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string: Allow 2-argument strscpy_pad() 

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>
Reviewed-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook 2024-02-02 03:40:23 -08:00
parent e6584c3964
commit 8366d124ec
1 changed files with 20 additions and 13 deletions
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33
include/linux/string.h
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@ -77,6 +77,10 @@ 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
@ -102,11 +106,23 @@ 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
* @dst: Where to copy the string to
* @src: Where to copy the string from
* @count: Size of destination buffer
* @...: Size of destination buffer
*
* Copy the string, or as much of it as fits, into the dest buffer. The
* behavior is undefined if the string buffers overlap. The destination
@ -122,17 +138,8 @@ 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 *);