RE: [PATCH 1/3] [S390] vmur: convert urdev.ref_count from atomic_t to refcount_t

[Reshetova, Elena]

> On Fri, 20 Oct 2017 10:47:48 +0300
> Elena Reshetova <elena.reshetova@xxxxxxxxx> wrote:
> 
> > atomic_t variables are currently used to implement reference
> > counters with the following properties:
> >  - counter is initialized to 1 using atomic_set()
> >  - a resource is freed upon counter reaching zero
> >  - once counter reaches zero, its further
> >    increments aren't allowed
> >  - counter schema uses basic atomic operations
> >    (set, inc, inc_not_zero, dec_and_test, etc.)
> >
> > Such atomic variables should be converted to a newly provided
> > refcount_t type and API that prevents accidental counter overflows
> > and underflows. This is important since overflows and underflows
> > can lead to use-after-free situation and be exploitable.
> >
> > The variable urdev.ref_count is used as pure reference counter.
> > Convert it to refcount_t and fix up the operations.
> >
> > Suggested-by: Kees Cook <keescook@xxxxxxxxxxxx>
> > Reviewed-by: David Windsor <dwindsor@xxxxxxxxx>
> > Reviewed-by: Hans Liljestrand <ishkamiel@xxxxxxxxx>
> > Signed-off-by: Elena Reshetova <elena.reshetova@xxxxxxxxx>
> 
> Added to s390/linux:features for the next merge window. Thanks.

Thank you very much!

Best Regards,
Elena.
> 
> --
> blue skies,
>    Martin.
> 
> "Reality continues to ruin my life." - Calvin.