Re: [PATCH v4 2/4] KUnit: KASAN Integration

[Andrey Konovalov <andreyknvl@google.com>]

On Fri, Apr 3, 2020 at 7:17 PM Patricia Alfonso <trishalfonso@google.com> wrote:
>
> On Fri, Apr 3, 2020 at 6:20 AM Andrey Konovalov <andreyknvl@google.com> wrote:
> >
> > On Thu, Apr 2, 2020 at 10:46 PM 'Patricia Alfonso' via kasan-dev
> > <kasan-dev@googlegroups.com> 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@oracle.com/T/#t)
> > >
> > > Signed-off-by: Patricia Alfonso <trishalfonso@google.com>
> > > Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
> > > ---
> > >  include/kunit/test.h  |  5 ++++
> > >  include/linux/kasan.h |  6 +++++
> > >  lib/kunit/test.c      | 13 ++++++----
> > >  lib/test_kasan.c      | 56 +++++++++++++++++++++++++++++++++++++++----
> > >  mm/kasan/report.c     | 30 +++++++++++++++++++++++
> > >  5 files changed, 101 insertions(+), 9 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..dbfa0875ee09 100644
> > > --- a/lib/test_kasan.c
> > > +++ b/lib/test_kasan.c
> > > @@ -23,12 +23,60 @@
> > >
> > >  #include <asm/page.h>
> > >
> > > -/*
> > > - * Note: test functions are marked noinline so that their names appear in
> > > - * reports.
> > > +#include <kunit/test.h>
> > > +
> > > +static struct kunit_resource resource;
> > > +static struct kunit_kasan_expectation fail_data;
> > > +static bool multishot;
> > > +static int orig_panic_on_warn;
> > > +
> > > +static int kasan_test_init(struct kunit *test)
> > > +{
> > > +       /*
> > > +        * Temporarily enable multi-shot mode and set panic_on_warn=0.
> > > +        * Otherwise, we'd only get a report for the first case.
> > > +        */
> > > +       multishot = kasan_save_enable_multi_shot();
> > > +
> > > +       orig_panic_on_warn = panic_on_warn;
> > > +       panic_on_warn = 0;
> > > +
> > > +       return 0;
> > > +}
> > > +
> > > +static void kasan_test_exit(struct kunit *test)
> > > +{
> > > +       kasan_restore_multi_shot(multishot);
> > > +
> > > +       /* Restore panic_on_warn */
> >
> > Nit: no need for this comment, I think it's clear that here we're
> > restoring stuff we saved in kasan_test_init().
> >
> Okay!
>
> > > +       panic_on_warn = orig_panic_on_warn;
> > > +}
> > > +
> > > +/**
> > > + * KUNIT_EXPECT_KASAN_FAIL() - Causes a test failure when the expression does
> > > + * not cause a KASAN error. This uses a KUnit resource named "kasan_data." Do
> > > + * Do not use this name for a KUnit resource outside here.
> > > + *
> > >   */
> > > +#define KUNIT_EXPECT_KASAN_FAIL(test, condition) do { \
> > > +       struct kunit_resource *res; \
> > > +       struct kunit_kasan_expectation *kasan_data; \
> > > +       fail_data.report_expected = true; \
> > > +       fail_data.report_found = false; \
> > > +       kunit_add_named_resource(test, \
> > > +                               NULL, \
> > > +                               NULL, \
> > > +                               &resource, \
> > > +                               "kasan_data", &fail_data); \
> > > +       condition; \
> > > +       res = kunit_find_named_resource(test, "kasan_data"); \
> >
> > Is res going to be == &resource here? If so, no need to call
> > kunit_find_named_resource().
> >
>
> You're right. Thanks for the suggestion!
>
> > > +       kasan_data = res->data; \
> > > +       KUNIT_EXPECT_EQ(test, \
> > > +                       kasan_data->report_expected, \
> > > +                       kasan_data->report_found); \
> >
> > Nit: no need to add kasan_data var, just use resource.data->report_expected.
> >
>
> I can probably just use fail_data->report_expected, actually.
>
> > > +       kunit_put_resource(res); \
> > > +} while (0)
> > >
> > > -static noinline void __init kmalloc_oob_right(void)
> > >  {
> > >         char *ptr;
> > >         size_t size = 123;
> > > diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> > > index 5ef9f24f566b..497477c4b679 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 +457,35 @@ 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)
> >
> > This isn't used outside of report.c, right? Then _static_ void
> > kasan_update_kunit_status().
> >
>
> Correct.
>
> > > +{
> > > +       struct kunit_resource *resource;
> > > +       struct kunit_kasan_expectation *kasan_data;
> > > +
> > > +       if (!kunit_find_named_resource(cur_test, "kasan_data")) {
> > > +               kunit_set_failure(cur_test);
> > > +               return;
> > > +       }
> > > +
> > > +       resource = kunit_find_named_resource(cur_test, "kasan_data");
> >
> > Do this before the if above, and then check if (!resource), will save
> > you a call to kunit_find_named_resource().
> >
> > > +       kasan_data = resource->data;
> > > +       kasan_data->report_found = true;
> >
> > No need for kasan_data var (if it can't be NULL or something), just do:
> >
> > resource->data->report_found = true;
> >
>
> The compiler seems to really hate this...
> mm/kasan/report.c: In function ‘kasan_update_kunit_status’:
> mm/kasan/report.c:471:16: warning: dereferencing ‘void *’ pointer
>   471 |  resource->data->report_found = true;
>       |                ^~
> mm/kasan/report.c:471:16: error: request for member ‘report_found’ in
> something not a structure or union
>
> Do you know how to fix this? I don't think I fully understand the error.

Ah, resource->data is a void *, missed that. Let's keep the kasan_data
var then, but do explicit casting:

kasan_data = (struct kunit_kasan_expectation *)resource->data;
kasan_data->report_found = true;

>
> > > +}
> > > +#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 +506,11 @@ 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;
>
> --
> Best,
> Patricia