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

[Brendan Higgins]

On Thu, Feb 27, 2020 at 6:04 AM Alan Maguire <alan.maguire@xxxxxxxxxx> wrote:

Sorry for the delay in reviews. I have been preoccupied by some Google
internal stuff.

> On Wed, 26 Feb 2020, Patricia Alfonso wrote:
>
> > Integrate KASAN into KUnit testing framework.
>
> This is a great idea! Some comments/suggestions below...
>
> >  - Fail tests when KASAN reports an error that is not expected
> >  - Use KUNIT_EXPECT_KASAN_FAIL to expect a KASAN error in KASAN tests
> >  - KUnit struct added to current task to keep track of the current test
> > from KASAN code
> >  - Booleans representing if a KASAN report is expected and if a KASAN
> >  report is found added to kunit struct
> >  - This prints "line# has passed" or "line# has failed"
> >
> > Signed-off-by: Patricia Alfonso <trishalfonso@xxxxxxxxxx>
> > ---
> > If anyone has any suggestions on how best to print the failure
> > messages, please share!
> >
> > One issue I have found while testing this is the allocation fails in
> > kmalloc_pagealloc_oob_right() sometimes, but not consistently. This
> > does cause the test to fail on the KUnit side, as expected, but it
> > seems to skip all the tests before this one because the output starts
> > with this failure instead of with the first test, kmalloc_oob_right().
> >
> >  include/kunit/test.h                | 24 ++++++++++++++++++++++++
> >  include/linux/sched.h               |  7 ++++++-
> >  lib/kunit/test.c                    |  7 ++++++-
> >  mm/kasan/report.c                   | 19 +++++++++++++++++++
> >  tools/testing/kunit/kunit_kernel.py |  2 +-
> >  5 files changed, 56 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/kunit/test.h b/include/kunit/test.h
> > index 2dfb550c6723..2e388f8937f3 100644
> > --- a/include/kunit/test.h
> > +++ b/include/kunit/test.h
> > @@ -21,6 +21,8 @@ struct kunit_resource;
> >  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);
> > +
> >  /**
> >   * struct kunit_resource - represents a *test managed resource*
> >   * @allocation: for the user to store arbitrary data.
> > @@ -191,6 +193,9 @@ struct kunit {
> >        * protect it with some type of lock.
> >        */
> >       struct list_head resources; /* Protected by lock. */
> > +
> > +     bool kasan_report_expected;
> > +     bool kasan_report_found;
> >  };
> >
>
> Is this needed here? You're testing something pretty
> specific so it seems wrong to add to the generic
> kunit resource unless there's a good reason. I see the
> code around setting these values in mm/kasan/report.c,
> but I wonder if we could do something more generic.
>
> How about the concept of a static resource (assuming a
> dynamically allocated one is out because it messes
> with memory allocation tests)? Something like this:
>
> #define kunit_add_static_resource(test, resource_ptr, resource_field)   \
>         do {                                                            \
>                 spin_lock(&test->lock);                                 \
>                 (resource_ptr)->resource_field.init = NULL;             \
>                 (resource_ptr)->resource_field.free = NULL;             \
>                 list_add_tail(&(resource_ptr)->resource_field,          \
>                               &test->resources);                        \
>                 spin_unlock(&test->lock);                               \
>         } while (0)
>
>
> Within your kasan code you could then create a kasan-specific
> structure that embends a kunit_resource, and contains the
> values you need:
>
> struct kasan_report_resource {
>         struct kunit_resource res;
>         bool kasan_report_expected;
>         bool kasan_report_found;
> };
>
> (One thing we'd need to do for such static resources is fix
> kunit_resource_free() to check if there's a free() function,
> and if not assume a static resource)
>
> If you then create an init() function associated with your
> kunit suite (which will be run for every case) it can do this:
>
> int kunit_kasan_test_init(struct kunit *test)
> {
>         kunit_add_static_resource(test, &my_kasan_report_resource, res);
>         ...
> }
>
> The above should also be used to initialize current->kasan_unit_test
> instead of doing that in kunit_try_run_case().  With those
> changes, you don't (I think) need to change anything in core
> kunit (assuming support for static resources).
>
> To retrieve the resource during tests or in kasan context, the
> method seems to be to use kunit_resource_find(). However, that
> requires a match function which seems a bit heavyweight for the
> static case.  We should probably have a default "find by name"
> or similar function here, and add an optional "name" field
> to kunit resources to simplify things.  Anyway here you'd
> use something like:
>
>         kasan_report_resource = kunit_resource_find(test, matchfn,
>                                                     NULL, matchdata);
>
>
> Are there any barriers to taking this sort of approach (apart
> from the support for static resources not being there yet)?

This is a really interesting idea, Alan! I never imagined
kunit_resources being used this way, and I like it. I saw you sent
some patches to implement this stuff, so I will withhold further
comments on that here.