Re: [PATCH v3 2/4] KUnit: KASAN Integration

[Patricia Alfonso]

On Thu, Apr 2, 2020 at 8:54 AM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote:
>
> On Wed, Apr 1, 2020 at 8:09 PM 'Patricia Alfonso' via kasan-dev
> <kasan-dev@xxxxxxxxxxxxxxxx> wrote:
> >
> > Integrate KASAN into KUnit testing framework.
> >         - Fail tests when KASAN reports an error that is not expected
> >         - Use KUNIT_EXPECT_KASAN_FAIL to expect a KASAN error in KASAN tests
> >         - Expected KASAN reports pass tests and are still printed when run
> >         without kunit_tool (kunit_tool still bypasses the report due to the
> >         test passing)
> >         - KUnit struct in current task used to keep track of the current test
> >         from KASAN code
> >
> > Make use of "[PATCH v3 kunit-next 1/2] kunit: generalize
> > kunit_resource API beyond allocated resources" and "[PATCH v3
> > kunit-next 2/2] kunit: add support for named resources" from Alan
> > Maguire [1]
> >         - A named resource is added to a test when a KASAN report is
> >          expected
> >         - This resource contains a struct for kasan_data containing
> >         booleans representing if a KASAN report is expected and if a
> >         KASAN report is found
> >
> > [1] (https://lore.kernel.org/linux-kselftest/1583251361-12748-1-git-send-email-alan.maguire@xxxxxxxxxx/T/#t)
> >
> > Signed-off-by: Patricia Alfonso <trishalfonso@xxxxxxxxxx>
> > ---
> >  include/kunit/test.h  |  5 +++++
> >  include/linux/kasan.h |  6 ++++++
> >  lib/kunit/test.c      | 13 ++++++++-----
> >  lib/test_kasan.c      | 37 +++++++++++++++++++++++++++++++++++++
> >  mm/kasan/report.c     | 33 +++++++++++++++++++++++++++++++++
> >  5 files changed, 89 insertions(+), 5 deletions(-)
> >
> > diff --git a/include/kunit/test.h b/include/kunit/test.h
> > index ac59d18e6bab..1dc3d118f64b 100644
> > --- a/include/kunit/test.h
> > +++ b/include/kunit/test.h
> > @@ -225,6 +225,11 @@ struct kunit {
> >         struct list_head resources; /* Protected by lock. */
> >  };
> >
> > +static inline void kunit_set_failure(struct kunit *test)
> > +{
> > +       WRITE_ONCE(test->success, false);
> > +}
> > +
> >  void kunit_init_test(struct kunit *test, const char *name, char *log);
> >
> >  int kunit_run_tests(struct kunit_suite *suite);
> > diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> > index 5cde9e7c2664..148eaef3e003 100644
> > --- a/include/linux/kasan.h
> > +++ b/include/linux/kasan.h
> > @@ -14,6 +14,12 @@ struct task_struct;
> >  #include <asm/kasan.h>
> >  #include <asm/pgtable.h>
> >
> > +/* kasan_data struct is used in KUnit tests for KASAN expected failures */
> > +struct kunit_kasan_expectation {
> > +       bool report_expected;
> > +       bool report_found;
> > +};
> > +
> >  extern unsigned char kasan_early_shadow_page[PAGE_SIZE];
> >  extern pte_t kasan_early_shadow_pte[PTRS_PER_PTE];
> >  extern pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD];
> > diff --git a/lib/kunit/test.c b/lib/kunit/test.c
> > index 2cb7c6220a00..030a3281591e 100644
> > --- a/lib/kunit/test.c
> > +++ b/lib/kunit/test.c
> > @@ -10,16 +10,12 @@
> >  #include <linux/kernel.h>
> >  #include <linux/kref.h>
> >  #include <linux/sched/debug.h>
> > +#include <linux/sched.h>
> >
> >  #include "debugfs.h"
> >  #include "string-stream.h"
> >  #include "try-catch-impl.h"
> >
> > -static void kunit_set_failure(struct kunit *test)
> > -{
> > -       WRITE_ONCE(test->success, false);
> > -}
> > -
> >  static void kunit_print_tap_version(void)
> >  {
> >         static bool kunit_has_printed_tap_version;
> > @@ -288,6 +284,10 @@ static void kunit_try_run_case(void *data)
> >         struct kunit_suite *suite = ctx->suite;
> >         struct kunit_case *test_case = ctx->test_case;
> >
> > +#if (IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_KUNIT))
> > +       current->kunit_test = test;
> > +#endif /* IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_KUNIT) */
> > +
> >         /*
> >          * kunit_run_case_internal may encounter a fatal error; if it does,
> >          * abort will be called, this thread will exit, and finally the parent
> > @@ -603,6 +603,9 @@ void kunit_cleanup(struct kunit *test)
> >                 spin_unlock(&test->lock);
> >                 kunit_remove_resource(test, res);
> >         }
> > +#if (IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_KUNIT))
> > +       current->kunit_test = NULL;
> > +#endif /* IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_KUNIT)*/
> >  }
> >  EXPORT_SYMBOL_GPL(kunit_cleanup);
> >
> > diff --git a/lib/test_kasan.c b/lib/test_kasan.c
> > index 3872d250ed2c..cf73c6bee81b 100644
> > --- a/lib/test_kasan.c
> > +++ b/lib/test_kasan.c
> > @@ -23,6 +23,43 @@
> >
> >  #include <asm/page.h>
> >
> > +#include <kunit/test.h>
> > +
> > +struct kunit_resource resource;
> > +struct kunit_kasan_expectation fail_data;
> > +
> > +#define KUNIT_SET_KASAN_DATA(test) do { \
> > +       fail_data.report_expected = true; \
> > +       fail_data.report_found = false; \
> > +       kunit_add_named_resource(test, \
> > +                               NULL, \
> > +                               NULL, \
> > +                               &resource, \
> > +                               "kasan_data", &fail_data); \
> > +} while (0)
> > +
> > +#define KUNIT_DO_EXPECT_KASAN_FAIL(test, condition) do { \
> > +       struct kunit_resource *resource; \
> > +       struct kunit_kasan_expectation *kasan_data; \
> > +       condition; \
> > +       resource = kunit_find_named_resource(test, "kasan_data"); \
> > +       kasan_data = resource->data; \
> > +       KUNIT_EXPECT_EQ(test, \
> > +                       kasan_data->report_expected, \
> > +                       kasan_data->report_found); \
> > +       kunit_put_resource(resource); \
> > +} while (0)
> > +
> > +/**
> > + * KUNIT_EXPECT_KASAN_FAIL() - Causes a test failure when the expression does
> > + * not cause a KASAN error.
> > + *
> > + */
> > +#define KUNIT_EXPECT_KASAN_FAIL(test, condition) do { \
> > +       KUNIT_SET_KASAN_DATA(test); \
> > +       KUNIT_DO_EXPECT_KASAN_FAIL(test, condition); \
> > +} while (0)
>
> Any reason to split this macro into two parts? Do we call any of them
> separately?
>
They are not called anywhere else... honestly, it was just a style
choice to make it clear that there are 2 parts to the expectation. I
don't think they have to be split if there's enough reason to smash
them together.

> > +
> >  /*
> >   * Note: test functions are marked noinline so that their names appear in
> >   * reports.
> > diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> > index 5ef9f24f566b..87330ef3a99a 100644
> > --- a/mm/kasan/report.c
> > +++ b/mm/kasan/report.c
> > @@ -32,6 +32,8 @@
> >
> >  #include <asm/sections.h>
> >
> > +#include <kunit/test.h>
> > +
> >  #include "kasan.h"
> >  #include "../slab.h"
> >
> > @@ -455,12 +457,38 @@ static bool report_enabled(void)
> >         return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
> >  }
> >
> > +#if IS_ENABLED(CONFIG_KUNIT)
> > +void kasan_update_kunit_status(struct kunit *cur_test)
> > +{
> > +       struct kunit_resource *resource;
> > +       struct kunit_kasan_expectation *kasan_data;
> > +
> > +       if (kunit_find_named_resource(cur_test, "kasan_data")) {
> > +               resource = kunit_find_named_resource(cur_test, "kasan_data");
> > +               kasan_data = resource->data;
> > +               kasan_data->report_found = true;
> > +
> > +               if (!kasan_data->report_expected)
> > +                       kunit_set_failure(current->kunit_test);
>
> Hm, we only call KUNIT_SET_KASAN_DATA() for KASAN tests that we expect
> to fail AFAICS. Then we end up calling kunit_set_failure twice, once
> here and the other time when we do KUNIT_EXPECT_EQ() in
> KUNIT_DO_EXPECT_KASAN_FAIL(). Or maybe there's something I
> misunderstand.
>

You are right. I didn't realize, but yes. If the report_expected is
false, KUNIT_DO_EXPECT_KASAN_FAIL() will set the test failure in
KUNIT_EXPECT_EQ(). I think this is just leftover logic from before I
thought to use KUNIT_EXPECT_EQ().

> > +               else
> > +                       return;
>
> Nit: "else return;" can be dropped.
>
> You can actually reorder the code a bit to make it easier to read:
>
> if (!kunit_find_named_resource(cur_test, "kasan_data")) {
>   kunit_set_failure(current->kunit_test);
>   return;
> }
> // here comes kasan tests checks
>

I agree. This looks much cleaner. The thing to note is that anyone can
add a named resource to a test. I doubt anyone will name their
resource "kasan_data" outside of this file, but it may be worth adding
a comment advising against it.

>
>
>
>
> > +       } else
> > +               kunit_set_failure(current->kunit_test);
> > +}
> > +#endif /* IS_ENABLED(CONFIG_KUNIT) */
> > +
> >  void kasan_report_invalid_free(void *object, unsigned long ip)
> >  {
> >         unsigned long flags;
> >         u8 tag = get_tag(object);
> >
> >         object = reset_tag(object);
> > +
> > +#if IS_ENABLED(CONFIG_KUNIT)
> > +       if (current->kunit_test)
> > +               kasan_update_kunit_status(current->kunit_test);
> > +#endif /* IS_ENABLED(CONFIG_KUNIT) */
> > +
> >         start_report(&flags);
> >         pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
> >         print_tags(tag, object);
> > @@ -481,6 +509,11 @@ void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned lon
> >         if (likely(!report_enabled()))
> >                 return;
> >
> > +#if IS_ENABLED(CONFIG_KUNIT)
> > +       if (current->kunit_test)
> > +               kasan_update_kunit_status(current->kunit_test);
> > +#endif /* IS_ENABLED(CONFIG_KUNIT) */
> > +
> >         disable_trace_on_warning();
> >
> >         tagged_addr = (void *)addr;
> > --

Thanks for the comments!

Best,
Patricia