[dm-devel] [PATCH 1/4] bcache: convert cached_dev.count from atomic_t to refcount_t

[Reshetova, Elena]

> On 10/20/2017 12:37 AM, Elena Reshetova 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 cached_dev.count is used as pure reference counter.
> > Convert it to refcount_t and fix up the operations.
> >
> > Suggested-by: Kees Cook <keescook at chromium.org>
> > Reviewed-by: David Windsor <dwindsor at gmail.com>
> > Reviewed-by: Hans Liljestrand <ishkamiel at gmail.com>
> > Signed-off-by: Elena Reshetova <elena.reshetova at intel.com>
> 
> Reviewed-by: Michael Lyle <mlyle at lyle.org>
> 
> Thanks for this-- I'm including it in my tree for possible inclusion in
> 4.15 (I've already sent my main chunk of changes upwards).

Thank you Mike! I am dropping then this patch from my list of maintained
conversions. 

Best Regards,
Elena.
> 
> Mike