Check the allocation size before toggling kfence_allocation_gate.
This way allocations that can't be served by KFENCE will not result in
waiting for another CONFIG_KFENCE_SAMPLE_INTERVAL without allocating
anything.
Suggested-by: Marco Elver <elver@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # 5.12+
Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
---
mm/kfence/core.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index d7666ace9d2e4..2623ff401a104 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -733,6 +733,13 @@ void kfence_shutdown_cache(struct kmem_cache *s)
void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags)
{
+ /*
+ * Perform size check before switching kfence_allocation_gate, so that
+ * we don't disable KFENCE without making an allocation.
+ */
+ if (size > PAGE_SIZE)
+ return NULL;
+
/*
* allocation_gate only needs to become non-zero, so it doesn't make
* sense to continue writing to it and pay the associated contention
@@ -757,9 +764,6 @@ void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags)
if (!READ_ONCE(kfence_enabled))
return NULL;
- if (size > PAGE_SIZE)
- return NULL;
-
return kfence_guarded_alloc(s, size, flags);
}
--
2.32.0.93.g670b81a890-goog
