init */

	ro_after_init |= 0xAA;



	/* Prepare cache that lacks SLAB_USERCOPY flag. */

	bad_cache = kmem_cache_create("lkdtm-no-usercopy", cache_size, 0,

				      0, NULL);



	/* Register debugfs interface */

	lkdtm_debugfs_root = debugfs_create_dir("provoke-crash", NULL);

	if (!lkdtm_debugfs_root) {
@@ -1334,7 +1080,8 @@ static void __exit lkdtm_module_exit(void) 
{

	debugfs_remove_recursive(lkdtm_debugfs_root);



	kmem_cache_destroy(bad_cache);

	/* Handle test-specific clean-up. */

	lkdtm_usercopy_exit();



	unregister_jprobe(&lkdtm);

	pr_info("Crash point unregistered\n");

drivers/misc/lkdtm_usercopy.c

0 → 100644
+315 −0
Original line number Diff line number Diff line 
/*

 * This is for all the tests related to copy_to_user() and copy_from_user()

 * hardening.

 */

#define pr_fmt(fmt) "lkdtm: " fmt



#include <linux/kernel.h>

#include <linux/slab.h>

#include <linux/vmalloc.h>

#include <linux/mman.h>

#include <linux/uaccess.h>

#include <asm/cacheflush.h>



static size_t cache_size = 1024;

static struct kmem_cache *bad_cache;



static const unsigned char test_text[] = "This is a test.\n";



/*

 * Instead of adding -Wno-return-local-addr, just pass the stack address

 * through a function to obfuscate it from the compiler.

 */

static noinline unsigned char *trick_compiler(unsigned char *stack)

{

	return stack + 0;

}



static noinline unsigned char *do_usercopy_stack_callee(int value)

{

	unsigned char buf[32];

	int i;



	/* Exercise stack to avoid everything living in registers. */

	for (i = 0; i < sizeof(buf); i++) {

		buf[i] = value & 0xff;

	}



	return trick_compiler(buf);

}



static noinline void do_usercopy_stack(bool to_user, bool bad_frame)

{

	unsigned long user_addr;

	unsigned char good_stack[32];

	unsigned char *bad_stack;

	int i;



	/* Exercise stack to avoid everything living in registers. */

	for (i = 0; i < sizeof(good_stack); i++)

		good_stack[i] = test_text[i % sizeof(test_text)];



	/* This is a pointer to outside our current stack frame. */

	if (bad_frame) {

		bad_stack = do_usercopy_stack_callee((uintptr_t)bad_stack);

	} else {

		/* Put start address just inside stack. */

		bad_stack = task_stack_page(current) + THREAD_SIZE;

		bad_stack -= sizeof(unsigned long);

	}



	user_addr = vm_mmap(NULL, 0, PAGE_SIZE,

			    PROT_READ | PROT_WRITE | PROT_EXEC,

			    MAP_ANONYMOUS | MAP_PRIVATE, 0);

	if (user_addr >= TASK_SIZE) {

		pr_warn("Failed to allocate user memory\n");

		return;

	}



	if (to_user) {

		pr_info("attempting good copy_to_user of local stack\n");

		if (copy_to_user((void __user *)user_addr, good_stack,

				 sizeof(good_stack))) {

			pr_warn("copy_to_user failed unexpectedly?!\n");

			goto free_user;

		}



		pr_info("attempting bad copy_to_user of distant stack\n");

		if (copy_to_user((void __user *)user_addr, bad_stack,

				 sizeof(good_stack))) {

			pr_warn("copy_to_user failed, but lacked Oops\n");

			goto free_user;

		}

	} else {

		/*

		 * There isn't a safe way to not be protected by usercopy

		 * if we're going to write to another thread's stack.

		 */

		if (!bad_frame)

			goto free_user;



		pr_info("attempting good copy_from_user of local stack\n");

		if (copy_from_user(good_stack, (void __user *)user_addr,

				   sizeof(good_stack))) {

			pr_warn("copy_from_user failed unexpectedly?!\n");

			goto free_user;

		}



		pr_info("attempting bad copy_from_user of distant stack\n");

		if (copy_from_user(bad_stack, (void __user *)user_addr,

				   sizeof(good_stack))) {

			pr_warn("copy_from_user failed, but lacked Oops\n");

			goto free_user;

		}

	}



free_user:

	vm_munmap(user_addr, PAGE_SIZE);

}



static void do_usercopy_heap_size(bool to_user)

{

	unsigned long user_addr;

	unsigned char *one, *two;

	const size_t size = 1024;



	one = kmalloc(size, GFP_KERNEL);

	two = kmalloc(size, GFP_KERNEL);

	if (!one || !two) {

		pr_warn("Failed to allocate kernel memory\n");

		goto free_kernel;

	}



	user_addr = vm_mmap(NULL, 0, PAGE_SIZE,

			    PROT_READ | PROT_WRITE | PROT_EXEC,

			    MAP_ANONYMOUS | MAP_PRIVATE, 0);

	if (user_addr >= TASK_SIZE) {

		pr_warn("Failed to allocate user memory\n");

		goto free_kernel;

	}



	memset(one, 'A', size);

	memset(two, 'B', size);



	if (to_user) {

		pr_info("attempting good copy_to_user of correct size\n");

		if (copy_to_user((void __user *)user_addr, one, size)) {

			pr_warn("copy_to_user failed unexpectedly?!\n");

			goto free_user;

		}



		pr_info("attempting bad copy_to_user of too large size\n");

		if (copy_to_user((void __user *)user_addr, one, 2 * size)) {

			pr_warn("copy_to_user failed, but lacked Oops\n");

			goto free_user;

		}

	} else {

		pr_info("attempting good copy_from_user of correct size\n");

		if (copy_from_user(one, (void __user *)user_addr, size)) {

			pr_warn("copy_from_user failed unexpectedly?!\n");

			goto free_user;

		}



		pr_info("attempting bad copy_from_user of too large size\n");

		if (copy_from_user(one, (void __user *)user_addr, 2 * size)) {

			pr_warn("copy_from_user failed, but lacked Oops\n");

			goto free_user;

		}

	}



free_user:

	vm_munmap(user_addr, PAGE_SIZE);

free_kernel:

	kfree(one);

	kfree(two);

}



static void do_usercopy_heap_flag(bool to_user)

{

	unsigned long user_addr;

	unsigned char *good_buf = NULL;

	unsigned char *bad_buf = NULL;



	/* Make sure cache was prepared. */

	if (!bad_cache) {

		pr_warn("Failed to allocate kernel cache\n");

		return;

	}



	/*

	 * Allocate one buffer from each cache (kmalloc will have the

	 * SLAB_USERCOPY flag already, but "bad_cache" won't).

	 */

	good_buf = kmalloc(cache_size, GFP_KERNEL);

	bad_buf = kmem_cache_alloc(bad_cache, GFP_KERNEL);

	if (!good_buf || !bad_buf) {

		pr_warn("Failed to allocate buffers from caches\n");

		goto free_alloc;

	}



	/* Allocate user memory we'll poke at. */

	user_addr = vm_mmap(NULL, 0, PAGE_SIZE,

			    PROT_READ | PROT_WRITE | PROT_EXEC,

			    MAP_ANONYMOUS | MAP_PRIVATE, 0);

	if (user_addr >= TASK_SIZE) {

		pr_warn("Failed to allocate user memory\n");

		goto free_alloc;

	}



	memset(good_buf, 'A', cache_size);

	memset(bad_buf, 'B', cache_size);



	if (to_user) {

		pr_info("attempting good copy_to_user with SLAB_USERCOPY\n");

		if (copy_to_user((void __user *)user_addr, good_buf,

				 cache_size)) {

			pr_warn("copy_to_user failed unexpectedly?!\n");

			goto free_user;

		}



		pr_info("attempting bad copy_to_user w/o SLAB_USERCOPY\n");

		if (copy_to_user((void __user *)user_addr, bad_buf,

				 cache_size)) {

			pr_warn("copy_to_user failed, but lacked Oops\n");

			goto free_user;

		}

	} else {

		pr_info("attempting good copy_from_user with SLAB_USERCOPY\n");

		if (copy_from_user(good_buf, (void __user *)user_addr,

				   cache_size)) {

			pr_warn("copy_from_user failed unexpectedly?!\n");

			goto free_user;

		}



		pr_info("attempting bad copy_from_user w/o SLAB_USERCOPY\n");

		if (copy_from_user(bad_buf, (void __user *)user_addr,

				   cache_size)) {

			pr_warn("copy_from_user failed, but lacked Oops\n");

			goto free_user;

		}

	}



free_user:

	vm_munmap(user_addr, PAGE_SIZE);

free_alloc:

	if (bad_buf)

		kmem_cache_free(bad_cache, bad_buf);

	kfree(good_buf);

}



/* Callable tests. */

void lkdtm_USERCOPY_HEAP_SIZE_TO(void)

{

	do_usercopy_heap_size(true);

}



void lkdtm_USERCOPY_HEAP_SIZE_FROM(void)

{

	do_usercopy_heap_size(false);

}



void lkdtm_USERCOPY_HEAP_FLAG_TO(void)

{

	do_usercopy_heap_flag(true);

}



void lkdtm_USERCOPY_HEAP_FLAG_FROM(void)

{

	do_usercopy_heap_flag(false);

}



void lkdtm_USERCOPY_STACK_FRAME_TO(void)

{

	do_usercopy_stack(true, true);

}



void lkdtm_USERCOPY_STACK_FRAME_FROM(void)

{

	do_usercopy_stack(false, true);

}



void lkdtm_USERCOPY_STACK_BEYOND(void)

{

	do_usercopy_stack(true, false);

}



void lkdtm_USERCOPY_KERNEL(void)

{

	unsigned long user_addr;



	user_addr = vm_mmap(NULL, 0, PAGE_SIZE,

			    PROT_READ | PROT_WRITE | PROT_EXEC,

			    MAP_ANONYMOUS | MAP_PRIVATE, 0);

	if (user_addr >= TASK_SIZE) {

		pr_warn("Failed to allocate user memory\n");

		return;

	}



	pr_info("attempting good copy_to_user from kernel rodata\n");

	if (copy_to_user((void __user *)user_addr, test_text,

			 sizeof(test_text))) {

		pr_warn("copy_to_user failed unexpectedly?!\n");

		goto free_user;

	}



	pr_info("attempting bad copy_to_user from kernel text\n");

	if (copy_to_user((void __user *)user_addr, vm_mmap, PAGE_SIZE)) {

		pr_warn("copy_to_user failed, but lacked Oops\n");

		goto free_user;

	}



free_user:

	vm_munmap(user_addr, PAGE_SIZE);

}



void __init lkdtm_usercopy_init(void)

{

	/* Prepare cache that lacks SLAB_USERCOPY flag. */

	bad_cache = kmem_cache_create("lkdtm-no-usercopy", cache_size, 0,

				      0, NULL);

}



void __exit lkdtm_usercopy_exit(void)

{

	kmem_cache_destroy(bad_cache);

}