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.
> + return -E2BIG;
> +
> + /*
> + * Copy at most 'count' bytes, return early if we find a
If "count" is characters, this comment should not say "bytes". :)
> + * 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!
--
Kees Cook
