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; + memset(&range->hmm, POISON_INUSE, sizeof(range->hmm)); } EXPORT_SYMBOL(hmm_range_unregister); -- 2.21.0
