mm/util: Introduce kmemdup_array()

Introduce kmemdup_array() API to duplicate `n` number of elements
from a given array. This internally uses kmemdup to allocate and duplicate
the `src` array.
Signed-off-by: Kartik <kkartik@nvidia.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>

include/linux/string.h

@@ -217,6 +217,7 @@ extern char *kstrndup(const char *s, size_t len, gfp_t gfp);
 extern void *kmemdup(const void *src, size_t len, gfp_t gfp) __realloc_size(2);
 extern void *kvmemdup(const void *src, size_t len, gfp_t gfp) __realloc_size(2);
 extern char *kmemdup_nul(const char *s, size_t len, gfp_t gfp);
+extern void *kmemdup_array(const void *src, size_t element_size, size_t count, gfp_t gfp);
 
 extern char **argv_split(gfp_t gfp, const char *str, int *argcp);
 extern void argv_free(char **argv);

mm/util.c

@@ -135,6 +135,23 @@ void *kmemdup(const void *src, size_t len, gfp_t gfp)
 }
 EXPORT_SYMBOL(kmemdup);
 
+/**
+ * kmemdup_array - duplicate a given array.
+ *
+ * @src: array to duplicate.
+ * @element_size: size of each element of array.
+ * @count: number of elements to duplicate from array.
+ * @gfp: GFP mask to use.
+ *
+ * Return: duplicated array of @src or %NULL in case of error,
+ * result is physically contiguous. Use kfree() to free.
+ */
+void *kmemdup_array(const void *src, size_t element_size, size_t count, gfp_t gfp)
+{
+	return kmemdup(src, size_mul(element_size, count), gfp);
+}
+EXPORT_SYMBOL(kmemdup_array);
+
 /**
  * kvmemdup - duplicate region of memory
  *