From 474f2887ce756bb5a14defb25e67b89678be0b8c Mon Sep 17 00:00:00 2001
From: sin
Date: Thu, 29 Jan 2015 12:42:41 +0000
Subject: Add compile-time checks as well

---
 include/stdio.h | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

(limited to 'include/stdio.h')

diff --git a/include/stdio.h b/include/stdio.h
index 070d4e5..285fe21 100644
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -6,17 +6,24 @@
 
 #if defined(_FORTIFY_SOURCE) && _FORTIFY_SOURCE > 0 && defined(__OPTIMIZE__) && __OPTIMIZE__ > 0
 
+#define __errordecl(name, msg) extern void name(void) __attribute__((__error__(msg)))
+
+__errordecl(__fgets_error, "fgets: buffer overflow detected");
 static inline __attribute__ ((always_inline))
 char *
 __fortify_fgets(char *s, int n, FILE *fp)
 {
 	size_t bos = __builtin_object_size(s, 0);
 
+	if (__builtin_constant_p(n) && (size_t)n > bos)
+		__fgets_error();
+
 	if ((size_t)n > bos)
 		__builtin_trap();
 	return fgets(s, n, fp);
 }
 
+__errordecl(__vsnprintf_error, "vsnprintf: buffer overflow detected");
 static inline
 __attribute__ ((always_inline))
 __attribute__ ((__format__ (printf, 3, 0)))
@@ -27,6 +34,9 @@ __fortify_vsnprintf(char *__restrict s, size_t n, const char *__restrict fmt,
 {
 	size_t bos = __builtin_object_size(s, 0);
 
+	if (__builtin_constant_p(n) && n > bos)
+		__vsnprintf_error();
+
 	if (n > bos)
 		__builtin_trap();
 	return vsnprintf(s, n, fmt, ap);
@@ -36,13 +46,17 @@ __fortify_vsnprintf(char *__restrict s, size_t n, const char *__restrict fmt,
 #define fgets(s, n, fp) __fortify_fgets(s, n, fp)
 #undef vsnprintf
 #define vsnprintf(s, n, fmt, ap) __fortify_vsnprintf(s, n, fmt, ap)
+
+__errordecl(__snprintf_error, "snprintf: buffer overflow detected");
 #undef snprintf
 #define snprintf(s, n, fmt, ...) ({ \
 	size_t _n = (n); \
 	size_t bos = __builtin_object_size(s, 0); \
+	if (__builtin_constant_p(_n) && _n > bos) \
+		__snprintf_error(); \
 	if (_n > bos) \
 		__builtin_trap(); \
-	snprintf(s, _n, fmt, __VA_ARGS__); \
+	snprintf(s, _n, fmt, ## __VA_ARGS__); \
 })
 
 #endif
-- 
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