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>
---
mm/hmm.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/mm/hmm.c b/mm/hmm.c
index 6c3b7398672c29..02752d3ef2ed92 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -936,8 +936,7 @@ EXPORT_SYMBOL(hmm_range_register);
*/
void hmm_range_unregister(struct hmm_range *range)
{
- /* Sanity check this really should not happen. */
- if (range->hmm == NULL || range->end <= range->start)
+ if (WARN_ON(range->end <= range->start))
return;
mutex_lock(&range->hmm->lock);
@@ -945,9 +944,13 @@ void hmm_range_unregister(struct hmm_range *range)
mutex_unlock(&range->hmm->lock);
/* Drop reference taken by hmm_range_register() */
- range->valid = false;
hmm_put(range->hmm);
- range->hmm = NULL;
+
+ /* The range is now invalid, leave it poisoned. */
+ range->valid = false;
+ range->start = ULONG_MAX;
+ range->end = 0;
+ memset(&range->hmm, POISON_INUSE, sizeof(range->hmm));
}
EXPORT_SYMBOL(hmm_range_unregister);
--
2.21.0
