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

David Gow
2024-06-08T08:44:25Z

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On Mon, 20 May 2024 at 03:12, Kees Cook <keescook@chromium.org> wrote:
>
> 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>
> ---

This fails here on i386:
> # usercopy_test_invalid: EXPECTATION FAILED at lib/usercopy_kunit.c:278
> Expected val_u64 == 0, but
> val_u64 == -60129542144 (0xfffffff200000000)

It also seems to be hanging somewhere in usercopy_test_invalid on my
m68k/qemu setup:
./tools/testing/kunit/kunit.py run --build_dir=.kunit-m68k --arch m68k usercopy

Otherwise, it looks fine. Maybe it'd make sense to split some of the
tests up a bit more, but it's a matter of taste (and only really an
advantage for debugging hangs where more detailed progress is nice).

With those architecture-specific hangs either fixed, or documented (if
they're actual problems, not issues with the test), this is:

Reviewed-by: David Gow <davidgow@google.com>

Cheers,
-- David

> 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.
> +

FYI: Checkpatch is whinging that this help text isn't detailed enough.
(I'm not sure what else you could add, though...)

> 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
>

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