[PATCH v4 4/5] mm/slab: Refactor common ksize KASAN logic into slab_common.c

Marco Elver
2019-06-27T09:45:21Z

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@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: kasan-dev@googlegroups.com
Cc: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org
---
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