mm/mempool.c: kasan: poison mempool elements

Mempools keep allocated objects in reserved for situations when ordinary
allocation may not be possible to satisfy.  These objects shouldn't be
accessed before they leave the pool.

This patch poison elements when get into the pool and unpoison when they
leave it.  This will let KASan to detect use-after-free of mempool's
elements.

Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Tested-by: David Rientjes <rientjes@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Chernenkov <drcheren@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 36 insertions, 0 deletions

diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 936d816..6c513a6 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -389,6 +389,19 @@ void kasan_krealloc(const void *object, size_t size)
 		kasan_kmalloc(page->slab_cache, object, size);
 }
 
+void kasan_kfree(void *ptr)
+{
+	struct page *page;
+
+	page = virt_to_head_page(ptr);
+
+	if (unlikely(!PageSlab(page)))
+		kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
+				KASAN_FREE_PAGE);
+	else
+		kasan_slab_free(page->slab_cache, ptr);
+}
+
 void kasan_kfree_large(const void *ptr)
 {
 	struct page *page = virt_to_page(ptr);
diff --git a/mm/mempool.c b/mm/mempool.c
index 2884d5b..2cc08de 100644
--- a/mm/mempool.c
+++ b/mm/mempool.c
@@ -12,6 +12,7 @@
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/highmem.h>
+#include <linux/kasan.h>
 #include <linux/kmemleak.h>
 #include <linux/export.h>
 #include <linux/mempool.h>
@@ -101,10 +102,31 @@ static inline void poison_element(mempool_t *pool, void *element)
 }
 #endif /* CONFIG_DEBUG_SLAB || CONFIG_SLUB_DEBUG_ON */
 
+static void kasan_poison_element(mempool_t *pool, void *element)
+{
+	if (pool->alloc == mempool_alloc_slab)
+		kasan_slab_free(pool->pool_data, element);
+	if (pool->alloc == mempool_kmalloc)
+		kasan_kfree(element);
+	if (pool->alloc == mempool_alloc_pages)
+		kasan_free_pages(element, (unsigned long)pool->pool_data);
+}
+
+static void kasan_unpoison_element(mempool_t *pool, void *element)
+{
+	if (pool->alloc == mempool_alloc_slab)
+		kasan_slab_alloc(pool->pool_data, element);
+	if (pool->alloc == mempool_kmalloc)
+		kasan_krealloc(element, (size_t)pool->pool_data);
+	if (pool->alloc == mempool_alloc_pages)
+		kasan_alloc_pages(element, (unsigned long)pool->pool_data);
+}
+
 static void add_element(mempool_t *pool, void *element)
 {
 	BUG_ON(pool->curr_nr >= pool->min_nr);
 	poison_element(pool, element);
+	kasan_poison_element(pool, element);
 	pool->elements[pool->curr_nr++] = element;
 }
 
@@ -114,6 +136,7 @@ static void *remove_element(mempool_t *pool)
 
 	BUG_ON(pool->curr_nr < 0);
 	check_element(pool, element);
+	kasan_unpoison_element(pool, element);
 	return element;
 }