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: Vitor Massaru Iha <vitor@massaru.org>
Signed-off-by: Vitor Massaru Iha <vitor@massaru.org>
Link: https://lore.kernel.org/r/20200721174654.72132-1-vitor@massaru.org
Tested-by: Ivan Orlov <ivan.orlov0322@gmail.com>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Kees Cook <kees@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

5 files changed, 340 insertions, 344 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index d6c90161c7bf..9a4883f78853 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -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
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 59b6765d86b8..561e346f5cb0 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -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
diff --git a/lib/Makefile b/lib/Makefile
index 3b1769045651..fae5cc67b95a 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -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
 
diff --git a/lib/test_user_copy.c b/lib/test_user_copy.c
deleted file mode 100644
index 5ff04d8fe971..000000000000
--- a/lib/test_user_copy.c
+++ /dev/null
@@ -1,331 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * Kernel module for testing copy_to/from_user infrastructure.
- *
- * Copyright 2013 Google Inc. All Rights Reserved
- *
- * Authors:
- *      Kees Cook       <keescook@chromium.org>
- */
-
-#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
-
-#include <linux/mman.h>
-#include <linux/module.h>
-#include <linux/sched.h>
-#include <linux/slab.h>
-#include <linux/uaccess.h>
-#include <linux/vmalloc.h>
-
-/*
- * Several 32-bit architectures support 64-bit {get,put}_user() calls.
- * As there doesn't appear to be anything that can safely determine
- * their capability at compile-time, we just have to opt-out certain archs.
- */
-#if BITS_PER_LONG == 64 || (!(defined(CONFIG_ARM) && !defined(MMU)) && \
-			    !defined(CONFIG_M68K) &&		\
-			    !defined(CONFIG_MICROBLAZE) &&	\
-			    !defined(CONFIG_NIOS2) &&		\
-			    !defined(CONFIG_PPC32) &&		\
-			    !defined(CONFIG_SUPERH))
-# define TEST_U64
-#endif
-
-#define test(condition, msg, ...)					\
-({									\
-	int cond = (condition);						\
-	if (cond)							\
-		pr_warn("[%d] " msg "\n", __LINE__, ##__VA_ARGS__);	\
-	cond;								\
-})
-
-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)
-{
-	int ret = 0;
-	size_t start, end, i, zero_start, zero_end;
-
-	if (test(size < 2 * PAGE_SIZE, "buffer too small"))
-		return -EINVAL;
-
-	/*
-	 * We want to cross a page boundary to exercise the code more
-	 * effectively. We also don't want to make the size we scan too large,
-	 * otherwise the test can take a long time and cause soft lockups. So
-	 * scan a 1024 byte region across the page boundary.
-	 */
-	size = 1024;
-	start = PAGE_SIZE - (size / 2);
-
-	kmem += start;
-	umem += start;
-
-	zero_start = size / 4;
-	zero_end = size - zero_start;
-
-	/*
-	 * We conduct a series of check_nonzero_user() tests on a block of
-	 * memory with the following byte-pattern (trying every possible
-	 * [start,end] pair):
-	 *
-	 *   [ 00 ff 00 ff ... 00 00 00 00 ... ff 00 ff 00 ]
-	 *
-	 * And we verify that check_nonzero_user() acts identically to
-	 * memchr_inv().
-	 */
-
-	memset(kmem, 0x0, size);
-	for (i = 1; i < zero_start; i += 2)
-		kmem[i] = 0xff;
-	for (i = zero_end; i < size; i += 2)
-		kmem[i] = 0xff;
-
-	ret |= test(copy_to_user(umem, kmem, size),
-		    "legitimate copy_to_user failed");
-
-	for (start = 0; start <= size; start++) {
-		for (end = start; end <= size; end++) {
-			size_t len = end - start;
-			int retval = check_zeroed_user(umem + start, len);
-			int expected = is_zeroed(kmem + start, len);
-
-			ret |= 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)
-{
-	int ret = 0;
-	char *umem_src = NULL, *expected = NULL;
-	size_t ksize, usize;
-
-	umem_src = kmalloc(size, GFP_KERNEL);
-	ret = test(umem_src == NULL, "kmalloc failed");
-	if (ret)
-		goto out_free;
-
-	expected = kmalloc(size, GFP_KERNEL);
-	ret = test(expected == NULL, "kmalloc failed");
-	if (ret)
-		goto out_free;
-
-	/* Fill umem with a fixed byte pattern. */
-	memset(umem_src, 0x3e, size);
-	ret |= test(copy_to_user(umem, umem_src, size),
-		    "legitimate copy_to_user failed");
-
-	/* Check basic case -- (usize == ksize). */
-	ksize = size;
-	usize = size;
-
-	memcpy(expected, umem_src, ksize);
-
-	memset(kmem, 0x0, size);
-	ret |= test(copy_struct_from_user(kmem, ksize, umem, usize),
-		    "copy_struct_from_user(usize == ksize) failed");
-	ret |= test(memcmp(kmem, expected, ksize),
-		    "copy_struct_from_user(usize == ksize) gives unexpected copy");
-
-	/* Old userspace case -- (usize < ksize). */
-	ksize = size;
-	usize = size / 2;
-
-	memcpy(expected, umem_src, usize);
-	memset(expected + usize, 0x0, ksize - usize);
-
-	memset(kmem, 0x0, size);
-	ret |= test(copy_struct_from_user(kmem, ksize, umem, usize),
-		    "copy_struct_from_user(usize < ksize) failed");
-	ret |= test(memcmp(kmem, expected, ksize),
-		    "copy_struct_from_user(usize < ksize) gives unexpected copy");
-
-	/* New userspace (-E2BIG) case -- (usize > ksize). */
-	ksize = size / 2;
-	usize = size;
-
-	memset(kmem, 0x0, size);
-	ret |= 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). */
-	ksize = size / 2;
-	usize = size;
-
-	memcpy(expected, umem_src, ksize);
-	ret |= test(clear_user(umem + ksize, usize - ksize),
-		    "legitimate clear_user failed");
-
-	memset(kmem, 0x0, size);
-	ret |= test(copy_struct_from_user(kmem, ksize, umem, usize),
-		    "copy_struct_from_user(usize > ksize) failed");
-	ret |= test(memcmp(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.
-	 */
-	memset(kmem, 0x3a, PAGE_SIZE * 2);
-	ret |= test(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),
-		    "legitimate copy_from_user failed");
-	ret |= test(memcmp(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), \
-		    "legitimate put_user (" #size ") failed");		  \
-		val_##size = 0;						  \
-		ret |= test(get_user(val_##size, (size __user *)usermem), \
-		    "legitimate get_user (" #size ") failed");		  \
-		ret |= 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);
-	test_legit(u16, 0x5a5b);
-	test_legit(u32, 0x5a5b5c5d);
-#ifdef TEST_U64
-	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.
-	 */
-
-	/* 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),
-		    "illegal all-kernel copy_from_user passed");
-
-	/* Destination half of buffer should have been zeroed. */
-	ret |= test(memcmp(kmem + PAGE_SIZE, kmem, PAGE_SIZE),
-		    "zeroing failure for illegal all-kernel copy_from_user");
-
-#if 0
-	/*
-	 * When running with SMAP/PAN/etc, this will Oops the kernel
-	 * due to the zeroing of userspace memory on failure. This needs
-	 * 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),
-		    "illegal reversed copy_from_user passed");
-#endif
-	ret |= test(!copy_to_user((char __user *)kmem, kmem + PAGE_SIZE,
-				  PAGE_SIZE),
-		    "illegal all-kernel copy_to_user passed");
-	ret |= test(!copy_to_user((char __user *)kmem, bad_usermem,
-				  PAGE_SIZE),
-		    "illegal reversed copy_to_user passed");
-
-#define test_illegal(size, check)					    \
-	do {								    \
-		val_##size = (check);					    \
-		ret |= test(!get_user(val_##size, (size __user *)kmem),	    \
-		    "illegal get_user (" #size ") passed");		    \
-		ret |= test(val_##size != (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),	    \
-		    "illegal put_user (" #size ") passed");		    \
-	} while (0)
-
-	test_illegal(u8,  0x5a);
-	test_illegal(u16, 0x5a5b);
-	test_illegal(u32, 0x5a5b5c5d);
-#ifdef TEST_U64
-	test_illegal(u64, 0x5a5b5c5d6a6b6c6d);
-#endif
-#undef test_illegal
-
-	vm_munmap(user_addr, PAGE_SIZE * 2);
-	kfree(kmem);
-
-	if (ret == 0) {
-		pr_info("tests passed.\n");
-		return 0;
-	}
-
-	return -EINVAL;
-}
-
-module_init(test_user_copy_init);
-
-static void __exit test_user_copy_exit(void)
-{
-	pr_info("unloaded.\n");
-}
-
-module_exit(test_user_copy_exit);
-
-MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
-MODULE_LICENSE("GPL");
diff --git a/lib/usercopy_kunit.c b/lib/usercopy_kunit.c
new file mode 100644
index 000000000000..45f1e558c464
--- /dev/null
+++ b/lib/usercopy_kunit.c
@@ -0,0 +1,329 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Kernel module for testing copy_to/from_user infrastructure.
+ *
+ * Copyright 2013 Google Inc. All Rights Reserved
+ *
+ * Authors:
+ *      Kees Cook       <keescook@chromium.org>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/mman.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <kunit/test.h>
+
+/*
+ * Several 32-bit architectures support 64-bit {get,put}_user() calls.
+ * As there doesn't appear to be anything that can safely determine
+ * their capability at compile-time, we just have to opt-out certain archs.
+ */
+#if BITS_PER_LONG == 64 || (!(defined(CONFIG_ARM) && !defined(MMU)) && \
+			    !defined(CONFIG_M68K) &&		\
+			    !defined(CONFIG_MICROBLAZE) &&	\
+			    !defined(CONFIG_NIOS2) &&		\
+			    !defined(CONFIG_PPC32) &&		\
+			    !defined(CONFIG_SUPERH))
+# define TEST_U64
+#endif
+
+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;
+}
+
+/* Test usage of check_nonzero_user(). */
+static void usercopy_test_check_nonzero_user(struct kunit *test)
+{
+	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;
+
+	KUNIT_ASSERT_GE_MSG(test, size, 2 * PAGE_SIZE, "buffer too small");
+
+	/*
+	 * We want to cross a page boundary to exercise the code more
+	 * effectively. We also don't want to make the size we scan too large,
+	 * otherwise the test can take a long time and cause soft lockups. So
+	 * scan a 1024 byte region across the page boundary.
+	 */
+	size = 1024;
+	start = PAGE_SIZE - (size / 2);
+
+	kmem += start;
+	umem += start;
+
+	zero_start = size / 4;
+	zero_end = size - zero_start;
+
+	/*
+	 * We conduct a series of check_nonzero_user() tests on a block of
+	 * memory with the following byte-pattern (trying every possible
+	 * [start,end] pair):
+	 *
+	 *   [ 00 ff 00 ff ... 00 00 00 00 ... ff 00 ff 00 ]
+	 *
+	 * And we verify that check_nonzero_user() acts identically to
+	 * memchr_inv().
+	 */
+
+	memset(kmem, 0x0, size);
+	for (i = 1; i < zero_start; i += 2)
+		kmem[i] = 0xff;
+	for (i = zero_end; i < size; i += 2)
+		kmem[i] = 0xff;
+
+	KUNIT_EXPECT_EQ_MSG(test, copy_to_user(umem, kmem, size), 0,
+		"legitimate copy_to_user failed");
+
+	for (start = 0; start <= size; start++) {
+		for (end = start; end <= size; end++) {
+			size_t len = end - start;
+			int retval = check_zeroed_user(umem + start, len);
+			int expected = is_zeroed(kmem + start, len);
+
+			KUNIT_ASSERT_EQ_MSG(test, retval, expected,
+				"check_nonzero_user(=%d) != memchr_inv(=%d) mismatch (start=%zu, end=%zu)",
+				retval, expected, start, end);
+		}
+	}
+}
+
+/* Test usage of copy_struct_from_user(). */
+static void usercopy_test_copy_struct_from_user(struct kunit *test)
+{
+	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 = kunit_kmalloc(test, size, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, umem_src);
+
+	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);
+	KUNIT_ASSERT_EQ_MSG(test, copy_to_user(umem, umem_src, size), 0,
+		    "legitimate copy_to_user failed");
+
+	/* Check basic case -- (usize == ksize). */
+	ksize = size;
+	usize = size;
+
+	memcpy(expected, umem_src, ksize);
+
+	memset(kmem, 0x0, size);
+	KUNIT_EXPECT_EQ_MSG(test, copy_struct_from_user(kmem, ksize, umem, usize), 0,
+		    "copy_struct_from_user(usize == ksize) failed");
+	KUNIT_EXPECT_MEMEQ_MSG(test, kmem, expected, ksize,
+		    "copy_struct_from_user(usize == ksize) gives unexpected copy");
+
+	/* Old userspace case -- (usize < ksize). */
+	ksize = size;
+	usize = size / 2;
+
+	memcpy(expected, umem_src, usize);
+	memset(expected + usize, 0x0, ksize - usize);
+
+	memset(kmem, 0x0, size);
+	KUNIT_EXPECT_EQ_MSG(test, copy_struct_from_user(kmem, ksize, umem, usize), 0,
+		    "copy_struct_from_user(usize < ksize) failed");
+	KUNIT_EXPECT_MEMEQ_MSG(test, kmem, expected, ksize,
+		    "copy_struct_from_user(usize < ksize) gives unexpected copy");
+
+	/* New userspace (-E2BIG) case -- (usize > ksize). */
+	ksize = size / 2;
+	usize = size;
+
+	memset(kmem, 0x0, size);
+	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). */
+	ksize = size / 2;
+	usize = size;
+
+	memcpy(expected, umem_src, ksize);
+	KUNIT_EXPECT_EQ_MSG(test, clear_user(umem + ksize, usize - ksize), 0,
+		    "legitimate clear_user failed");
+
+	memset(kmem, 0x0, size);
+	KUNIT_EXPECT_EQ_MSG(test, copy_struct_from_user(kmem, ksize, umem, usize), 0,
+		    "copy_struct_from_user(usize > ksize) failed");
+	KUNIT_EXPECT_MEMEQ_MSG(test, kmem, expected, ksize,
+		    "copy_struct_from_user(usize > ksize) gives unexpected copy");
+}
+
+/*
+ * 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);
+	KUNIT_EXPECT_EQ_MSG(test, 0, copy_to_user(usermem, kmem, PAGE_SIZE),
+	     "legitimate copy_to_user failed");
+	memset(kmem, 0x0, PAGE_SIZE);
+	KUNIT_EXPECT_EQ_MSG(test, 0, copy_from_user(kmem, usermem, PAGE_SIZE),
+	     "legitimate copy_from_user failed");
+	KUNIT_EXPECT_MEMEQ_MSG(test, kmem, kmem + PAGE_SIZE, PAGE_SIZE,
+	     "legitimate usercopy failed to copy data");
+
+#define test_legit(size, check)						\
+	do {								\
+		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;						\
+		KUNIT_EXPECT_EQ_MSG(test, 0,				\
+			get_user(val_##size, (size __user *)usermem),	\
+			"legitimate get_user (" #size ") failed");	\
+		KUNIT_EXPECT_EQ_MSG(test, val_##size, check,		\
+			"legitimate get_user (" #size ") failed to do copy"); \
+	} while (0)
+
+	test_legit(u8,  0x5a);
+	test_legit(u16, 0x5a5b);
+	test_legit(u32, 0x5a5b5c5d);
+#ifdef TEST_U64
+	test_legit(u64, 0x5a5b5c5d6a6b6c6d);
+#endif
+#undef test_legit
+}
+
+/*
+ * 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(). */
+	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. */
+	KUNIT_EXPECT_MEMEQ_MSG(test, kmem + PAGE_SIZE, kmem, PAGE_SIZE,
+		    "zeroing failure for illegal all-kernel copy_from_user");
+
+#if 0
+	/*
+	 * When running with SMAP/PAN/etc, this will Oops the kernel
+	 * due to the zeroing of userspace memory on failure. This needs
+	 * to be tested in LKDTM instead, since this test module does not
+	 * expect to explode.
+	 */
+	KUNIT_EXPECT_NE_MSG(test, copy_from_user(bad_usermem, (char __user *)kmem,
+						 PAGE_SIZE), 0,
+		    "illegal reversed copy_from_user passed");
+#endif
+	KUNIT_EXPECT_NE_MSG(test, copy_to_user((char __user *)kmem, kmem + PAGE_SIZE,
+					       PAGE_SIZE), 0,
+		    "illegal all-kernel copy_to_user passed");
+
+	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 {										\
+		size val_##size = (check);						\
+		/* get_user() */							\
+		KUNIT_EXPECT_NE_MSG(test, get_user(val_##size, (size __user *)kmem), 0,	\
+		    "illegal get_user (" #size ") passed");				\
+		KUNIT_EXPECT_EQ_MSG(test, val_##size, 0,				\
+		    "zeroing failure for illegal get_user (" #size ")");		\
+		/* 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);
+	test_illegal(u16, 0x5a5b);
+	test_illegal(u32, 0x5a5b5c5d);
+#ifdef TEST_U64
+	test_illegal(u64, 0x5a5b5c5d6a6b6c6d);
+#endif
+#undef test_illegal
+}
+
+static int usercopy_test_init(struct kunit *test)
+{
+	struct usercopy_test_priv *priv;
+	unsigned long user_addr;
+
+	priv = kunit_kzalloc(test, sizeof(*priv), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, priv);
+	test->priv = priv;
+	priv->size = PAGE_SIZE * 2;
+
+	priv->kmem = kunit_kmalloc(test, priv->size, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, priv->kmem);
+
+	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;
+
+	return 0;
+}
+
+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");