mm: kfence: fix objcgs vector allocation

If the kfence object is allocated to be used for objects vector, then
this slot of the pool eventually being occupied permanently since the
vector is never freed.  The solutions could be (1) freeing vector when
the kfence object is freed or (2) allocating all vectors statically.

Since the memory consumption of object vectors is low, it is better to
chose (2) to fix the issue and it is also can reduce overhead of vectors
allocating in the future.

Link: https://lkml.kernel.org/r/20220328132843.16624-1-songmuchun@bytedance.com
Fixes: d3fb45f370d9 ("mm, kfence: insert KFENCE hooks for SLAB")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 13 insertions, 1 deletions

diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index 2f9fdfde1941..a203747ad2c0 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -566,6 +566,8 @@ static unsigned long kfence_init_pool(void)
 	 * enters __slab_free() slow-path.
 	 */
 	for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) {
+		struct slab *slab = page_slab(&pages[i]);
+
 		if (!i || (i % 2))
 			continue;
 
@@ -573,7 +575,11 @@ static unsigned long kfence_init_pool(void)
 		if (WARN_ON(compound_head(&pages[i]) != &pages[i]))
 			return addr;
 
-		__SetPageSlab(&pages[i]);
+		__folio_set_slab(slab_folio(slab));
+#ifdef CONFIG_MEMCG
+		slab->memcg_data = (unsigned long)&kfence_metadata[i / 2 - 1].objcg |
+				   MEMCG_DATA_OBJCGS;
+#endif
 	}
 
 	/*
@@ -1033,6 +1039,9 @@ void __kfence_free(void *addr)
 {
 	struct kfence_metadata *meta = addr_to_metadata((unsigned long)addr);
 
+#ifdef CONFIG_MEMCG
+	KFENCE_WARN_ON(meta->objcg);
+#endif
 	/*
 	 * If the objects of the cache are SLAB_TYPESAFE_BY_RCU, defer freeing
 	 * the object, as the object page may be recycled for other-typed
diff --git a/mm/kfence/kfence.h b/mm/kfence/kfence.h
index 2a2d5de9d379..9a6c4b1b12a8 100644
--- a/mm/kfence/kfence.h
+++ b/mm/kfence/kfence.h
@@ -89,6 +89,9 @@ struct kfence_metadata {
 	struct kfence_track free_track;
 	/* For updating alloc_covered on frees. */
 	u32 alloc_stack_hash;
+#ifdef CONFIG_MEMCG
+	struct obj_cgroup *objcg;
+#endif
 };
 
 extern struct kfence_metadata kfence_metadata[CONFIG_KFENCE_NUM_OBJECTS];