linux-kernel - [PATCH 1/9] Provide a function to create a NUL-terminated string from unterminated data

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Date:   Wed, 03 May 2017 17:04:42 +0100
From:   David Howells <dhowells@...hat.com>
To:     viro@...iv.linux.org.uk
Cc:     linux-fsdevel@...r.kernel.org, dhowells@...hat.com,
        linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        mszeredi@...hat.com
Subject: [PATCH 1/9] Provide a function to create a NUL-terminated string
 from unterminated data

Provide a function, kstrcreate(), that will create a NUL-terminated string
from an unterminated character array where the length is known in advance.

This is better than kstrndup() in situations where we already know the
string length as the strnlen() in kstrndup() is superfluous.

Signed-off-by: David Howells <dhowells@...hat.com>
---

 include/linux/string.h |    1 +
 mm/util.c              |   22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/include/linux/string.h b/include/linux/string.h
index 26b6f6a66f83..5596ae56ce0a 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -122,6 +122,7 @@ extern void kfree_const(const void *x);
 extern char *kstrdup(const char *s, gfp_t gfp) __malloc;
 extern const char *kstrdup_const(const char *s, gfp_t gfp);
 extern char *kstrndup(const char *s, size_t len, gfp_t gfp);
+extern char *kstrcreate(const char *s, size_t len, gfp_t gfp);
 extern void *kmemdup(const void *src, size_t len, gfp_t gfp);
 
 extern char **argv_split(gfp_t gfp, const char *str, int *argcp);
diff --git a/mm/util.c b/mm/util.c
index 656dc5e37a87..01887bbdb11e 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -103,6 +103,28 @@ char *kstrndup(const char *s, size_t max, gfp_t gfp)
 EXPORT_SYMBOL(kstrndup);
 
 /**
+ * kstrcreate - Create a NUL-terminated string from unterminated data
+ * @s: The data to stringify
+ * @len: The size of the data
+ * @gfp: the GFP mask used in the kmalloc() call when allocating memory
+ */
+char *kstrcreate(const char *s, size_t len, gfp_t gfp)
+{
+	char *buf;
+
+	if (!s)
+		return NULL;
+
+	buf = kmalloc_track_caller(len + 1, gfp);
+	if (buf) {
+		memcpy(buf, s, len);
+		buf[len] = '\0';
+	}
+	return buf;
+}
+EXPORT_SYMBOL(kstrcreate);
+
+/**
  * kmemdup - duplicate region of memory
  *
  * @src: memory region to duplicate