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author | Kees Cook <keescook@chromium.org> | 2024-02-02 03:18:14 -0800 |
---|---|---|
committer | Kees Cook <keescook@chromium.org> | 2024-02-20 20:47:31 -0800 |
commit | f478898e0aa74a759fcf629a3ee8b040467b8533 (patch) | |
tree | a4ce041e524eb2eb11a998b3ba09eec0bf3ec69d /include/linux/string.h | |
parent | ubsan: Reintroduce signed overflow sanitizer (diff) | |
download | wireguard-linux-f478898e0aa74a759fcf629a3ee8b040467b8533.tar.xz wireguard-linux-f478898e0aa74a759fcf629a3ee8b040467b8533.zip |
string: Redefine strscpy_pad() as a macro
In preparation for making strscpy_pad()'s 3rd argument optional, redefine
it as a macro. This also has the benefit of allowing greater FORITFY
introspection, as it couldn't see into the strscpy() nor the memset()
within strscpy_pad().
Cc: Andy Shevchenko <andy@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: <linux-hardening@vger.kernel.org>
Reviewed-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Diffstat (limited to 'include/linux/string.h')
-rw-r--r-- | include/linux/string.h | 33 |
1 files changed, 31 insertions, 2 deletions
diff --git a/include/linux/string.h b/include/linux/string.h index ab148d8dbfc1..78b28004c5ba 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -70,8 +70,37 @@ extern char * strncpy(char *,const char *, __kernel_size_t); ssize_t strscpy(char *, const char *, size_t); #endif -/* Wraps calls to strscpy()/memset(), no arch specific code required */ -ssize_t strscpy_pad(char *dest, const char *src, size_t count); +/** + * strscpy_pad() - Copy a C-string into a sized buffer + * @dest: Where to copy the string to + * @src: Where to copy the string from + * @count: 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 + * buffer is always %NUL terminated, unless it's zero-sized. + * + * If the source string is shorter than the destination buffer, the + * remaining bytes in the buffer will be filled with %NUL bytes. + * + * For full explanation of why you may want to consider using the + * 'strscpy' functions please see the function docstring for strscpy(). + * + * Returns: + * * 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; \ +}) #ifndef __HAVE_ARCH_STRCAT extern char * strcat(char *, const char *); |