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linux/lib/fortify_kunit.c
Kees Cook 3d965b33e4 fortify: Improve buffer overflow reporting 
Improve the reporting of buffer overflows under CONFIG_FORTIFY_SOURCE to
help accelerate debugging efforts. The calculations are all just sitting
in registers anyway, so pass them along to the function to be reported.

For example, before:

  detected buffer overflow in memcpy

and after:

  memcpy: detected buffer overflow: 4096 byte read of buffer size 1

Link: https://lore.kernel.org/r/20230407192717.636137-10-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
2024-02-29 13:38:02 -08:00

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// SPDX-License-Identifier: GPL-2.0
/*
* Runtime test cases for CONFIG_FORTIFY_SOURCE. For testing memcpy(),
* see FORTIFY_MEM_* tests in LKDTM (drivers/misc/lkdtm/fortify.c).
*
* For corner cases with UBSAN, try testing with:
*
* ./tools/testing/kunit/kunit.py run --arch=x86_64 \
* --kconfig_add CONFIG_FORTIFY_SOURCE=y \
* --kconfig_add CONFIG_UBSAN=y \
* --kconfig_add CONFIG_UBSAN_TRAP=y \
* --kconfig_add CONFIG_UBSAN_BOUNDS=y \
* --kconfig_add CONFIG_UBSAN_LOCAL_BOUNDS=y \
* --make_options LLVM=1 fortify
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
/* Redefine fortify_panic() to track failures. */
void fortify_add_kunit_error(int write);
#define fortify_panic(func, write, avail, size, retfail) do { \
__fortify_report(FORTIFY_REASON(func, write), avail, size); \
fortify_add_kunit_error(write); \
return (retfail); \
} while (0)
#include <kunit/device.h>
#include <kunit/test.h>
#include <kunit/test-bug.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/vmalloc.h>
/* Handle being built without CONFIG_FORTIFY_SOURCE */
#ifndef __compiletime_strlen
# define __compiletime_strlen __builtin_strlen
#endif
static struct kunit_resource read_resource;
static struct kunit_resource write_resource;
static int fortify_read_overflows;
static int fortify_write_overflows;
static const char array_of_10[] = "this is 10";
static const char *ptr_of_11 = "this is 11!";
static char array_unknown[] = "compiler thinks I might change";
void fortify_add_kunit_error(int write)
{
struct kunit_resource *resource;
struct kunit *current_test;
current_test = kunit_get_current_test();
if (!current_test)
return;
resource = kunit_find_named_resource(current_test,
write ? "fortify_write_overflows"
: "fortify_read_overflows");
if (!resource)
return;
(*(int *)resource->data)++;
kunit_put_resource(resource);
}
static void known_sizes_test(struct kunit *test)
{
KUNIT_EXPECT_EQ(test, __compiletime_strlen("88888888"), 8);
KUNIT_EXPECT_EQ(test, __compiletime_strlen(array_of_10), 10);
KUNIT_EXPECT_EQ(test, __compiletime_strlen(ptr_of_11), 11);
KUNIT_EXPECT_EQ(test, __compiletime_strlen(array_unknown), SIZE_MAX);
/* Externally defined and dynamically sized string pointer: */
KUNIT_EXPECT_EQ(test, __compiletime_strlen(test->name), SIZE_MAX);
}
/* This is volatile so the optimizer can't perform DCE below. */
static volatile int pick;
/* Not inline to keep optimizer from figuring out which string we want. */
static noinline size_t want_minus_one(int pick)
{
const char *str;
switch (pick) {
case 1:
str = "4444";
break;
case 2:
str = "333";
break;
default:
str = "1";
break;
}
return __compiletime_strlen(str);
}
static void control_flow_split_test(struct kunit *test)
{
KUNIT_EXPECT_EQ(test, want_minus_one(pick), SIZE_MAX);
}
#define KUNIT_EXPECT_BOS(test, p, expected, name) \
KUNIT_EXPECT_EQ_MSG(test, __builtin_object_size(p, 1), \
expected, \
"__alloc_size() not working with __bos on " name "\n")
#if !__has_builtin(__builtin_dynamic_object_size)
#define KUNIT_EXPECT_BDOS(test, p, expected, name) \
/* Silence "unused variable 'expected'" warning. */ \
KUNIT_EXPECT_EQ(test, expected, expected)
#else
#define KUNIT_EXPECT_BDOS(test, p, expected, name) \
KUNIT_EXPECT_EQ_MSG(test, __builtin_dynamic_object_size(p, 1), \
expected, \
"__alloc_size() not working with __bdos on " name "\n")
#endif
/* If the execpted size is a constant value, __bos can see it. */
#define check_const(_expected, alloc, free) do { \
size_t expected = (_expected); \
void *p = alloc; \
KUNIT_EXPECT_TRUE_MSG(test, p != NULL, #alloc " failed?!\n"); \
KUNIT_EXPECT_BOS(test, p, expected, #alloc); \
KUNIT_EXPECT_BDOS(test, p, expected, #alloc); \
free; \
} while (0)
/* If the execpted size is NOT a constant value, __bos CANNOT see it. */
#define check_dynamic(_expected, alloc, free) do { \
size_t expected = (_expected); \
void *p = alloc; \
KUNIT_EXPECT_TRUE_MSG(test, p != NULL, #alloc " failed?!\n"); \
KUNIT_EXPECT_BOS(test, p, SIZE_MAX, #alloc); \
KUNIT_EXPECT_BDOS(test, p, expected, #alloc); \
free; \
} while (0)
/* Assortment of constant-value kinda-edge cases. */
#define CONST_TEST_BODY(TEST_alloc) do { \
/* Special-case vmalloc()-family to skip 0-sized allocs. */ \
if (strcmp(#TEST_alloc, "TEST_vmalloc") != 0) \
TEST_alloc(check_const, 0, 0); \
TEST_alloc(check_const, 1, 1); \
TEST_alloc(check_const, 128, 128); \
TEST_alloc(check_const, 1023, 1023); \
TEST_alloc(check_const, 1025, 1025); \
TEST_alloc(check_const, 4096, 4096); \
TEST_alloc(check_const, 4097, 4097); \
} while (0)
static volatile size_t zero_size;
static volatile size_t unknown_size = 50;
#if !__has_builtin(__builtin_dynamic_object_size)
#define DYNAMIC_TEST_BODY(TEST_alloc) \
kunit_skip(test, "Compiler is missing __builtin_dynamic_object_size() support\n")
#else
#define DYNAMIC_TEST_BODY(TEST_alloc) do { \
size_t size = unknown_size; \
\
/* \
* Expected size is "size" in each test, before it is then \
* internally incremented in each test. Requires we disable \
* -Wunsequenced. \
*/ \
TEST_alloc(check_dynamic, size, size++); \
/* Make sure incrementing actually happened. */ \
KUNIT_EXPECT_NE(test, size, unknown_size); \
} while (0)
#endif
#define DEFINE_ALLOC_SIZE_TEST_PAIR(allocator) \
static void alloc_size_##allocator##_const_test(struct kunit *test) \
{ \
CONST_TEST_BODY(TEST_##allocator); \
} \
static void alloc_size_##allocator##_dynamic_test(struct kunit *test) \
{ \
DYNAMIC_TEST_BODY(TEST_##allocator); \
}
#define TEST_kmalloc(checker, expected_size, alloc_size) do { \
gfp_t gfp = GFP_KERNEL | __GFP_NOWARN; \
void *orig; \
size_t len; \
\
checker(expected_size, kmalloc(alloc_size, gfp), \
kfree(p)); \
checker(expected_size, \
kmalloc_node(alloc_size, gfp, NUMA_NO_NODE), \
kfree(p)); \
checker(expected_size, kzalloc(alloc_size, gfp), \
kfree(p)); \
checker(expected_size, \
kzalloc_node(alloc_size, gfp, NUMA_NO_NODE), \
kfree(p)); \
checker(expected_size, kcalloc(1, alloc_size, gfp), \
kfree(p)); \
checker(expected_size, kcalloc(alloc_size, 1, gfp), \
kfree(p)); \
checker(expected_size, \
kcalloc_node(1, alloc_size, gfp, NUMA_NO_NODE), \
kfree(p)); \
checker(expected_size, \
kcalloc_node(alloc_size, 1, gfp, NUMA_NO_NODE), \
kfree(p)); \
checker(expected_size, kmalloc_array(1, alloc_size, gfp), \
kfree(p)); \
checker(expected_size, kmalloc_array(alloc_size, 1, gfp), \
kfree(p)); \
checker(expected_size, \
kmalloc_array_node(1, alloc_size, gfp, NUMA_NO_NODE), \
kfree(p)); \
checker(expected_size, \
kmalloc_array_node(alloc_size, 1, gfp, NUMA_NO_NODE), \
kfree(p)); \
checker(expected_size, __kmalloc(alloc_size, gfp), \
kfree(p)); \
checker(expected_size, \
__kmalloc_node(alloc_size, gfp, NUMA_NO_NODE), \
kfree(p)); \
\
orig = kmalloc(alloc_size, gfp); \
KUNIT_EXPECT_TRUE(test, orig != NULL); \
checker((expected_size) * 2, \
krealloc(orig, (alloc_size) * 2, gfp), \
kfree(p)); \
orig = kmalloc(alloc_size, gfp); \
KUNIT_EXPECT_TRUE(test, orig != NULL); \
checker((expected_size) * 2, \
krealloc_array(orig, 1, (alloc_size) * 2, gfp), \
kfree(p)); \
orig = kmalloc(alloc_size, gfp); \
KUNIT_EXPECT_TRUE(test, orig != NULL); \
checker((expected_size) * 2, \
krealloc_array(orig, (alloc_size) * 2, 1, gfp), \
kfree(p)); \
\
len = 11; \
/* Using memdup() with fixed size, so force unknown length. */ \
if (!__builtin_constant_p(expected_size)) \
len += zero_size; \
checker(len, kmemdup("hello there", len, gfp), kfree(p)); \
} while (0)
DEFINE_ALLOC_SIZE_TEST_PAIR(kmalloc)
/* Sizes are in pages, not bytes. */
#define TEST_vmalloc(checker, expected_pages, alloc_pages) do { \
gfp_t gfp = GFP_KERNEL | __GFP_NOWARN; \
checker((expected_pages) * PAGE_SIZE, \
vmalloc((alloc_pages) * PAGE_SIZE), vfree(p)); \
checker((expected_pages) * PAGE_SIZE, \
vzalloc((alloc_pages) * PAGE_SIZE), vfree(p)); \
checker((expected_pages) * PAGE_SIZE, \
__vmalloc((alloc_pages) * PAGE_SIZE, gfp), vfree(p)); \
} while (0)
DEFINE_ALLOC_SIZE_TEST_PAIR(vmalloc)
/* Sizes are in pages (and open-coded for side-effects), not bytes. */
#define TEST_kvmalloc(checker, expected_pages, alloc_pages) do { \
gfp_t gfp = GFP_KERNEL | __GFP_NOWARN; \
size_t prev_size; \
void *orig; \
\
checker((expected_pages) * PAGE_SIZE, \
kvmalloc((alloc_pages) * PAGE_SIZE, gfp), \
vfree(p)); \
checker((expected_pages) * PAGE_SIZE, \
kvmalloc_node((alloc_pages) * PAGE_SIZE, gfp, NUMA_NO_NODE), \
vfree(p)); \
checker((expected_pages) * PAGE_SIZE, \
kvzalloc((alloc_pages) * PAGE_SIZE, gfp), \
vfree(p)); \
checker((expected_pages) * PAGE_SIZE, \
kvzalloc_node((alloc_pages) * PAGE_SIZE, gfp, NUMA_NO_NODE), \
vfree(p)); \
checker((expected_pages) * PAGE_SIZE, \
kvcalloc(1, (alloc_pages) * PAGE_SIZE, gfp), \
vfree(p)); \
checker((expected_pages) * PAGE_SIZE, \
kvcalloc((alloc_pages) * PAGE_SIZE, 1, gfp), \
vfree(p)); \
checker((expected_pages) * PAGE_SIZE, \
kvmalloc_array(1, (alloc_pages) * PAGE_SIZE, gfp), \
vfree(p)); \
checker((expected_pages) * PAGE_SIZE, \
kvmalloc_array((alloc_pages) * PAGE_SIZE, 1, gfp), \
vfree(p)); \
\
prev_size = (expected_pages) * PAGE_SIZE; \
orig = kvmalloc(prev_size, gfp); \
KUNIT_EXPECT_TRUE(test, orig != NULL); \
checker(((expected_pages) * PAGE_SIZE) * 2, \
kvrealloc(orig, prev_size, \
((alloc_pages) * PAGE_SIZE) * 2, gfp), \
kvfree(p)); \
} while (0)
DEFINE_ALLOC_SIZE_TEST_PAIR(kvmalloc)
#define TEST_devm_kmalloc(checker, expected_size, alloc_size) do { \
gfp_t gfp = GFP_KERNEL | __GFP_NOWARN; \
const char dev_name[] = "fortify-test"; \
struct device *dev; \
void *orig; \
size_t len; \
\
/* Create dummy device for devm_kmalloc()-family tests. */ \
dev = kunit_device_register(test, dev_name); \
KUNIT_ASSERT_FALSE_MSG(test, IS_ERR(dev), \
"Cannot register test device\n"); \
\
checker(expected_size, devm_kmalloc(dev, alloc_size, gfp), \
devm_kfree(dev, p)); \
checker(expected_size, devm_kzalloc(dev, alloc_size, gfp), \
devm_kfree(dev, p)); \
checker(expected_size, \
devm_kmalloc_array(dev, 1, alloc_size, gfp), \
devm_kfree(dev, p)); \
checker(expected_size, \
devm_kmalloc_array(dev, alloc_size, 1, gfp), \
devm_kfree(dev, p)); \
checker(expected_size, \
devm_kcalloc(dev, 1, alloc_size, gfp), \
devm_kfree(dev, p)); \
checker(expected_size, \
devm_kcalloc(dev, alloc_size, 1, gfp), \
devm_kfree(dev, p)); \
\
orig = devm_kmalloc(dev, alloc_size, gfp); \
KUNIT_EXPECT_TRUE(test, orig != NULL); \
checker((expected_size) * 2, \
devm_krealloc(dev, orig, (alloc_size) * 2, gfp), \
devm_kfree(dev, p)); \
\
len = 4; \
/* Using memdup() with fixed size, so force unknown length. */ \
if (!__builtin_constant_p(expected_size)) \
len += zero_size; \
checker(len, devm_kmemdup(dev, "Ohai", len, gfp), \
devm_kfree(dev, p)); \
\
kunit_device_unregister(test, dev); \
} while (0)
DEFINE_ALLOC_SIZE_TEST_PAIR(devm_kmalloc)
/*
* We can't have an array at the end of a structure or else
* builds without -fstrict-flex-arrays=3 will report them as
* being an unknown length. Additionally, add bytes before
* and after the string to catch over/underflows if tests
* fail.
*/
struct fortify_padding {
unsigned long bytes_before;
char buf[32];
unsigned long bytes_after;
};
/* Force compiler into not being able to resolve size at compile-time. */
static volatile int unconst;
static void strlen_test(struct kunit *test)
{
struct fortify_padding pad = { };
int i, end = sizeof(pad.buf) - 1;
/* Fill 31 bytes with valid characters. */
for (i = 0; i < sizeof(pad.buf) - 1; i++)
pad.buf[i] = i + '0';
/* Trailing bytes are still %NUL. */
KUNIT_EXPECT_EQ(test, pad.buf[end], '\0');
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
/* String is terminated, so strlen() is valid. */
KUNIT_EXPECT_EQ(test, strlen(pad.buf), end);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
/* Make string unterminated, and recount. */
pad.buf[end] = 'A';
end = sizeof(pad.buf);
KUNIT_EXPECT_EQ(test, strlen(pad.buf), end);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 1);
}
static void strnlen_test(struct kunit *test)
{
struct fortify_padding pad = { };
int i, end = sizeof(pad.buf) - 1;
/* Fill 31 bytes with valid characters. */
for (i = 0; i < sizeof(pad.buf) - 1; i++)
pad.buf[i] = i + '0';
/* Trailing bytes are still %NUL. */
KUNIT_EXPECT_EQ(test, pad.buf[end], '\0');
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
/* String is terminated, so strnlen() is valid. */
KUNIT_EXPECT_EQ(test, strnlen(pad.buf, sizeof(pad.buf)), end);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
/* A truncated strnlen() will be safe, too. */
KUNIT_EXPECT_EQ(test, strnlen(pad.buf, sizeof(pad.buf) / 2),
sizeof(pad.buf) / 2);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
/* Make string unterminated, and recount. */
pad.buf[end] = 'A';
end = sizeof(pad.buf);
/* Reading beyond with strncpy() will fail. */
KUNIT_EXPECT_EQ(test, strnlen(pad.buf, end + 1), end);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 1);
KUNIT_EXPECT_EQ(test, strnlen(pad.buf, end + 2), end);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 2);
/* Early-truncated is safe still, though. */
KUNIT_EXPECT_EQ(test, strnlen(pad.buf, end), end);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 2);
end = sizeof(pad.buf) / 2;
KUNIT_EXPECT_EQ(test, strnlen(pad.buf, end), end);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 2);
}
static void strcpy_test(struct kunit *test)
{
struct fortify_padding pad = { };
char src[sizeof(pad.buf) + 1] = { };
int i;
/* Fill 31 bytes with valid characters. */
for (i = 0; i < sizeof(src) - 2; i++)
src[i] = i + '0';
/* Destination is %NUL-filled to start with. */
KUNIT_EXPECT_EQ(test, pad.bytes_before, 0);
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 3], '\0');
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
/* Legitimate strcpy() 1 less than of max size. */
KUNIT_ASSERT_TRUE(test, strcpy(pad.buf, src)
== pad.buf);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
/* Only last byte should be %NUL */
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
src[sizeof(src) - 2] = 'A';
/* But now we trip the overflow checking. */
KUNIT_ASSERT_TRUE(test, strcpy(pad.buf, src)
== pad.buf);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 1);
/* Trailing %NUL -- thanks to FORTIFY. */
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
/* And we will not have gone beyond. */
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
src[sizeof(src) - 1] = 'A';
/* And for sure now, two bytes past. */
KUNIT_ASSERT_TRUE(test, strcpy(pad.buf, src)
== pad.buf);
/*
* Which trips both the strlen() on the unterminated src,
* and the resulting copy attempt.
*/
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 1);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 2);
/* Trailing %NUL -- thanks to FORTIFY. */
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
/* And we will not have gone beyond. */
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
}
static void strncpy_test(struct kunit *test)
{
struct fortify_padding pad = { };
char src[] = "Copy me fully into a small buffer and I will overflow!";
/* Destination is %NUL-filled to start with. */
KUNIT_EXPECT_EQ(test, pad.bytes_before, 0);
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 3], '\0');
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
/* Legitimate strncpy() 1 less than of max size. */
KUNIT_ASSERT_TRUE(test, strncpy(pad.buf, src,
sizeof(pad.buf) + unconst - 1)
== pad.buf);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
/* Only last byte should be %NUL */
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
/* Legitimate (though unterminated) max-size strncpy. */
KUNIT_ASSERT_TRUE(test, strncpy(pad.buf, src,
sizeof(pad.buf) + unconst)
== pad.buf);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
/* No trailing %NUL -- thanks strncpy API. */
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
/* But we will not have gone beyond. */
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
/* Now verify that FORTIFY is working... */
KUNIT_ASSERT_TRUE(test, strncpy(pad.buf, src,
sizeof(pad.buf) + unconst + 1)
== pad.buf);
/* Should catch the overflow. */
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 1);
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
/* And we will not have gone beyond. */
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
/* And further... */
KUNIT_ASSERT_TRUE(test, strncpy(pad.buf, src,
sizeof(pad.buf) + unconst + 2)
== pad.buf);
/* Should catch the overflow. */
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 2);
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
/* And we will not have gone beyond. */
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
}
static void strscpy_test(struct kunit *test)
{
struct fortify_padding pad = { };
char src[] = "Copy me fully into a small buffer and I will overflow!";
/* Destination is %NUL-filled to start with. */
KUNIT_EXPECT_EQ(test, pad.bytes_before, 0);
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 3], '\0');
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
/* Legitimate strscpy() 1 less than of max size. */
KUNIT_ASSERT_EQ(test, strscpy(pad.buf, src,
sizeof(pad.buf) + unconst - 1),
-E2BIG);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
/* Keeping space for %NUL, last two bytes should be %NUL */
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
/* Legitimate max-size strscpy. */
KUNIT_ASSERT_EQ(test, strscpy(pad.buf, src,
sizeof(pad.buf) + unconst),
-E2BIG);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
/* A trailing %NUL will exist. */
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
/* Now verify that FORTIFY is working... */
KUNIT_ASSERT_EQ(test, strscpy(pad.buf, src,
sizeof(pad.buf) + unconst + 1),
-E2BIG);
/* Should catch the overflow. */
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 1);
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
/* And we will not have gone beyond. */
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
/* And much further... */
KUNIT_ASSERT_EQ(test, strscpy(pad.buf, src,
sizeof(src) * 2 + unconst),
-E2BIG);
/* Should catch the overflow. */
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 2);
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
/* And we will not have gone beyond. */
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
}
static void strcat_test(struct kunit *test)
{
struct fortify_padding pad = { };
char src[sizeof(pad.buf) / 2] = { };
char one[] = "A";
char two[] = "BC";
int i;
/* Fill 15 bytes with valid characters. */
for (i = 0; i < sizeof(src) - 1; i++)
src[i] = i + 'A';
/* Destination is %NUL-filled to start with. */
KUNIT_EXPECT_EQ(test, pad.bytes_before, 0);
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 3], '\0');
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
/* Legitimate strcat() using less than half max size. */
KUNIT_ASSERT_TRUE(test, strcat(pad.buf, src) == pad.buf);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
/* Legitimate strcat() now 2 bytes shy of end. */
KUNIT_ASSERT_TRUE(test, strcat(pad.buf, src) == pad.buf);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
/* Last two bytes should be %NUL */
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
/* Add one more character to the end. */
KUNIT_ASSERT_TRUE(test, strcat(pad.buf, one) == pad.buf);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
/* Last byte should be %NUL */
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
/* And this one char will overflow. */
KUNIT_ASSERT_TRUE(test, strcat(pad.buf, one) == pad.buf);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 1);
/* Last byte should be %NUL thanks to FORTIFY. */
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
/* And adding two will overflow more. */
KUNIT_ASSERT_TRUE(test, strcat(pad.buf, two) == pad.buf);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 2);
/* Last byte should be %NUL thanks to FORTIFY. */
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
}
static void strncat_test(struct kunit *test)
{
struct fortify_padding pad = { };
char src[sizeof(pad.buf)] = { };
int i, partial;
/* Fill 31 bytes with valid characters. */
partial = sizeof(src) / 2 - 1;
for (i = 0; i < partial; i++)
src[i] = i + 'A';
/* Destination is %NUL-filled to start with. */
KUNIT_EXPECT_EQ(test, pad.bytes_before, 0);
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 3], '\0');
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
/* Legitimate strncat() using less than half max size. */
KUNIT_ASSERT_TRUE(test, strncat(pad.buf, src, partial) == pad.buf);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
/* Legitimate strncat() now 2 bytes shy of end. */
KUNIT_ASSERT_TRUE(test, strncat(pad.buf, src, partial) == pad.buf);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
/* Last two bytes should be %NUL */
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
/* Add one more character to the end. */
KUNIT_ASSERT_TRUE(test, strncat(pad.buf, src, 1) == pad.buf);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
/* Last byte should be %NUL */
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
/* And this one char will overflow. */
KUNIT_ASSERT_TRUE(test, strncat(pad.buf, src, 1) == pad.buf);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 1);
/* Last byte should be %NUL thanks to FORTIFY. */
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
/* And adding two will overflow more. */
KUNIT_ASSERT_TRUE(test, strncat(pad.buf, src, 2) == pad.buf);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 2);
/* Last byte should be %NUL thanks to FORTIFY. */
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
/* Force an unterminated destination, and overflow. */
pad.buf[sizeof(pad.buf) - 1] = 'A';
KUNIT_ASSERT_TRUE(test, strncat(pad.buf, src, 1) == pad.buf);
/* This will have tripped both strlen() and strcat(). */
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 1);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 3);
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
/* But we should not go beyond the end. */
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
}
static void strlcat_test(struct kunit *test)
{
struct fortify_padding pad = { };
char src[sizeof(pad.buf)] = { };
int i, partial;
int len = sizeof(pad.buf) + unconst;
/* Fill 15 bytes with valid characters. */
partial = sizeof(src) / 2 - 1;
for (i = 0; i < partial; i++)
src[i] = i + 'A';
/* Destination is %NUL-filled to start with. */
KUNIT_EXPECT_EQ(test, pad.bytes_before, 0);
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 3], '\0');
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
/* Legitimate strlcat() using less than half max size. */
KUNIT_ASSERT_EQ(test, strlcat(pad.buf, src, len), partial);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
/* Legitimate strlcat() now 2 bytes shy of end. */
KUNIT_ASSERT_EQ(test, strlcat(pad.buf, src, len), partial * 2);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
/* Last two bytes should be %NUL */
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
/* Add one more character to the end. */
KUNIT_ASSERT_EQ(test, strlcat(pad.buf, "Q", len), partial * 2 + 1);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 0);
/* Last byte should be %NUL */
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
/* And this one char will overflow. */
KUNIT_ASSERT_EQ(test, strlcat(pad.buf, "V", len * 2), len);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 1);
/* Last byte should be %NUL thanks to FORTIFY. */
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
/* And adding two will overflow more. */
KUNIT_ASSERT_EQ(test, strlcat(pad.buf, "QQ", len * 2), len + 1);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 2);
/* Last byte should be %NUL thanks to FORTIFY. */
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
/* Force an unterminated destination, and overflow. */
pad.buf[sizeof(pad.buf) - 1] = 'A';
KUNIT_ASSERT_EQ(test, strlcat(pad.buf, "TT", len * 2), len + 2);
/* This will have tripped both strlen() and strlcat(). */
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 2);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 2);
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 1], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 2], '\0');
KUNIT_EXPECT_NE(test, pad.buf[sizeof(pad.buf) - 3], '\0');
/* But we should not go beyond the end. */
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
/* Force an unterminated source, and overflow. */
memset(src, 'B', sizeof(src));
pad.buf[sizeof(pad.buf) - 1] = '\0';
KUNIT_ASSERT_EQ(test, strlcat(pad.buf, src, len * 3), len - 1 + sizeof(src));
/* This will have tripped both strlen() and strlcat(). */
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 3);
KUNIT_EXPECT_EQ(test, fortify_write_overflows, 3);
KUNIT_EXPECT_EQ(test, pad.buf[sizeof(pad.buf) - 1], '\0');
/* But we should not go beyond the end. */
KUNIT_EXPECT_EQ(test, pad.bytes_after, 0);
}
static void memscan_test(struct kunit *test)
{
char haystack[] = "Where oh where is my memory range?";
char *mem = haystack + strlen("Where oh where is ");
char needle = 'm';
size_t len = sizeof(haystack) + unconst;
KUNIT_ASSERT_PTR_EQ(test, memscan(haystack, needle, len),
mem);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
/* Catch too-large range. */
KUNIT_ASSERT_PTR_EQ(test, memscan(haystack, needle, len + 1),
NULL);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 1);
KUNIT_ASSERT_PTR_EQ(test, memscan(haystack, needle, len * 2),
NULL);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 2);
}
static void memchr_test(struct kunit *test)
{
char haystack[] = "Where oh where is my memory range?";
char *mem = haystack + strlen("Where oh where is ");
char needle = 'm';
size_t len = sizeof(haystack) + unconst;
KUNIT_ASSERT_PTR_EQ(test, memchr(haystack, needle, len),
mem);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
/* Catch too-large range. */
KUNIT_ASSERT_PTR_EQ(test, memchr(haystack, needle, len + 1),
NULL);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 1);
KUNIT_ASSERT_PTR_EQ(test, memchr(haystack, needle, len * 2),
NULL);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 2);
}
static void memchr_inv_test(struct kunit *test)
{
char haystack[] = "Where oh where is my memory range?";
char *mem = haystack + 1;
char needle = 'W';
size_t len = sizeof(haystack) + unconst;
/* Normal search is okay. */
KUNIT_ASSERT_PTR_EQ(test, memchr_inv(haystack, needle, len),
mem);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
/* Catch too-large range. */
KUNIT_ASSERT_PTR_EQ(test, memchr_inv(haystack, needle, len + 1),
NULL);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 1);
KUNIT_ASSERT_PTR_EQ(test, memchr_inv(haystack, needle, len * 2),
NULL);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 2);
}
static void memcmp_test(struct kunit *test)
{
char one[] = "My mind is going ...";
char two[] = "My mind is going ... I can feel it.";
size_t one_len = sizeof(one) + unconst - 1;
size_t two_len = sizeof(two) + unconst - 1;
/* We match the first string (ignoring the %NUL). */
KUNIT_ASSERT_EQ(test, memcmp(one, two, one_len), 0);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
/* Still in bounds, but no longer matching. */
KUNIT_ASSERT_EQ(test, memcmp(one, two, one_len + 1), -32);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
/* Catch too-large ranges. */
KUNIT_ASSERT_EQ(test, memcmp(one, two, one_len + 2), INT_MIN);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 1);
KUNIT_ASSERT_EQ(test, memcmp(two, one, two_len + 2), INT_MIN);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 2);
}
static void kmemdup_test(struct kunit *test)
{
char src[] = "I got Doom running on it!";
char *copy;
size_t len = sizeof(src) + unconst;
/* Copy is within bounds. */
copy = kmemdup(src, len, GFP_KERNEL);
KUNIT_EXPECT_NOT_NULL(test, copy);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
kfree(copy);
/* Without %NUL. */
copy = kmemdup(src, len - 1, GFP_KERNEL);
KUNIT_EXPECT_NOT_NULL(test, copy);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
kfree(copy);
/* Tiny bounds. */
copy = kmemdup(src, 1, GFP_KERNEL);
KUNIT_EXPECT_NOT_NULL(test, copy);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
kfree(copy);
/* Out of bounds by 1 byte. */
copy = kmemdup(src, len + 1, GFP_KERNEL);
KUNIT_EXPECT_NULL(test, copy);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 1);
kfree(copy);
/* Way out of bounds. */
copy = kmemdup(src, len * 2, GFP_KERNEL);
KUNIT_EXPECT_NULL(test, copy);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 2);
kfree(copy);
/* Starting offset causing out of bounds. */
copy = kmemdup(src + 1, len, GFP_KERNEL);
KUNIT_EXPECT_NULL(test, copy);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 3);
kfree(copy);
}
static int fortify_test_init(struct kunit *test)
{
if (!IS_ENABLED(CONFIG_FORTIFY_SOURCE))
kunit_skip(test, "Not built with CONFIG_FORTIFY_SOURCE=y");
fortify_read_overflows = 0;
kunit_add_named_resource(test, NULL, NULL, &read_resource,
"fortify_read_overflows",
&fortify_read_overflows);
fortify_write_overflows = 0;
kunit_add_named_resource(test, NULL, NULL, &write_resource,
"fortify_write_overflows",
&fortify_write_overflows);
return 0;
}
static struct kunit_case fortify_test_cases[] = {
KUNIT_CASE(known_sizes_test),
KUNIT_CASE(control_flow_split_test),
KUNIT_CASE(alloc_size_kmalloc_const_test),
KUNIT_CASE(alloc_size_kmalloc_dynamic_test),
KUNIT_CASE(alloc_size_vmalloc_const_test),
KUNIT_CASE(alloc_size_vmalloc_dynamic_test),
KUNIT_CASE(alloc_size_kvmalloc_const_test),
KUNIT_CASE(alloc_size_kvmalloc_dynamic_test),
KUNIT_CASE(alloc_size_devm_kmalloc_const_test),
KUNIT_CASE(alloc_size_devm_kmalloc_dynamic_test),
KUNIT_CASE(strlen_test),
KUNIT_CASE(strnlen_test),
KUNIT_CASE(strcpy_test),
KUNIT_CASE(strncpy_test),
KUNIT_CASE(strscpy_test),
KUNIT_CASE(strcat_test),
KUNIT_CASE(strncat_test),
KUNIT_CASE(strlcat_test),
/* skip memset: performs bounds checking on whole structs */
/* skip memcpy: still using warn-and-overwrite instead of hard-fail */
KUNIT_CASE(memscan_test),
KUNIT_CASE(memchr_test),
KUNIT_CASE(memchr_inv_test),
KUNIT_CASE(memcmp_test),
KUNIT_CASE(kmemdup_test),
{}
};
static struct kunit_suite fortify_test_suite = {
.name = "fortify",
.init = fortify_test_init,
.test_cases = fortify_test_cases,
};
kunit_test_suite(fortify_test_suite);
MODULE_LICENSE("GPL");
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