linux-hardening - [PATCH v2 03/21] KASAN: remove code paths guarded by CONFIG

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Date: Mon, 20 Nov 2023 19:34:14 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: David Rientjes <rientjes@...gle.com>, Christoph Lameter <cl@...ux.com>, 
 Pekka Enberg <penberg@...nel.org>, Joonsoo Kim <iamjoonsoo.kim@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
 Hyeonggon Yoo <42.hyeyoo@...il.com>, 
 Roman Gushchin <roman.gushchin@...ux.dev>, 
 Andrey Ryabinin <ryabinin.a.a@...il.com>, 
 Alexander Potapenko <glider@...gle.com>, 
 Andrey Konovalov <andreyknvl@...il.com>, Dmitry Vyukov <dvyukov@...gle.com>, 
 Vincenzo Frascino <vincenzo.frascino@....com>, 
 Marco Elver <elver@...gle.com>, Johannes Weiner <hannes@...xchg.org>, 
 Michal Hocko <mhocko@...nel.org>, Shakeel Butt <shakeelb@...gle.com>, 
 Muchun Song <muchun.song@...ux.dev>, Kees Cook <keescook@...omium.org>, 
 linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
 kasan-dev@...glegroups.com, cgroups@...r.kernel.org, 
 linux-hardening@...r.kernel.org, Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH v2 03/21] KASAN: remove code paths guarded by CONFIG_SLAB

With SLAB removed and SLUB the only remaining allocator, we can clean up
some code that was depending on the choice.

Reviewed-by: Kees Cook <keescook@...omium.org>
Reviewed-by: Marco Elver <elver@...gle.com>
Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/kasan/common.c     | 13 ++-----------
 mm/kasan/kasan.h      |  3 +--
 mm/kasan/quarantine.c |  7 -------
 3 files changed, 3 insertions(+), 20 deletions(-)

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 256930da578a..5d95219e69d7 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -153,10 +153,6 @@ void __kasan_poison_object_data(struct kmem_cache *cache, void *object)
  * 2. A cache might be SLAB_TYPESAFE_BY_RCU, which means objects can be
  *    accessed after being freed. We preassign tags for objects in these
  *    caches as well.
- * 3. For SLAB allocator we can't preassign tags randomly since the freelist
- *    is stored as an array of indexes instead of a linked list. Assign tags
- *    based on objects indexes, so that objects that are next to each other
- *    get different tags.
  */
 static inline u8 assign_tag(struct kmem_cache *cache,
 					const void *object, bool init)
@@ -171,17 +167,12 @@ static inline u8 assign_tag(struct kmem_cache *cache,
 	if (!cache->ctor && !(cache->flags & SLAB_TYPESAFE_BY_RCU))
 		return init ? KASAN_TAG_KERNEL : kasan_random_tag();
 
-	/* For caches that either have a constructor or SLAB_TYPESAFE_BY_RCU: */
-#ifdef CONFIG_SLAB
-	/* For SLAB assign tags based on the object index in the freelist. */
-	return (u8)obj_to_index(cache, virt_to_slab(object), (void *)object);
-#else
 	/*
-	 * For SLUB assign a random tag during slab creation, otherwise reuse
+	 * For caches that either have a constructor or SLAB_TYPESAFE_BY_RCU,
+	 * assign a random tag during slab creation, otherwise reuse
 	 * the already assigned tag.
 	 */
 	return init ? kasan_random_tag() : get_tag(object);
-#endif
 }
 
 void * __must_check __kasan_init_slab_obj(struct kmem_cache *cache,
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 8b06bab5c406..eef50233640a 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -373,8 +373,7 @@ void kasan_set_track(struct kasan_track *track, gfp_t flags);
 void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags);
 void kasan_save_free_info(struct kmem_cache *cache, void *object);
 
-#if defined(CONFIG_KASAN_GENERIC) && \
-	(defined(CONFIG_SLAB) || defined(CONFIG_SLUB))
+#ifdef CONFIG_KASAN_GENERIC
 bool kasan_quarantine_put(struct kmem_cache *cache, void *object);
 void kasan_quarantine_reduce(void);
 void kasan_quarantine_remove_cache(struct kmem_cache *cache);
diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
index ca4529156735..138c57b836f2 100644
--- a/mm/kasan/quarantine.c
+++ b/mm/kasan/quarantine.c
@@ -144,10 +144,6 @@ static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache)
 {
 	void *object = qlink_to_object(qlink, cache);
 	struct kasan_free_meta *meta = kasan_get_free_meta(cache, object);
-	unsigned long flags;
-
-	if (IS_ENABLED(CONFIG_SLAB))
-		local_irq_save(flags);
 
 	/*
 	 * If init_on_free is enabled and KASAN's free metadata is stored in
@@ -166,9 +162,6 @@ static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache)
 	*(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREE;
 
 	___cache_free(cache, object, _THIS_IP_);
-
-	if (IS_ENABLED(CONFIG_SLAB))
-		local_irq_restore(flags);
 }
 
 static void qlist_free_all(struct qlist_head *q, struct kmem_cache *cache)

-- 
2.42.1