[PATCH v2 3/4] mm/slab: Refactor common ksize KASAN logic into slab_common.c

[Marco Elver]

This refactors common code of ksize() between the various allocators
into slab_common.c: __ksize() is the allocator-specific implementation
without instrumentation, whereas ksize() includes the required KASAN
logic.

Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: kasan-dev@xxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
---
 include/linux/slab.h |  1 +
 mm/slab.c            | 28 ++++++----------------------
 mm/slab_common.c     | 26 ++++++++++++++++++++++++++
 mm/slob.c            |  4 ++--
 mm/slub.c            | 14 ++------------
 5 files changed, 37 insertions(+), 36 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 9449b19c5f10..98c3d12b7275 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -184,6 +184,7 @@ void * __must_check __krealloc(const void *, size_t, gfp_t);
 void * __must_check krealloc(const void *, size_t, gfp_t);
 void kfree(const void *);
 void kzfree(const void *);
+size_t __ksize(const void *);
 size_t ksize(const void *);
 
 #ifdef CONFIG_HAVE_HARDENED_USERCOPY_ALLOCATOR
diff --git a/mm/slab.c b/mm/slab.c
index f7117ad9b3a3..394e7c7a285e 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -4204,33 +4204,17 @@ void __check_heap_object(const void *ptr, unsigned long n, struct page *page,
 #endif /* CONFIG_HARDENED_USERCOPY */
 
 /**
- * ksize - get the actual amount of memory allocated for a given object
- * @objp: Pointer to the object
+ * __ksize -- Uninstrumented ksize.
  *
- * kmalloc may internally round up allocations and return more memory
- * than requested. ksize() can be used to determine the actual amount of
- * memory allocated. The caller may use this additional memory, even though
- * a smaller amount of memory was initially specified with the kmalloc call.
- * The caller must guarantee that objp points to a valid object previously
- * allocated with either kmalloc() or kmem_cache_alloc(). The object
- * must not be freed during the duration of the call.
- *
- * Return: size of the actual memory used by @objp in bytes
+ * Unlike ksize(), __ksize() is uninstrumented, and does not provide the same
+ * safety checks as ksize() with KASAN instrumentation enabled.
  */
-size_t ksize(const void *objp)
+size_t __ksize(const void *objp)
 {
-	size_t size;
-
 	BUG_ON(!objp);
 	if (unlikely(objp == ZERO_SIZE_PTR))
 		return 0;
 
-	size = virt_to_cache(objp)->object_size;
-	/* We assume that ksize callers could use the whole allocated area,
-	 * so we need to unpoison this area.
-	 */
-	kasan_unpoison_shadow(objp, size);
-
-	return size;
+	return virt_to_cache(objp)->object_size;
 }
-EXPORT_SYMBOL(ksize);
+EXPORT_SYMBOL(__ksize);
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 58251ba63e4a..b7c6a40e436a 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1597,6 +1597,32 @@ void kzfree(const void *p)
 }
 EXPORT_SYMBOL(kzfree);
 
+/**
+ * ksize - get the actual amount of memory allocated for a given object
+ * @objp: Pointer to the object
+ *
+ * kmalloc may internally round up allocations and return more memory
+ * than requested. ksize() can be used to determine the actual amount of
+ * memory allocated. The caller may use this additional memory, even though
+ * a smaller amount of memory was initially specified with the kmalloc call.
+ * The caller must guarantee that objp points to a valid object previously
+ * allocated with either kmalloc() or kmem_cache_alloc(). The object
+ * must not be freed during the duration of the call.
+ *
+ * Return: size of the actual memory used by @objp in bytes
+ */
+size_t ksize(const void *objp)
+{
+	size_t size = __ksize(objp);
+	/*
+	 * We assume that ksize callers could use whole allocated area,
+	 * so we need to unpoison this area.
+	 */
+	kasan_unpoison_shadow(objp, size);
+	return size;
+}
+EXPORT_SYMBOL(ksize);
+
 /* Tracepoints definitions. */
 EXPORT_TRACEPOINT_SYMBOL(kmalloc);
 EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc);
diff --git a/mm/slob.c b/mm/slob.c
index 84aefd9b91ee..7f421d0ca9ab 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -527,7 +527,7 @@ void kfree(const void *block)
 EXPORT_SYMBOL(kfree);
 
 /* can't use ksize for kmem_cache_alloc memory, only kmalloc */
-size_t ksize(const void *block)
+size_t __ksize(const void *block)
 {
 	struct page *sp;
 	int align;
@@ -545,7 +545,7 @@ size_t ksize(const void *block)
 	m = (unsigned int *)(block - align);
 	return SLOB_UNITS(*m) * SLOB_UNIT;
 }
-EXPORT_SYMBOL(ksize);
+EXPORT_SYMBOL(__ksize);
 
 int __kmem_cache_create(struct kmem_cache *c, slab_flags_t flags)
 {
diff --git a/mm/slub.c b/mm/slub.c
index cd04dbd2b5d0..05a8d17dd9b2 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3901,7 +3901,7 @@ void __check_heap_object(const void *ptr, unsigned long n, struct page *page,
 }
 #endif /* CONFIG_HARDENED_USERCOPY */
 
-static size_t __ksize(const void *object)
+size_t __ksize(const void *object)
 {
 	struct page *page;
 
@@ -3917,17 +3917,7 @@ static size_t __ksize(const void *object)
 
 	return slab_ksize(page->slab_cache);
 }
-
-size_t ksize(const void *object)
-{
-	size_t size = __ksize(object);
-	/* We assume that ksize callers could use whole allocated area,
-	 * so we need to unpoison this area.
-	 */
-	kasan_unpoison_shadow(object, size);
-	return size;
-}
-EXPORT_SYMBOL(ksize);
+EXPORT_SYMBOL(__ksize);
 
 void kfree(const void *x)
 {
-- 
2.22.0.410.gd8fdbe21b5-goog