From 55c84a5cf2c72a821719823ef2ebef01b119025b Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Tue, 4 Apr 2023 14:24:27 -0700 Subject: [PATCH] fortify: strcat: Move definition to use fortified strlcat() Move the definition of fortified strcat() to after strlcat() to use it for bounds checking. Signed-off-by: Kees Cook --- include/linux/fortify-string.h | 53 +++++++++++++++++++++--------------------- 1 file changed, 26 insertions(+), 27 deletions(-) diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h index 756c89b..da51a83 100644 --- a/include/linux/fortify-string.h +++ b/include/linux/fortify-string.h @@ -151,33 +151,6 @@ char *strncpy(char * const POS p, const char *q, __kernel_size_t size) return __underlying_strncpy(p, q, size); } -/** - * strcat - Append a string to an existing string - * - * @p: pointer to NUL-terminated string to append to - * @q: pointer to NUL-terminated source string to append from - * - * Do not use this function. While FORTIFY_SOURCE tries to avoid - * read and write overflows, this is only possible when the - * destination buffer size is known to the compiler. Prefer - * building the string with formatting, via scnprintf() or similar. - * At the very least, use strncat(). - * - * Returns @p. - * - */ -__FORTIFY_INLINE __diagnose_as(__builtin_strcat, 1, 2) -char *strcat(char * const POS p, const char *q) -{ - const size_t p_size = __member_size(p); - - if (p_size == SIZE_MAX) - return __underlying_strcat(p, q); - if (strlcat(p, q, p_size) >= p_size) - fortify_panic(__func__); - return p; -} - extern __kernel_size_t __real_strnlen(const char *, __kernel_size_t) __RENAME(strnlen); /** * strnlen - Return bounded count of characters in a NUL-terminated string @@ -435,6 +408,32 @@ size_t strlcat(char * const POS p, const char * const POS q, size_t avail) return wanted; } +/* Defined after fortified strlcat() to reuse it. */ +/** + * strcat - Append a string to an existing string + * + * @p: pointer to NUL-terminated string to append to + * @q: pointer to NUL-terminated source string to append from + * + * Do not use this function. While FORTIFY_SOURCE tries to avoid + * read and write overflows, this is only possible when the + * destination buffer size is known to the compiler. Prefer + * building the string with formatting, via scnprintf() or similar. + * At the very least, use strncat(). + * + * Returns @p. + * + */ +__FORTIFY_INLINE __diagnose_as(__builtin_strcat, 1, 2) +char *strcat(char * const POS p, const char *q) +{ + const size_t p_size = __member_size(p); + + if (strlcat(p, q, p_size) >= p_size) + fortify_panic(__func__); + return p; +} + /** * strncat - Append a string to an existing string * -- 2.7.4