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Message-ID: <CABVgOS=Ru4Eu03T71svLA=j9jizGro44n3h59pQYw33QYPfLaQ@mail.gmail.com> Date: Sat, 3 Sep 2022 10:59:24 +0800 From: David Gow <davidgow@...gle.com> To: Kees Cook <keescook@...omium.org> Cc: Nick Desaulniers <ndesaulniers@...gle.com>, Nathan Chancellor <nathan@...nel.org>, Tom Rix <trix@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>, Vlastimil Babka <vbabka@...e.cz>, "Steven Rostedt (Google)" <rostedt@...dmis.org>, Yury Norov <yury.norov@...il.com>, Masami Hiramatsu <mhiramat@...nel.org>, Sander Vanheule <sander@...nheule.net>, linux-hardening@...r.kernel.org, llvm@...ts.linux.dev, Peter Zijlstra <peterz@...radead.org>, Josh Poimboeuf <jpoimboe@...nel.org>, Dan Williams <dan.j.williams@...el.com>, Isabella Basso <isabbasso@...eup.net>, Eric Dumazet <edumazet@...gle.com>, Rasmus Villemoes <linux@...musvillemoes.dk>, Eric Biggers <ebiggers@...gle.com>, Hannes Reinecke <hare@...e.de>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v2 2/3] fortify: Add KUnit test for FORTIFY_SOURCE internals On Sat, Sep 3, 2022 at 4:43 AM Kees Cook <keescook@...omium.org> wrote: > > Add lib/fortify_kunit.c KUnit test for checking the expected behavioral > characteristics of FORTIFY_SOURCE internals. > > Cc: Nick Desaulniers <ndesaulniers@...gle.com> > Cc: Nathan Chancellor <nathan@...nel.org> > Cc: Tom Rix <trix@...hat.com> > Cc: Andrew Morton <akpm@...ux-foundation.org> > Cc: Vlastimil Babka <vbabka@...e.cz> > Cc: "Steven Rostedt (Google)" <rostedt@...dmis.org> > Cc: David Gow <davidgow@...gle.com> > Cc: Yury Norov <yury.norov@...il.com> > Cc: Masami Hiramatsu <mhiramat@...nel.org> > Cc: Sander Vanheule <sander@...nheule.net> > Cc: linux-hardening@...r.kernel.org > Cc: llvm@...ts.linux.dev > Signed-off-by: Kees Cook <keescook@...omium.org> > --- Overall, this looks good. It's a bit of a shame FORTIFY_SOURCE doesn't work under UML, but I tested it on everything else I had to hand and it looked good. One tiny typo in a comment below, but otherwise this is: Reviewed-by: David Gow <davidgow@...gle.com> Cheers, -- David > MAINTAINERS | 1 + > lib/Kconfig.debug | 9 ++++++ > lib/Makefile | 1 + > lib/fortify_kunit.c | 77 +++++++++++++++++++++++++++++++++++++++++++++ > 4 files changed, 88 insertions(+) > create mode 100644 lib/fortify_kunit.c > > diff --git a/MAINTAINERS b/MAINTAINERS > index 9d7f64dc0efe..640115472199 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -8002,6 +8002,7 @@ L: linux-hardening@...r.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 > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index 36455953d306..1f267c0ddffd 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -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 > diff --git a/lib/Makefile b/lib/Makefile > index f545140ed9e7..4ee1ceae945a 100644 > --- a/lib/Makefile > +++ b/lib/Makefile > @@ -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 > > diff --git a/lib/fortify_kunit.c b/lib/fortify_kunit.c > new file mode 100644 > index 000000000000..4d7930b65107 > --- /dev/null > +++ b/lib/fortify_kunit.c > @@ -0,0 +1,77 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Runtime test cases for CONFIG_FORTIFY_SOURCE that aren't expected to > + * Oops th kernel on success. (For those, see drivers/misc/lkdtm/fortify.c) Nit: Oops _the_ kernel > + * > + * 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"); > -- > 2.34.1 >
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