On Wed, 30 Aug 2017, 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 futex_pi_state.refcount 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> Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
