@@ -45,34 +45,41 @@ void kfree_const(const void *x)
EXPORT_SYMBOL(kfree_const);
/**
- * kstrdup - allocate space for and copy an existing string
- * @s: the string to duplicate
+ * __kmemdup_nul - Create a NUL-terminated string from @s, which might be unterminated.
+ * @s: The data to copy
+ * @len: The size of the data, not including the NUL terminator
* @gfp: the GFP mask used in the kmalloc() call when allocating memory
*
- * Return: newly allocated copy of @s or %NULL in case of error
+ * Return: newly allocated copy of @s with NUL-termination or %NULL in
+ * case of error
*/
-noinline
-char *kstrdup(const char *s, gfp_t gfp)
+static __always_inline char *__kmemdup_nul(const char *s, size_t len, gfp_t gfp)
{
- size_t len;
char *buf;
- if (!s)
+ /* '+1' for the NUL terminator */
+ buf = kmalloc_track_caller(len + 1, gfp);
+ if (!buf)
return NULL;
- len = strlen(s) + 1;
- buf = kmalloc_track_caller(len, gfp);
- if (buf) {
- memcpy(buf, s, len);
- /*
- * During memcpy(), the string might be updated to a new value,
- * which could be longer than the string when strlen() is
- * called. Therefore, we need to add a NUL terminator.
- */
- buf[len - 1] = '\0';
- }
+ memcpy(buf, s, len);
+ /* Ensure the buf is always NUL-terminated, regardless of @s. */
+ buf[len] = '\0';
return buf;
}
+
+/**
+ * kstrdup - allocate space for and copy an existing string
+ * @s: the string to duplicate
+ * @gfp: the GFP mask used in the kmalloc() call when allocating memory
+ *
+ * Return: newly allocated copy of @s or %NULL in case of error
+ */
+noinline
+char *kstrdup(const char *s, gfp_t gfp)
+{
+ return s ? __kmemdup_nul(s, strlen(s), gfp) : NULL;
+}
EXPORT_SYMBOL(kstrdup);
/**
@@ -107,19 +114,7 @@ EXPORT_SYMBOL(kstrdup_const);
*/
char *kstrndup(const char *s, size_t max, gfp_t gfp)
{
- size_t len;
- char *buf;
-
- if (!s)
- return NULL;
-
- len = strnlen(s, max);
- buf = kmalloc_track_caller(len+1, gfp);
- if (buf) {
- memcpy(buf, s, len);
- buf[len] = '\0';
- }
- return buf;
+ return s ? __kmemdup_nul(s, strnlen(s, max), gfp) : NULL;
}
EXPORT_SYMBOL(kstrndup);
@@ -193,17 +188,7 @@ EXPORT_SYMBOL(kvmemdup);
*/
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;
+ return s ? __kmemdup_nul(s, len, gfp) : NULL;
}
EXPORT_SYMBOL(kmemdup_nul);
These three functions follow the same pattern. To deduplicate the code, let's introduce a common helper __kmemdup_nul(). Suggested-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Yafang Shao <laoar.shao@gmail.com> Cc: Simon Horman <horms@kernel.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Alejandro Colomar <alx@kernel.org> --- mm/util.c | 69 ++++++++++++++++++++++--------------------------------- 1 file changed, 27 insertions(+), 42 deletions(-)