From: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
When allocating an array of elements, users should check for
multiplication overflow or preferably use one of the provided helpers
like: kmalloc_array().
There's no krealloc_array() counterpart but there are many users who use
regular krealloc() to reallocate arrays. Let's provide an actual
krealloc_array() implementation.
While at it: add some documentation regarding krealloc.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
---
Documentation/core-api/memory-allocation.rst | 4 ++++
include/linux/slab.h | 18 ++++++++++++++++++
2 files changed, 22 insertions(+)
diff --git a/Documentation/core-api/memory-allocation.rst b/Documentation/core-api/memory-allocation.rst
index 4446a1ac36cc..5954ddf6ee13 100644
--- a/Documentation/core-api/memory-allocation.rst
+++ b/Documentation/core-api/memory-allocation.rst
@@ -147,6 +147,10 @@ The address of a chunk allocated with `kmalloc` is aligned to at least
ARCH_KMALLOC_MINALIGN bytes. For sizes which are a power of two, the
alignment is also guaranteed to be at least the respective size.
+Chunks allocated with kmalloc() can be resized with krealloc(). Similarly
+to kmalloc_array(): a helper for resizing arrays is provided in the form of
+krealloc_array().
+
For large allocations you can use vmalloc() and vzalloc(), or directly
request pages from the page allocator. The memory allocated by `vmalloc`
and related functions is not physically contiguous.
diff --git a/include/linux/slab.h b/include/linux/slab.h
index dd6897f62010..be4ba5867ac5 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -592,6 +592,24 @@ static inline void *kmalloc_array(size_t n, size_t size, gfp_t flags)
return __kmalloc(bytes, flags);
}
+/**
+ * krealloc_array - reallocate memory for an array.
+ * @p: pointer to the memory chunk to reallocate
+ * @new_n: new number of elements to alloc
+ * @new_size: new size of a single member of the array
+ * @flags: the type of memory to allocate (see kmalloc)
+ */
+static __must_check inline void *
+krealloc_array(void *p, size_t new_n, size_t new_size, gfp_t flags)
+{
+ size_t bytes;
+
+ if (unlikely(check_mul_overflow(new_n, new_size, &bytes)))
+ return NULL;
+
+ return krealloc(p, bytes, flags);
+}
+
/**
* kcalloc - allocate memory for an array. The memory is set to zero.
* @n: number of elements.
--
2.29.1
