> On Apr 22, 2019, at 11:07 AM, Cong Wang <xiyou.wangc...@gmail.com> wrote: > > On Mon, Apr 22, 2019 at 11:04 AM Cong Wang <xiyou.wangc...@gmail.com> wrote: >> >> On Fri, Apr 19, 2019 at 6:06 PM Andre Guedes <andre.gue...@intel.com> wrote: >>> >>> If 'entry' is NULL we WARN_ON() but dereference the pointer anyway, >>> generating a null pointer dereference bug. This patch fixes should_ >>> restart_cycle() so we return if the pointer is NULL. >> >> Hmm, while you are on it, how is it possible to have entry==NULL >> for should_restart_cycle(). It is only called in advance_sched() >> where entry is already checked against NULL right before it, >> so for me, entry is always NULL at the point of calling >> should_restart_cycle(). > > I meant, 'entry' is always non-NULL here... I typed too fast.
Your assessment is correct. I believe the WARN_ON() was added as a defensive practice to prevent null pointer dereference in case someone misuse that helper in the future. - Andre
