[PATCH v7 1/3] mm: add kstrdup_trimnl function

[Sebastian Capella <sebastian.capella@xxxxxxxxxx>]

kstrdup_trimnl creates a duplicate of the passed in
null-terminated string.  If a trailing newline is found, it
is removed before duplicating.  This is useful for strings
coming from sysfs that often include trailing whitespace due to
user input.

Signed-off-by: Sebastian Capella <sebastian.capella@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx> (commit_signer:5/10=50%)
Cc: Michel Lespinasse <walken@xxxxxxxxxx>
Cc: Shaohua Li <shli@xxxxxxxxxx>
Cc: Jerome Marchand <jmarchan@xxxxxxxxxx>
Cc: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Joe Perches <joe@xxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
---
 include/linux/string.h |    1 +
 mm/util.c              |   29 +++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/include/linux/string.h b/include/linux/string.h
index ac889c5..e7ec8c0 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -114,6 +114,7 @@ void *memchr_inv(const void *s, int c, size_t n);
 
 extern char *kstrdup(const char *s, gfp_t gfp);
 extern char *kstrndup(const char *s, size_t len, gfp_t gfp);
+extern char *kstrdup_trimnl(const char *s, 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 808f375..0bab867 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -1,6 +1,7 @@
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/string.h>
+#include <linux/ctype.h>
 #include <linux/export.h>
 #include <linux/err.h>
 #include <linux/sched.h>
@@ -63,6 +64,34 @@ char *kstrndup(const char *s, size_t max, gfp_t gfp)
 EXPORT_SYMBOL(kstrndup);
 
 /**
+ * kstrdup_trimnl - Copy a %NUL terminated string, removing one trailing
+ * newline if present.
+ * @s: the string to duplicate
+ * @gfp: the GFP mask used in the kmalloc() call when allocating memory
+ *
+ * Returns an address, which the caller must kfree, containing
+ * a duplicate of the passed string with a single trailing newline
+ * removed if present.
+ */
+char *kstrdup_trimnl(const char *s, gfp_t gfp)
+{
+	char *buf;
+	size_t len = strlen(s);
+	if (len >= 1 && s[len - 1] == '\n')
+		len--;
+
+	buf = kmalloc_track_caller(len + 1, gfp);
+	if (!buf)
+		return NULL;
+
+	memcpy(buf, s, len);
+	buf[len] = '\0';
+
+	return buf;
+}
+EXPORT_SYMBOL(kstrdup_trimnl);
+
+/**
  * kmemdup - duplicate region of memory
  *
  * @src: memory region to duplicate
-- 
1.7.9.5

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