linux-hardening - [PATCH v4 1/8] mm/util: Introduce kmemdup

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Date: Wed, 11 Oct 2023 15:04:05 +0530
From: Kartik <kkartik@...dia.com>
To: <thierry.reding@...il.com>, <jonathanh@...dia.com>,
	<keescook@...omium.org>, <andy@...nel.org>, <akpm@...ux-foundation.org>,
	<arnd@...db.de>, <petlozup@...dia.com>, <pshete@...dia.com>,
	<kkartik@...dia.com>, <ulf.hansson@...aro.org>, <frank.li@...o.com>,
	<robh@...nel.org>, <stefank@...dia.com>, <pdeschrijver@...dia.com>,
	<linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-hardening@...r.kernel.org>, <linux-mm@...ck.org>
Subject: [PATCH v4 1/8] mm/util: Introduce kmemdup_array() to duplicate an array

Introduce function kmemdup_array(), that will copy `n` number of
elements from a given array `src` to `dst`.

On success, kmemdup_array() returns 0 and copy the elements from `src`
to newly allocated array `dst`, it also stores number of elements
copied from `src` array to `dst_count` parameter. On failure, this
returns a negative integer value containing the error value.

Signed-off-by: Kartik <kkartik@...dia.com>
---
 include/linux/string.h |  2 ++
 mm/util.c              | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/include/linux/string.h b/include/linux/string.h
index dbfc66400050..6245a7918b05 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -179,6 +179,8 @@ 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 int kmemdup_array(void **dst, size_t *dst_count, 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);
diff --git a/mm/util.c b/mm/util.c
index 6eddd891198e..a7c87a119be1 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -135,6 +135,40 @@ void *kmemdup(const void *src, size_t len, gfp_t gfp)
 }
 EXPORT_SYMBOL(kmemdup);
 
+/**
+ * kmemdup_array - duplicate a given array.
+ *
+ * @dst: reference to the pointer to store address of duplicated array.
+ * @dst_count: number of elements in the duplicated 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: Returns 0 on success, on failure this returns a negative error value.
+ */
+int kmemdup_array(void **dst, size_t *dst_count, const void *src, size_t element_size, size_t count,
+		  gfp_t gfp)
+{
+	size_t size;
+
+	*dst_count = 0;
+
+	if (!src || !element_size || !count)
+		return -EINVAL;
+
+	size = size_mul(element_size, count);
+
+	*dst = kmemdup(src, size, gfp);
+	if (*dst)
+		return -ENOMEM;
+
+	*dst_count = size / element_size;
+
+	return 0;
+}
+EXPORT_SYMBOL(kmemdup_array);
+
 /**
  * kvmemdup - duplicate region of memory
  *
-- 
2.34.1