Re: [RFC PATCH v2 2/3] KUnit: KASAN Integration

[Patricia Alfonso]

On Tue, Mar 24, 2020 at 9:45 AM Alan Maguire <alan.maguire@xxxxxxxxxx> wrote:
>
>
> On Thu, 19 Mar 2020, Patricia Alfonso 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 "[RFC PATCH kunit-next 1/2] kunit: generalize
> > kunit_resource API beyond allocated resources" and "[RFC PATCH
> > 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 | 10 ++++++++++
> >  lib/kunit/test.c     | 10 +++++++++-
> >  lib/test_kasan.c     | 37 +++++++++++++++++++++++++++++++++++++
> >  mm/kasan/report.c    | 33 +++++++++++++++++++++++++++++++++
> >  4 files changed, 89 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/kunit/test.h b/include/kunit/test.h
> > index 70ee581b19cd..2ab265f4f76c 100644
> > --- a/include/kunit/test.h
> > +++ b/include/kunit/test.h
> > @@ -19,9 +19,19 @@
> >
> >  struct kunit_resource;
> >
> > +#ifdef CONFIG_KASAN
> > +/* kasan_data struct is used in KUnit tests for KASAN expected failures */
> > +struct kunit_kasan_expectation {
> > +     bool report_expected;
> > +     bool report_found;
> > +};
> > +#endif /* CONFIG_KASAN */
> > +
>
> Above should be moved to mm/kasan/kasan.h I think.
>
> >  typedef int (*kunit_resource_init_t)(struct kunit_resource *, void *);
> >  typedef void (*kunit_resource_free_t)(struct kunit_resource *);
> >
> > +void kunit_set_failure(struct kunit *test);
> > +
>
> Can you explain a bit more about why we need this exported?
> I see where it's used but I'd just like to make sure I
> understand what you're trying to do. Thanks!
>
I need the ability to set a KUnit test failure from outside the KUnit
code so that a test that does not expect a KASAN failure, but reaches
the point in the KASAN code where a report is printed will properly
fail due to this found KASAN failure.

> >  /**
> >   * struct kunit_resource - represents a *test managed resource*
> >   * @data: for the user to store arbitrary data.
> > diff --git a/lib/kunit/test.c b/lib/kunit/test.c
> > index 86a4d9ca0a45..3f927ef45827 100644
> > --- a/lib/kunit/test.c
> > +++ b/lib/kunit/test.c
> > @@ -10,11 +10,12 @@
> >  #include <linux/kernel.h>
> >  #include <linux/kref.h>
> >  #include <linux/sched/debug.h>
> > +#include <linux/sched.h>
> >
> >  #include "string-stream.h"
> >  #include "try-catch-impl.h"
> >
> > -static void kunit_set_failure(struct kunit *test)
> > +void kunit_set_failure(struct kunit *test)
> >  {
> >       WRITE_ONCE(test->success, false);
> >  }
> > @@ -237,6 +238,10 @@ 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_BUILTIN(CONFIG_KUNIT))
> > +     current->kunit_test = test;
> > +#endif /* IS_ENABLED(CONFIG_KASAN) && IS_BUILTIN(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
> > @@ -590,6 +595,9 @@ void kunit_cleanup(struct kunit *test)
> >               spin_unlock(&test->lock);
> >               kunit_remove_resource(test, res);
> >       }
> > +#if (IS_ENABLED(CONFIG_KASAN) && IS_BUILTIN(CONFIG_KUNIT))
> > +     current->kunit_test = NULL;
>
> As per patch 1, I'd suggest changing here and elsewhere to
> "IS_ENABLED(CONFIG_KUNIT)".
>
"IS_ENABLED(CONFIG_KUNIT)" does not work because KASAN is built-in so
it can't rely on modules so this patchset relies on KUnit being
built-in.

> > +#endif /* IS_ENABLED(CONFIG_KASAN) && IS_BUILTIN(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)
> > +
> >  /*
> >   * 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..ef3d0f54097e 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_BUILTIN(CONFIG_KUNIT)
>
> again we could tweak this to IS_ENABLED(CONFIG_KUNIT); BTW
> the reason we can compile kunit as a module for these tests
> is the KASAN tests are tristate themselves. If they were
> builtin only it wouldn't be possible to build kunit as
> a module.
>
> > +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);
> > +             else
> > +                     return;
> > +     } else
> > +             kunit_set_failure(current->kunit_test);
> > +}
> > +#endif /* IS_BUILTIN(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_BUILTIN(CONFIG_KUNIT)
>
> same comment as above.
>
> > +     if (current->kunit_test)
> > +             kasan_update_kunit_status(current->kunit_test);
> > +#endif /* IS_BUILTIN(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_BUILTIN(CONFIG_KUNIT)
>
> here too.
>
> > +     if (current->kunit_test)
> > +             kasan_update_kunit_status(current->kunit_test);
> > +#endif /* IS_BUILTIN(CONFIG_KUNIT) */
> > +
> >       disable_trace_on_warning();
> >
> >       tagged_addr = (void *)addr;
> > --
> > 2.25.1.696.g5e7596f4ac-goog
> >
> >

-- 
Best,
Patricia