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fortify: Add KUnit test for FORTIFY_SOURCE internals

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Add lib/fortify_kunit.c KUnit test for checking the expected behavioral
characteristics of FORTIFY_SOURCE internals.

Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Tom Rix <trix@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: "Steven Rostedt (Google)" <rostedt@goodmis.org>
Cc: Yury Norov <yury.norov@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Sander Vanheule <sander@svanheule.net>
Cc: linux-hardening@vger.kernel.org
Cc: llvm@lists.linux.dev
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook 2022-09-02 13:02:26 -07:00
parent d07c0acb4f
commit 875bfd5276
4 changed files with 88 additions and 0 deletions
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1
MAINTAINERS
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@ -8002,6 +8002,7 @@ L: linux-hardening@vger.kernel.org
S: Supported
T: git git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/hardening
F: include/linux/fortify-string.h
F: lib/fortify_kunit.c
F: lib/test_fortify/*
F: scripts/test_fortify.sh
K: \b__NO_FORTIFY\b

9
lib/Kconfig.debug
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@ -2542,6 +2542,15 @@ config STACKINIT_KUNIT_TEST
CONFIG_GCC_PLUGIN_STRUCTLEAK, CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF,
or CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL.
config FORTIFY_KUNIT_TEST
tristate "Test fortified str*() and mem*() function internals at runtime" if !KUNIT_ALL_TESTS
depends on KUNIT && FORTIFY_SOURCE
default KUNIT_ALL_TESTS
help
Builds unit tests for checking internals of FORTIFY_SOURCE as used
by the str*() and mem*() family of functions. For testing runtime
traps of FORTIFY_SOURCE, see LKDTM's "FORTIFY_*" tests.
config TEST_UDELAY
tristate "udelay test driver"
help

1
lib/Makefile
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@ -381,6 +381,7 @@ obj-$(CONFIG_IS_SIGNED_TYPE_KUNIT_TEST) += is_signed_type_kunit.o
obj-$(CONFIG_OVERFLOW_KUNIT_TEST) += overflow_kunit.o
CFLAGS_stackinit_kunit.o += $(call cc-disable-warning, switch-unreachable)
obj-$(CONFIG_STACKINIT_KUNIT_TEST) += stackinit_kunit.o
obj-$(CONFIG_FORTIFY_KUNIT_TEST) += fortify_kunit.o
obj-$(CONFIG_GENERIC_LIB_DEVMEM_IS_ALLOWED) += devmem_is_allowed.o

77
lib/fortify_kunit.c Normal file
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@ -0,0 +1,77 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Runtime test cases for CONFIG_FORTIFY_SOURCE that aren't expected to
* Oops the kernel on success. (For those, see 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
#include <kunit/test.h>
#include <linux/string.h>
#include <linux/init.h>
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";
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(saved_command_line), 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);
}
static struct kunit_case fortify_test_cases[] = {
KUNIT_CASE(known_sizes_test),
KUNIT_CASE(control_flow_split_test),
{}
};
static struct kunit_suite fortify_test_suite = {
.name = "fortify",
.test_cases = fortify_test_cases,
};
kunit_test_suite(fortify_test_suite);
MODULE_LICENSE("GPL");