On Thu, Jun 06, 2019 at 03:44:36PM -0300, Jason Gunthorpe wrote: > From: Jason Gunthorpe <jgg@xxxxxxxxxxxx> > > Trying to misuse a range outside its lifetime is a kernel bug. Use WARN_ON > and poison bytes to detect this condition. > > Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx> > Reviewed-by: Jérôme Glisse <jglisse@xxxxxxxxxx> > --- > v2 > - Keep range start/end valid after unregistration (Jerome) > --- > mm/hmm.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/mm/hmm.c b/mm/hmm.c > index 6802de7080d172..c2fecb3ecb11e1 100644 > --- a/mm/hmm.c > +++ b/mm/hmm.c > @@ -937,7 +937,7 @@ void hmm_range_unregister(struct hmm_range *range) > struct hmm *hmm = range->hmm; > > /* Sanity check this really should not happen. */ > - if (hmm == NULL || range->end <= range->start) > + if (WARN_ON(range->end <= range->start)) > return; > > mutex_lock(&hmm->lock); > @@ -948,7 +948,10 @@ void hmm_range_unregister(struct hmm_range *range) > range->valid = false; > mmput(hmm->mm); > hmm_put(hmm); > - range->hmm = NULL; > + > + /* The range is now invalid, leave it poisoned. */ > + range->valid = false; No need to set valid false again as you just did this 5 lines above. Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx> > + memset(&range->hmm, POISON_INUSE, sizeof(range->hmm)); > } > EXPORT_SYMBOL(hmm_range_unregister); > > -- > 2.21.0 >
