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 <keescook@chromium.org>

diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h
index 756c89b..da51a83 100644 (file)
--- 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
  *