On 8/4/23 10:18, Kees Cook wrote:
On Sun, Jul 30, 2023 at 06:19:02PM +0200, Maximilian Luz wrote:
Add a ucs2_strscpy() function for UCS-2 strings. The behavior is
equivalent to the standard strscpy() function, just for 16-bit character
UCS-2 strings.
Signed-off-by: Maximilian Luz <luzmaximilian@xxxxxxxxx>
---
Changes in v5:
- Add ucs2_strscpy() instead of ucs2_strlcpy()
Patch introduced in v4.
---
include/linux/ucs2_string.h | 1 +
lib/ucs2_string.c | 35 +++++++++++++++++++++++++++++++++++
2 files changed, 36 insertions(+)
diff --git a/include/linux/ucs2_string.h b/include/linux/ucs2_string.h
index cf3ada3e820e..c499ae809c7d 100644
--- a/include/linux/ucs2_string.h
+++ b/include/linux/ucs2_string.h
@@ -10,6 +10,7 @@ typedef u16 ucs2_char_t;
unsigned long ucs2_strnlen(const ucs2_char_t *s, size_t maxlength);
unsigned long ucs2_strlen(const ucs2_char_t *s);
unsigned long ucs2_strsize(const ucs2_char_t *data, unsigned long maxlength);
+ssize_t ucs2_strscpy(ucs2_char_t *dst, const ucs2_char_t *src, size_t count);
int ucs2_strncmp(const ucs2_char_t *a, const ucs2_char_t *b, size_t len);
unsigned long ucs2_utf8size(const ucs2_char_t *src);
diff --git a/lib/ucs2_string.c b/lib/ucs2_string.c
index 0a559a42359b..b608129fcbdc 100644
--- a/lib/ucs2_string.c
+++ b/lib/ucs2_string.c
@@ -32,6 +32,41 @@ ucs2_strsize(const ucs2_char_t *data, unsigned long maxlength)
}
EXPORT_SYMBOL(ucs2_strsize);
+ssize_t ucs2_strscpy(ucs2_char_t *dst, const ucs2_char_t *src, size_t count)
+{
+ long res;
+
+ /*
+ * Ensure that we have a valid amount of space. We need to store at
+ * least one NUL-character.
+ */
+ if (count == 0 || WARN_ON_ONCE(count > INT_MAX))
Is "count" a measure of bytes or characters? It seems to be characters.
can you please add some kern-doc for this function to clarify this.
Also, I wonder if the above check should be "count > INT_MAX / 2" since
the INT_MAX is, generally, done in byte counts.
Count is a measure of characters. I'll add a doc-comment.
Regarding INT_MAX / 2: I'm fine with either. I'd change it to
INT_MAX / sizeof(*dst) if you say it's generally enforced in bytes.
+ return -E2BIG;
+
+ /*
+ * Copy at most 'count' bytes, return early if we find a
If "count" is characters, this comment should not say "bytes". :)
Correct. Will fix this.
+ * NUL-terminator.
+ */
+ for (res = 0; res < count; res++) {
+ ucs2_char_t c;
+
+ c = src[res];
+ dst[res] = c;
+
+ if (!c)
+ return res;
+ }
+
+ /*
+ * The loop above terminated without finding a NUL-terminator,
+ * exceeding the 'count': Enforce proper NUL-termination and return
+ * error.
+ */
+ dst[count - 1] = 0;
+ return -E2BIG;
+}
+EXPORT_SYMBOL(ucs2_strscpy);
+
int
ucs2_strncmp(const ucs2_char_t *a, const ucs2_char_t *b, size_t len)
{
--
2.41.0
Otherwise looks good to me!
Thanks!
Regards
Max
