diff mbox series

[v2,3/4] string: Allow 2-argument strscpy_pad()

Message ID 20240205123525.1379299-3-keescook@chromium.org
State New
Headers
Series string: Allow 2-argument strscpy() |

Commit Message

Kees Cook Feb. 5, 2024, 12:35 p.m. UTC 
  Similar to strscpy(), update strscpy_pad()'s 3rd argument to be
optional when the destination is a compile-time known size array.

Cc: Andy Shevchenko <andy@kernel.org>
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 include/linux/string.h | 29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

Comments

Geert Uytterhoeven Feb. 5, 2024, 12:48 p.m. UTC | #1 
Hi Kees,

On Mon, Feb 5, 2024 at 1:36 PM Kees Cook <keescook@chromium.org> wrote:
> Similar to strscpy(), update strscpy_pad()'s 3rd argument to be
> optional when the destination is a compile-time known size array.
>
> Cc: Andy Shevchenko <andy@kernel.org>
> Cc: linux-hardening@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

Thanks for your patch!

> --- a/include/linux/string.h
> +++ b/include/linux/string.h
> @@ -78,6 +78,10 @@ ssize_t sized_strscpy(char *, const char *, size_t);
>         sized_strscpy(dst, src, sizeof(dst) + __must_be_array(dst))
>  #define __strscpy1(dst, src, size)     sized_strscpy(dst, src, size)
>
> +#define __strscpy_pad0(dst, src, ...)  \
> +       sized_strscpy_pad(dst, src, sizeof(dst) + __must_be_array(dst))
> +#define __strscpy_pad1(dst, src, size) sized_strscpy_pad(dst, src, size)

(dst) etc.

> @@ -123,17 +139,8 @@ ssize_t sized_strscpy(char *, const char *, size_t);
>   * * The number of characters copied (not including the trailing %NULs)
>   * * -E2BIG if count is 0 or @src was truncated.
>   */
> -#define strscpy_pad(dest, src, count)  ({                      \
> -       char *__dst = (dest);                                           \
> -       const char *__src = (src);                                      \
> -       const size_t __count = (count);                                 \
> -       ssize_t __wrote;                                                \
> -                                                                       \
> -       __wrote = strscpy(__dst, __src, __count);                       \
> -       if (__wrote >= 0 && __wrote < __count)                          \
> -               memset(__dst + __wrote + 1, 0, __count - __wrote - 1);  \
> -       __wrote;                                                        \
> -})
> +#define strscpy_pad(dst, src, ...)     \
> +       CONCATENATE(__strscpy_pad, COUNT_ARGS(__VA_ARGS__))(dst, src, __VA_ARGS__)

Likewise,

Gr{oetje,eeting}s,

                        Geert
andy@kernel.org Feb. 5, 2024, 12:57 p.m. UTC | #2 
On Mon, Feb 05, 2024 at 01:48:51PM +0100, Geert Uytterhoeven wrote:
> On Mon, Feb 5, 2024 at 1:36 PM Kees Cook <keescook@chromium.org> wrote:

..

> > +#define __strscpy_pad1(dst, src, size) sized_strscpy_pad(dst, src, size)
> 
> (dst) etc.

Makes a little sense here. Are you expecting, e.g., dst to be 'a, b' (w/o
quotes where a and b are expressions)?

..

> > +#define strscpy_pad(dst, src, ...)     \
> > +       CONCATENATE(__strscpy_pad, COUNT_ARGS(__VA_ARGS__))(dst, src, __VA_ARGS__)
> 
> Likewise,

Ditto.
diff mbox series

Patch

diff --git a/include/linux/string.h b/include/linux/string.h
index a21371aa2fd6..4f0f27013418 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -78,6 +78,10 @@  ssize_t sized_strscpy(char *, const char *, size_t);
 	sized_strscpy(dst, src, sizeof(dst) + __must_be_array(dst))
 #define __strscpy1(dst, src, size)	sized_strscpy(dst, src, size)
 
+#define __strscpy_pad0(dst, src, ...)	\
+	sized_strscpy_pad(dst, src, sizeof(dst) + __must_be_array(dst))
+#define __strscpy_pad1(dst, src, size)	sized_strscpy_pad(dst, src, size)
+
 /**
  * strscpy - Copy a C-string into a sized buffer
  * @dst: Where to copy the string to
@@ -103,6 +107,18 @@  ssize_t sized_strscpy(char *, const char *, size_t);
 #define strscpy(dst, src, ...)	\
 	CONCATENATE(__strscpy, COUNT_ARGS(__VA_ARGS__))(dst, src, __VA_ARGS__)
 
+#define sized_strscpy_pad(dest, src, count)	({			\
+	char *__dst = (dest);						\
+	const char *__src = (src);					\
+	const size_t __count = (count);					\
+	ssize_t __wrote;						\
+									\
+	__wrote = sized_strscpy(__dst, __src, __count);			\
+	if (__wrote >= 0 && __wrote < __count)				\
+		memset(__dst + __wrote + 1, 0, __count - __wrote - 1);	\
+	__wrote;							\
+})
+
 /**
  * strscpy_pad() - Copy a C-string into a sized buffer
  * @dest: Where to copy the string to
@@ -123,17 +139,8 @@  ssize_t sized_strscpy(char *, const char *, size_t);
  * * The number of characters copied (not including the trailing %NULs)
  * * -E2BIG if count is 0 or @src was truncated.
  */
-#define strscpy_pad(dest, src, count)	({			\
-	char *__dst = (dest);						\
-	const char *__src = (src);					\
-	const size_t __count = (count);					\
-	ssize_t __wrote;						\
-									\
-	__wrote = strscpy(__dst, __src, __count);			\
-	if (__wrote >= 0 && __wrote < __count)				\
-		memset(__dst + __wrote + 1, 0, __count - __wrote - 1);	\
-	__wrote;							\
-})
+#define strscpy_pad(dst, src, ...)	\
+	CONCATENATE(__strscpy_pad, COUNT_ARGS(__VA_ARGS__))(dst, src, __VA_ARGS__)
 
 #ifndef __HAVE_ARCH_STRCAT
 extern char * strcat(char *, const char *);