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Subject[PATCH 04/13] mm: Use array_size() helpers for kmalloc()
Date
Instead of open-coded multiplication, use the new array_size() helper
to detect overflow in kmalloc()-family functions.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
include/linux/slab.h | 31 +++++++++++++++++++++++--------
1 file changed, 23 insertions(+), 8 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 81ebd71f8c03..d03e0726e136 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -13,6 +13,7 @@
#define _LINUX_SLAB_H

#include <linux/gfp.h>
+#include <linux/overflow.h>
#include <linux/types.h>
#include <linux/workqueue.h>

@@ -499,6 +500,8 @@ static __always_inline void *kmalloc_large(size_t size, gfp_t flags)
*/
static __always_inline void *kmalloc(size_t size, gfp_t flags)
{
+ if (size == SIZE_MAX)
+ return NULL;
if (__builtin_constant_p(size)) {
if (size > KMALLOC_MAX_CACHE_SIZE)
return kmalloc_large(size, flags);
@@ -539,6 +542,8 @@ static __always_inline unsigned int kmalloc_size(unsigned int n)

static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
{
+ if (size == SIZE_MAX)
+ return NULL;
#ifndef CONFIG_SLOB
if (__builtin_constant_p(size) &&
size <= KMALLOC_MAX_CACHE_SIZE && !(flags & GFP_DMA)) {
@@ -624,11 +629,13 @@ int memcg_update_all_caches(int num_memcgs);
*/
static inline void *kmalloc_array(size_t n, size_t size, gfp_t flags)
{
- if (size != 0 && n > SIZE_MAX / size)
+ size_t bytes = array_size(n, size);
+
+ if (bytes == SIZE_MAX)
return NULL;
if (__builtin_constant_p(n) && __builtin_constant_p(size))
- return kmalloc(n * size, flags);
- return __kmalloc(n * size, flags);
+ return kmalloc(bytes, flags);
+ return __kmalloc(bytes, flags);
}

/**
@@ -639,7 +646,9 @@ static inline void *kmalloc_array(size_t n, size_t size, gfp_t flags)
*/
static inline void *kcalloc(size_t n, size_t size, gfp_t flags)
{
- return kmalloc_array(n, size, flags | __GFP_ZERO);
+ size_t bytes = array_size(n, size);
+
+ return kmalloc(bytes, flags | __GFP_ZERO);
}

/*
@@ -657,16 +666,22 @@ extern void *__kmalloc_track_caller(size_t, gfp_t, unsigned long);
static inline void *kmalloc_array_node(size_t n, size_t size, gfp_t flags,
int node)
{
- if (size != 0 && n > SIZE_MAX / size)
+ size_t bytes = array_size(n, size);
+
+ if (bytes == SIZE_MAX)
return NULL;
if (__builtin_constant_p(n) && __builtin_constant_p(size))
- return kmalloc_node(n * size, flags, node);
- return __kmalloc_node(n * size, flags, node);
+ return kmalloc_node(bytes, flags, node);
+ return __kmalloc_node(bytes, flags, node);
}

static inline void *kcalloc_node(size_t n, size_t size, gfp_t flags, int node)
{
- return kmalloc_array_node(n, size, flags | __GFP_ZERO, node);
+ size_t bytes = array_size(n, size);
+
+ if (bytes == SIZE_MAX)
+ return NULL;
+ return kmalloc_node(bytes, flags | __GFP_ZERO, node);
}


--
2.17.0
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