On 6/6/19 11:44 AM, 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>
Reviewed-by: Ralph Campbell <rcampbell@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;
WARN_ON() is definitely better than silent return but I wonder how
useful it is since the caller shouldn't be modifying the hmm_range
once it is registered. Other fields could be changed too...
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);
