Commit cf6219ee authored by Kees Cook's avatar Kees Cook Committed by Shuah Khan
Browse files

usercopy: Convert test_user_copy to KUnit test 



Convert the runtime tests of hardened usercopy to standard KUnit tests.

Additionally disable usercopy_test_invalid() for systems with separate
address spaces (or no MMU) since it's not sensible to test for address
confusion there (e.g. m68k).

Co-developed-by: default avatarVitor Massaru Iha <vitor@massaru.org>
Signed-off-by: default avatarVitor Massaru Iha <vitor@massaru.org>
Link: https://lore.kernel.org/r/20200721174654.72132-1-vitor@massaru.org


Tested-by: default avatarIvan Orlov <ivan.orlov0322@gmail.com>
Reviewed-by: default avatarDavid Gow <davidgow@google.com>
Signed-off-by: default avatarKees Cook <kees@kernel.org>
Signed-off-by: default avatarShuah Khan <skhan@linuxfoundation.org>
parent 51104c19

MAINTAINERS

+1 −0
Original line number Diff line number Diff line
@@ -11962,6 +11962,7 @@ F: arch/*/configs/hardening.config 
F:	include/linux/overflow.h

F:	include/linux/randomize_kstack.h

F:	kernel/configs/hardening.config

F:	lib/usercopy_kunit.c

F:	mm/usercopy.c

K:	\b(add|choose)_random_kstack_offset\b

K:	\b__check_(object_size|heap_object)\b

lib/Kconfig.debug

+9 −12
Original line number Diff line number Diff line
@@ -2505,18 +2505,6 @@ config TEST_VMALLOC 


	  If unsure, say N.



config TEST_USER_COPY

	tristate "Test user/kernel boundary protections"

	depends on m

	help

	  This builds the "test_user_copy" module that runs sanity checks

	  on the copy_to/from_user infrastructure, making sure basic

	  user/kernel boundary testing is working. If it fails to load,

	  a regression has been detected in the user/kernel memory boundary

	  protections.



	  If unsure, say N.



config TEST_BPF

	tristate "Test BPF filter functionality"

	depends on m && NET
@@ -2814,6 +2802,15 @@ config SIPHASH_KUNIT_TEST 
	  This is intended to help people writing architecture-specific

	  optimized versions.  If unsure, say N.



config USERCOPY_KUNIT_TEST

	tristate "KUnit Test for user/kernel boundary protections"

	depends on KUNIT

	default KUNIT_ALL_TESTS

	help

	  This builds the "usercopy_kunit" module that runs sanity checks

	  on the copy_to/from_user infrastructure, making sure basic

	  user/kernel boundary testing is working.



config TEST_UDELAY

	tristate "udelay test driver"

	help

lib/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -78,7 +78,6 @@ obj-$(CONFIG_TEST_LKM) += test_module.o 
obj-$(CONFIG_TEST_VMALLOC) += test_vmalloc.o

obj-$(CONFIG_TEST_RHASHTABLE) += test_rhashtable.o

obj-$(CONFIG_TEST_SORT) += test_sort.o

obj-$(CONFIG_TEST_USER_COPY) += test_user_copy.o

obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_keys.o

obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_key_base.o

obj-$(CONFIG_TEST_DYNAMIC_DEBUG) += test_dynamic_debug.o
@@ -388,6 +387,7 @@ CFLAGS_fortify_kunit.o += $(call cc-disable-warning, stringop-truncation) 
CFLAGS_fortify_kunit.o += $(DISABLE_STRUCTLEAK_PLUGIN)

obj-$(CONFIG_FORTIFY_KUNIT_TEST) += fortify_kunit.o

obj-$(CONFIG_SIPHASH_KUNIT_TEST) += siphash_kunit.o

obj-$(CONFIG_USERCOPY_KUNIT_TEST) += usercopy_kunit.o



obj-$(CONFIG_GENERIC_LIB_DEVMEM_IS_ALLOWED) += devmem_is_allowed.o

lib/test_user_copy.c→lib/usercopy_kunit.c

+329 −0
Original line number Diff line number Diff line
@@ -15,7 +15,7 @@ 
#include <linux/sched.h>

#include <linux/slab.h>

#include <linux/uaccess.h>

#include <linux/vmalloc.h>

#include <kunit/test.h>



/*

 * Several 32-bit architectures support 64-bit {get,put}_user() calls.
@@ -31,26 +31,27 @@ 
# define TEST_U64

#endif



#define test(condition, msg, ...)					\

({									\

	int cond = (condition);						\

	if (cond)							\

		pr_warn("[%d] " msg "\n", __LINE__, ##__VA_ARGS__);	\

	cond;								\

})

struct usercopy_test_priv {

	char *kmem;

	char __user *umem;

	size_t size;

};



static bool is_zeroed(void *from, size_t size)

{

	return memchr_inv(from, 0x0, size) == NULL;

}



static int test_check_nonzero_user(char *kmem, char __user *umem, size_t size)

/* Test usage of check_nonzero_user(). */

static void usercopy_test_check_nonzero_user(struct kunit *test)

{

	int ret = 0;

	size_t start, end, i, zero_start, zero_end;

	struct usercopy_test_priv *priv = test->priv;

	char __user *umem = priv->umem;

	char *kmem = priv->kmem;

	size_t size = priv->size;



	if (test(size < 2 * PAGE_SIZE, "buffer too small"))

		return -EINVAL;

	KUNIT_ASSERT_GE_MSG(test, size, 2 * PAGE_SIZE, "buffer too small");



	/*

	 * We want to cross a page boundary to exercise the code more
@@ -84,7 +85,7 @@ static int test_check_nonzero_user(char *kmem, char __user *umem, size_t size) 
	for (i = zero_end; i < size; i += 2)

		kmem[i] = 0xff;



	ret |= test(copy_to_user(umem, kmem, size),

	KUNIT_EXPECT_EQ_MSG(test, copy_to_user(umem, kmem, size), 0,

		"legitimate copy_to_user failed");



	for (start = 0; start <= size; start++) {
@@ -93,35 +94,32 @@ static int test_check_nonzero_user(char *kmem, char __user *umem, size_t size) 
			int retval = check_zeroed_user(umem + start, len);

			int expected = is_zeroed(kmem + start, len);



			ret |= test(retval != expected,

			KUNIT_ASSERT_EQ_MSG(test, retval, expected,

				"check_nonzero_user(=%d) != memchr_inv(=%d) mismatch (start=%zu, end=%zu)",

				retval, expected, start, end);

		}

	}



	return ret;

}



static int test_copy_struct_from_user(char *kmem, char __user *umem,

				      size_t size)

/* Test usage of copy_struct_from_user(). */

static void usercopy_test_copy_struct_from_user(struct kunit *test)

{

	int ret = 0;

	char *umem_src = NULL, *expected = NULL;

	struct usercopy_test_priv *priv = test->priv;

	char __user *umem = priv->umem;

	char *kmem = priv->kmem;

	size_t size = priv->size;

	size_t ksize, usize;



	umem_src = kmalloc(size, GFP_KERNEL);

	ret = test(umem_src == NULL, "kmalloc failed");

	if (ret)

		goto out_free;

	umem_src = kunit_kmalloc(test, size, GFP_KERNEL);

	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, umem_src);



	expected = kmalloc(size, GFP_KERNEL);

	ret = test(expected == NULL, "kmalloc failed");

	if (ret)

		goto out_free;

	expected = kunit_kmalloc(test, size, GFP_KERNEL);

	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, expected);



	/* Fill umem with a fixed byte pattern. */

	memset(umem_src, 0x3e, size);

	ret |= test(copy_to_user(umem, umem_src, size),

	KUNIT_ASSERT_EQ_MSG(test, copy_to_user(umem, umem_src, size), 0,

		    "legitimate copy_to_user failed");



	/* Check basic case -- (usize == ksize). */
@@ -131,9 +129,9 @@ static int test_copy_struct_from_user(char *kmem, char __user *umem, 
	memcpy(expected, umem_src, ksize);



	memset(kmem, 0x0, size);

	ret |= test(copy_struct_from_user(kmem, ksize, umem, usize),

	KUNIT_EXPECT_EQ_MSG(test, copy_struct_from_user(kmem, ksize, umem, usize), 0,

		    "copy_struct_from_user(usize == ksize) failed");

	ret |= test(memcmp(kmem, expected, ksize),

	KUNIT_EXPECT_MEMEQ_MSG(test, kmem, expected, ksize,

		    "copy_struct_from_user(usize == ksize) gives unexpected copy");



	/* Old userspace case -- (usize < ksize). */
@@ -144,9 +142,9 @@ static int test_copy_struct_from_user(char *kmem, char __user *umem, 
	memset(expected + usize, 0x0, ksize - usize);



	memset(kmem, 0x0, size);

	ret |= test(copy_struct_from_user(kmem, ksize, umem, usize),

	KUNIT_EXPECT_EQ_MSG(test, copy_struct_from_user(kmem, ksize, umem, usize), 0,

		    "copy_struct_from_user(usize < ksize) failed");

	ret |= test(memcmp(kmem, expected, ksize),

	KUNIT_EXPECT_MEMEQ_MSG(test, kmem, expected, ksize,

		    "copy_struct_from_user(usize < ksize) gives unexpected copy");



	/* New userspace (-E2BIG) case -- (usize > ksize). */
@@ -154,7 +152,7 @@ static int test_copy_struct_from_user(char *kmem, char __user *umem, 
	usize = size;



	memset(kmem, 0x0, size);

	ret |= test(copy_struct_from_user(kmem, ksize, umem, usize) != -E2BIG,

	KUNIT_EXPECT_EQ_MSG(test, copy_struct_from_user(kmem, ksize, umem, usize), -E2BIG,

		    "copy_struct_from_user(usize > ksize) didn't give E2BIG");



	/* New userspace (success) case -- (usize > ksize). */
@@ -162,78 +160,46 @@ static int test_copy_struct_from_user(char *kmem, char __user *umem, 
	usize = size;



	memcpy(expected, umem_src, ksize);

	ret |= test(clear_user(umem + ksize, usize - ksize),

	KUNIT_EXPECT_EQ_MSG(test, clear_user(umem + ksize, usize - ksize), 0,

		    "legitimate clear_user failed");



	memset(kmem, 0x0, size);

	ret |= test(copy_struct_from_user(kmem, ksize, umem, usize),

	KUNIT_EXPECT_EQ_MSG(test, copy_struct_from_user(kmem, ksize, umem, usize), 0,

		    "copy_struct_from_user(usize > ksize) failed");

	ret |= test(memcmp(kmem, expected, ksize),

	KUNIT_EXPECT_MEMEQ_MSG(test, kmem, expected, ksize,

		    "copy_struct_from_user(usize > ksize) gives unexpected copy");



out_free:

	kfree(expected);

	kfree(umem_src);

	return ret;

}



static int __init test_user_copy_init(void)

{

	int ret = 0;

	char *kmem;

	char __user *usermem;

	char *bad_usermem;

	unsigned long user_addr;

	u8 val_u8;

	u16 val_u16;

	u32 val_u32;

#ifdef TEST_U64

	u64 val_u64;

#endif



	kmem = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);

	if (!kmem)

		return -ENOMEM;



	user_addr = vm_mmap(NULL, 0, PAGE_SIZE * 2,

			    PROT_READ | PROT_WRITE | PROT_EXEC,

			    MAP_ANONYMOUS | MAP_PRIVATE, 0);

	if (user_addr >= (unsigned long)(TASK_SIZE)) {

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

		kfree(kmem);

		return -ENOMEM;

	}



	usermem = (char __user *)user_addr;

	bad_usermem = (char *)user_addr;



/*

 * Legitimate usage: none of these copies should fail.

 */

static void usercopy_test_valid(struct kunit *test)

{

	struct usercopy_test_priv *priv = test->priv;

	char __user *usermem = priv->umem;

	char *kmem = priv->kmem;



	memset(kmem, 0x3a, PAGE_SIZE * 2);

	ret |= test(copy_to_user(usermem, kmem, PAGE_SIZE),

	KUNIT_EXPECT_EQ_MSG(test, 0, copy_to_user(usermem, kmem, PAGE_SIZE),

	     "legitimate copy_to_user failed");

	memset(kmem, 0x0, PAGE_SIZE);

	ret |= test(copy_from_user(kmem, usermem, PAGE_SIZE),

	KUNIT_EXPECT_EQ_MSG(test, 0, copy_from_user(kmem, usermem, PAGE_SIZE),

	     "legitimate copy_from_user failed");

	ret |= test(memcmp(kmem, kmem + PAGE_SIZE, PAGE_SIZE),

	KUNIT_EXPECT_MEMEQ_MSG(test, kmem, kmem + PAGE_SIZE, PAGE_SIZE,

	     "legitimate usercopy failed to copy data");



#define test_legit(size, check)						\

	do {								\

		val_##size = check;					  \

		ret |= test(put_user(val_##size, (size __user *)usermem), \

		size val_##size = (check);				\

		KUNIT_EXPECT_EQ_MSG(test, 0,				\

			put_user(val_##size, (size __user *)usermem),	\

			"legitimate put_user (" #size ") failed");	\

		val_##size = 0;						\

		ret |= test(get_user(val_##size, (size __user *)usermem), \

		KUNIT_EXPECT_EQ_MSG(test, 0,				\

			get_user(val_##size, (size __user *)usermem),	\

			"legitimate get_user (" #size ") failed");	\

		ret |= test(val_##size != check,			  \

		KUNIT_EXPECT_EQ_MSG(test, val_##size, check,		\

			"legitimate get_user (" #size ") failed to do copy"); \

		if (val_##size != check) {				  \

			pr_info("0x%llx != 0x%llx\n",			  \

				(unsigned long long)val_##size,		  \

				(unsigned long long)check);		  \

		}							  \

	} while (0)



	test_legit(u8,  0x5a);
@@ -243,27 +209,36 @@ static int __init test_user_copy_init(void) 
	test_legit(u64, 0x5a5b5c5d6a6b6c6d);

#endif

#undef test_legit



	/* Test usage of check_nonzero_user(). */

	ret |= test_check_nonzero_user(kmem, usermem, 2 * PAGE_SIZE);

	/* Test usage of copy_struct_from_user(). */

	ret |= test_copy_struct_from_user(kmem, usermem, 2 * PAGE_SIZE);

}



/*

 * Invalid usage: none of these copies should succeed.

 */

static void usercopy_test_invalid(struct kunit *test)

{

	struct usercopy_test_priv *priv = test->priv;

	char __user *usermem = priv->umem;

	char *bad_usermem = (char *)usermem;

	char *kmem = priv->kmem;

	u64 *kmem_u64 = (u64 *)kmem;



	if (IS_ENABLED(CONFIG_ALTERNATE_USER_ADDRESS_SPACE) ||

	    !IS_ENABLED(CONFIG_MMU)) {

		kunit_skip(test, "Testing for kernel/userspace address confusion is only sensible on architectures with a shared address space");

		return;

	}



	/* Prepare kernel memory with check values. */

	memset(kmem, 0x5a, PAGE_SIZE);

	memset(kmem + PAGE_SIZE, 0, PAGE_SIZE);



	/* Reject kernel-to-kernel copies through copy_from_user(). */

	ret |= test(!copy_from_user(kmem, (char __user *)(kmem + PAGE_SIZE),

				    PAGE_SIZE),

	KUNIT_EXPECT_NE_MSG(test, copy_from_user(kmem, (char __user *)(kmem + PAGE_SIZE),

						 PAGE_SIZE), 0,

		    "illegal all-kernel copy_from_user passed");



	/* Destination half of buffer should have been zeroed. */

	ret |= test(memcmp(kmem + PAGE_SIZE, kmem, PAGE_SIZE),

	KUNIT_EXPECT_MEMEQ_MSG(test, kmem + PAGE_SIZE, kmem, PAGE_SIZE,

		    "zeroing failure for illegal all-kernel copy_from_user");



#if 0
@@ -273,30 +248,32 @@ static int __init test_user_copy_init(void) 
	 * to be tested in LKDTM instead, since this test module does not

	 * expect to explode.

	 */

	ret |= test(!copy_from_user(bad_usermem, (char __user *)kmem,

				    PAGE_SIZE),

	KUNIT_EXPECT_NE_MSG(test, copy_from_user(bad_usermem, (char __user *)kmem,

						 PAGE_SIZE), 0,

		    "illegal reversed copy_from_user passed");

#endif

	ret |= test(!copy_to_user((char __user *)kmem, kmem + PAGE_SIZE,

				  PAGE_SIZE),

	KUNIT_EXPECT_NE_MSG(test, copy_to_user((char __user *)kmem, kmem + PAGE_SIZE,

					       PAGE_SIZE), 0,

		    "illegal all-kernel copy_to_user passed");

	ret |= test(!copy_to_user((char __user *)kmem, bad_usermem,

				  PAGE_SIZE),



	KUNIT_EXPECT_NE_MSG(test, copy_to_user((char __user *)kmem, bad_usermem,

					       PAGE_SIZE), 0,

		    "illegal reversed copy_to_user passed");



#define test_illegal(size, check)							\

	do {										\

		val_##size = (check);					    \

		ret |= test(!get_user(val_##size, (size __user *)kmem),	    \

		size val_##size = (check);						\

		/* get_user() */							\

		KUNIT_EXPECT_NE_MSG(test, get_user(val_##size, (size __user *)kmem), 0,	\

		    "illegal get_user (" #size ") passed");				\

		ret |= test(val_##size != (size)0,			    \

		KUNIT_EXPECT_EQ_MSG(test, val_##size, 0,				\

		    "zeroing failure for illegal get_user (" #size ")");		\

		if (val_##size != (size)0) {				    \

			pr_info("0x%llx != 0\n",			    \

				(unsigned long long)val_##size);	    \

		}							    \

		ret |= test(!put_user(val_##size, (size __user *)kmem),	    \

		/* put_user() */							\

		*kmem_u64 = 0xF09FA4AFF09FA4AF;						\

		KUNIT_EXPECT_NE_MSG(test, put_user(val_##size, (size __user *)kmem), 0,	\

		    "illegal put_user (" #size ") passed");				\

		KUNIT_EXPECT_EQ_MSG(test, *kmem_u64, 0xF09FA4AFF09FA4AF,		\

		    "illegal put_user (" #size ") wrote to kernel memory!");		\

	} while (0)



	test_illegal(u8,  0x5a);
@@ -306,26 +283,47 @@ static int __init test_user_copy_init(void) 
	test_illegal(u64, 0x5a5b5c5d6a6b6c6d);

#endif

#undef test_illegal

}



	vm_munmap(user_addr, PAGE_SIZE * 2);

	kfree(kmem);

static int usercopy_test_init(struct kunit *test)

{

	struct usercopy_test_priv *priv;

	unsigned long user_addr;



	if (ret == 0) {

		pr_info("tests passed.\n");

		return 0;

	}

	priv = kunit_kzalloc(test, sizeof(*priv), GFP_KERNEL);

	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, priv);

	test->priv = priv;

	priv->size = PAGE_SIZE * 2;



	return -EINVAL;

}

	priv->kmem = kunit_kmalloc(test, priv->size, GFP_KERNEL);

	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, priv->kmem);



module_init(test_user_copy_init);

	user_addr = kunit_vm_mmap(test, NULL, 0, priv->size,

			    PROT_READ | PROT_WRITE | PROT_EXEC,

			    MAP_ANONYMOUS | MAP_PRIVATE, 0);

	KUNIT_ASSERT_NE_MSG(test, user_addr, 0,

		"Could not create userspace mm");

	KUNIT_ASSERT_LT_MSG(test, user_addr, (unsigned long)TASK_SIZE,

		"Failed to allocate user memory");

	priv->umem = (char __user *)user_addr;



static void __exit test_user_copy_exit(void)

{

	pr_info("unloaded.\n");

	return 0;

}



module_exit(test_user_copy_exit);



MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");

static struct kunit_case usercopy_test_cases[] = {

	KUNIT_CASE(usercopy_test_valid),

	KUNIT_CASE(usercopy_test_invalid),

	KUNIT_CASE(usercopy_test_check_nonzero_user),

	KUNIT_CASE(usercopy_test_copy_struct_from_user),

	{}

};



static struct kunit_suite usercopy_test_suite = {

	.name = "usercopy",

	.init = usercopy_test_init,

	.test_cases = usercopy_test_cases,

};



kunit_test_suites(&usercopy_test_suite);

MODULE_AUTHOR("Kees Cook <kees@kernel.org>");

MODULE_LICENSE("GPL");