[PATCH 2/2] usercopy: Convert test_user_copy to KUnit test

Kees Cook
2024-05-19T19:12:57Z

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

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
Signed-off-by: Kees Cook <keescook@chromium.org>
---
MAINTAINERS | 1 +
lib/Kconfig.debug | 21 +-
lib/Makefile | 2 +-
lib/{test_user_copy.c => usercopy_kunit.c} | 252 ++++++++++-----------
4 files changed, 133 insertions(+), 143 deletions(-)
rename lib/{test_user_copy.c => usercopy_kunit.c} (52%)

diff --git a/MAINTAINERS b/MAINTAINERS
index 7c121493f43d..73995b807e5a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11761,6 +11761,7 @@ 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 c63a5fbf1f1c..fd974480aa45 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2460,18 +2460,6 @@ 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
@@ -2779,6 +2767,15 @@ 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 ffc6b2341b45..6287bd6be5d7 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
@@ -406,6 +405,7 @@ obj-$(CONFIG_FORTIFY_KUNIT_TEST) += fortify_kunit.o
obj-$(CONFIG_STRCAT_KUNIT_TEST) += strcat_kunit.o
obj-$(CONFIG_STRSCPY_KUNIT_TEST) += strscpy_kunit.o
obj-$(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/usercopy_kunit.c
similarity index 52%
rename from lib/test_user_copy.c
rename to lib/usercopy_kunit.c
index 5ff04d8fe971..515df08b3190 100644
--- a/lib/test_user_copy.c
+++ b/lib/usercopy_kunit.c
@@ -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.
@@ -31,11 +31,17 @@
# define TEST_U64
#endif

+struct usercopy_test_priv {
+ char *kmem;
+ char __user *umem;
+ size_t size;
+};
+
#define test(condition, msg, ...) \
({ \
int cond = (condition); \
if (cond) \
- pr_warn("[%d] " msg "\n", __LINE__, ##__VA_ARGS__); \
+ KUNIT_EXPECT_FALSE_MSG(test, cond, msg, ##__VA_ARGS__); \
cond; \
})

@@ -44,13 +50,16 @@ 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
@@ -84,8 +93,8 @@ 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),
- "legitimate copy_to_user failed");
+ 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++) {
@@ -93,35 +102,32 @@ 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,
- "check_nonzero_user(=%d) != memchr_inv(=%d) mismatch (start=%zu, end=%zu)",
- retval, expected, start, end);
+ KUNIT_EXPECT_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 +137,9 @@ 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_EQ_MSG(test, memcmp(kmem, expected, ksize), 0,
"copy_struct_from_user(usize == ksize) gives unexpected copy");

/* Old userspace case -- (usize < ksize). */
@@ -144,9 +150,9 @@ 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_EQ_MSG(test, memcmp(kmem, expected, ksize), 0,
"copy_struct_from_user(usize < ksize) gives unexpected copy");

/* New userspace (-E2BIG) case -- (usize > ksize). */
@@ -154,7 +160,7 @@ 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 +168,46 @@ 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_EQ_MSG(test, memcmp(kmem, expected, ksize), 0,
"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)
+/*
+ * Legitimate usage: none of these copies should fail.
+ */
+static void usercopy_test_valid(struct kunit *test)
{
- 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;
- }
+ struct usercopy_test_priv *priv = test->priv;
+ char __user *usermem = priv->umem;
+ char *kmem = priv->kmem;

- 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");
+ 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),
- "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); \
- } \
+ KUNIT_EXPECT_EQ_MSG(test, 0, copy_from_user(kmem, usermem, PAGE_SIZE),
+ "legitimate copy_from_user failed");
+ KUNIT_EXPECT_EQ_MSG(test, 0, memcmp(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);
@@ -243,27 +217,29 @@ 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.
- */
+/*
+ * 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;

/* 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_EQ_MSG(test, memcmp(kmem + PAGE_SIZE, kmem, PAGE_SIZE), 0,
"zeroing failure for illegal all-kernel copy_from_user");

#if 0
@@ -273,29 +249,25 @@ 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); \
+ 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), \
+ KUNIT_EXPECT_NE_MSG(test, put_user(val_##size, (size __user *)kmem), 0, \
"illegal put_user (" #size ") passed"); \
} while (0)

@@ -306,26 +278,46 @@ 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);
+ if (!priv)
+ return -ENOMEM;
+ 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_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);
-
+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 <keescook@chromium.org>");
MODULE_LICENSE("GPL");
--
2.34.1