From 4dbb8e38a1aad1b2ac4abb2a6486d7f2c91a2248 Mon Sep 17 00:00:00 2001 From: David Howells Date: Tue, 4 Jul 2017 17:25:02 +0100 Subject: [PATCH] Provide a function to create a NUL-terminated string from unterminated data commit f35157417215ec138c920320c746fdb3e04ef1d5 upstream. 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 Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman --- 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 aa30789b0f65..98bb781a2eff 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -122,6 +122,7 @@ extern char *kstrdup(const char *s, gfp_t gfp); 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 d5259b62f8d7..818bbae84721 100644 --- a/mm/util.c +++ b/mm/util.c @@ -80,6 +80,8 @@ 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) { @@ -117,6 +119,28 @@ 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 *