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Groups > linux.kernel > #1638941

[PATCH 01/14] Provide a function to create a NUL-terminated string from unterminated data

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Provide a function, kmemdup_nul(), 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@redhat.com>
---

 include/linux/string.h |    1 +
 mm/util.c              |   24 ++++++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/include/linux/string.h b/include/linux/string.h
index 26b6f6a66f83..0c88c0a1a72b 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -123,6 +123,7 @@ 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 void *kmemdup(const void *src, size_t len, gfp_t gfp);
+extern char *kmemdup_nul(const char *s, size_t len, 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 656dc5e37a87..be68664bfb73 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -83,6 +83,8 @@ EXPORT_SYMBOL(kstrdup_const);
  * @s: the string to duplicate
  * @max: read at most @max chars from @s
  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
+ *
+ * Note: Use kmemdup_nul() instead if the size is known exactly.
  */
 char *kstrndup(const char *s, size_t max, gfp_t gfp)
 {
@@ -121,6 +123,28 @@ void *kmemdup(const void *src, size_t len, gfp_t gfp)
 EXPORT_SYMBOL(kmemdup);
 
 /**
+ * kmemdup_nul - 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 *kmemdup_nul(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(kmemdup_nul);
+
+/**
  * memdup_user - duplicate memory region from user space
  *
  * @src: source address in user space

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[RFC][PATCH 00/14] VFS: Introduce superblock configuration context David Howells <dhowells@redhat.com> - 2017-05-10 18:20 +0200
  [PATCH 01/14] Provide a function to create a NUL-terminated string  from unterminated data David Howells <dhowells@redhat.com> - 2017-05-10 18:20 +0200
  [PATCH 07/14] Implement fsopen() to prepare for a mount David Howells <dhowells@redhat.com> - 2017-05-10 18:30 +0200
    Re: [PATCH 07/14] Implement fsopen() to prepare for a mount Sargun Dhillon <sargun@sargun.me> - 2017-05-11 00:10 +0200
      Re: [PATCH 07/14] Implement fsopen() to prepare for a mount David Howells <dhowells@redhat.com> - 2017-05-11 16:40 +0200
    Re: [PATCH 07/14] Implement fsopen() to prepare for a mount Jeff Layton <jlayton@redhat.com> - 2017-05-11 16:40 +0200
  [PATCH 08/14] Implement fsmount() to effect a pre-configured mount David Howells <dhowells@redhat.com> - 2017-05-10 18:30 +0200
  [PATCH 11/14] proc: Add superblock config support to procfs David Howells <dhowells@redhat.com> - 2017-05-10 18:30 +0200
  [PATCH 13/14] Support legacy filesystems David Howells <dhowells@redhat.com> - 2017-05-10 18:30 +0200
  [PATCH 03/14] VFS: Make get_mnt_ns() return the namespace David Howells <dhowells@redhat.com> - 2017-05-10 18:30 +0200
  [PATCH 05/14] VFS: Provide empty name qstr David Howells <dhowells@redhat.com> - 2017-05-10 18:30 +0200
  [PATCH 02/14] Clean up whitespace in fs/namespace.c David Howells <dhowells@redhat.com> - 2017-05-10 18:30 +0200
  [PATCH 10/14] procfs: Move proc_fill_super() to fs/proc/root.c David Howells <dhowells@redhat.com> - 2017-05-10 18:30 +0200
  [PATCH 09/14] Sample program for driving fsopen/fsmount David Howells <dhowells@redhat.com> - 2017-05-10 18:30 +0200
  [PATCH 04/14] VFS: Make get_filesystem() return the affected  filesystem David Howells <dhowells@redhat.com> - 2017-05-10 18:30 +0200
  Re: [PATCH 06/14] VFS: Introduce a superblock configuration context Al Viro <viro@ZenIV.linux.org.uk> - 2017-05-11 09:30 +0200
  Re: [PATCH 14/14] Add commands to create or update a superblock Al Viro <viro@ZenIV.linux.org.uk> - 2017-05-11 09:40 +0200
    Re: [PATCH 14/14] Add commands to create or update a superblock Miklos Szeredi <mszeredi@redhat.com> - 2017-05-11 10:20 +0200

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