mm: fix wrong kasan report [1/1]

PD#SWPL-13281

Problem:
There are 2 types of wrong kasan report after merge change of
save wasted slab.
1, slab-out-of-bounds, which is caused by krealloc set shadow
   memory out-of-range, since tail of page was freed.
2, use-after-free, which is caused by kasan_free_pages called
   after a page freed. Because this function already called in
   free_page, so it marked shadow memory twice.

Solution:
1, make shadow do not out of range if a tail page was freed and
   been realloc again.
2, remove call of kasan_free_pages.

Verify:
X301

Change-Id: Ib5bdcbb618a783920009bb97d112c361888b0d7c
Signed-off-by: Tao Zeng <tao.zeng@amlogic.com>

4 files changed, 24 insertions, 2 deletions

diff --git a/drivers/amlogic/memory_ext/Kconfig b/drivers/amlogic/memory_ext/Kconfig
index 8bb640e..0da0422 100644
--- a/drivers/amlogic/memory_ext/Kconfig
+++ b/drivers/amlogic/memory_ext/Kconfig
@@ -55,7 +55,6 @@ config AMLOGIC_KASAN32
 config AMLOGIC_VMAP
 	bool "Amlogic kernel stack"
 	depends on AMLOGIC_MEMORY_EXTEND
-	depends on !KASAN
 	default y
 	help
 		This config is used to enable amlogic kernel stack
diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 35408ec..55cd682 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -641,6 +641,11 @@ void kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
 	redzone_start = round_up((unsigned long)(ptr + size),
 				KASAN_SHADOW_SCALE_SIZE);
 	redzone_end = (unsigned long)ptr + (PAGE_SIZE << compound_order(page));
+#ifdef CONFIG_AMLOGIC_MEMORY_EXTEND
+	if (PageOwnerPriv1(page)) { /* end of this page was freed */
+		redzone_end = (unsigned long)ptr + PAGE_ALIGN(size);
+	}
+#endif
 
 	kasan_unpoison_shadow(ptr, size);
 	kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b453904..9c45a55 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -931,7 +931,17 @@ done_merging:
 		}
 	}
 
+#if defined(CONFIG_AMLOGIC_MEMORY_EXTEND) && defined(CONFIG_KASAN)
+	/*
+	 * always put freed page to tail of buddy system, in
+	 * order to increase probability of use-after-free
+	 * for KASAN check.
+	 */
+	list_add_tail(&page->lru,
+		      &zone->free_area[order].free_list[migratetype]);
+#else
 	list_add(&page->lru, &zone->free_area[order].free_list[migratetype]);
+#endif
 out:
 	zone->free_area[order].nr_free++;
 #ifdef CONFIG_AMLOGIC_MEMORY_EXTEND
@@ -2622,10 +2632,19 @@ void free_hot_cold_page(struct page *page, bool cold)
 	}
 
 	pcp = &this_cpu_ptr(zone->pageset)->pcp;
+#if defined(CONFIG_AMLOGIC_MEMORY_EXTEND) && defined(CONFIG_KASAN)
+	/*
+	 * always put freed page to tail of buddy system, in
+	 * order to increase probability of use-after-free
+	 * for KASAN check.
+	 */
+	list_add_tail(&page->lru, &pcp->lists[migratetype]);
+#else
 	if (!cold)
 		list_add(&page->lru, &pcp->lists[migratetype]);
 	else
 		list_add_tail(&page->lru, &pcp->lists[migratetype]);
+#endif
 	pcp->count++;
 	if (pcp->count >= pcp->high) {
 		unsigned long batch = READ_ONCE(pcp->batch);
diff --git a/mm/slub.c b/mm/slub.c
index 59ec527..7dfc2a4 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3734,7 +3734,6 @@ static void aml_slub_free_large(struct page *page, const void *obj)
 			__func__, page_address(page), nr_pages, obj);
 		for (i = 0; i < nr_pages; i++)  {
 			__free_pages(page, 0);
-			kasan_free_pages(page, 0);
 			page++;
 		}
 	}