Cast pointers to uintptr_t to avoid potential signedness errors.

Based on patch from yuanjie.huang at windriver.com via OpenSSH bz#2608,
with & ok millert, ok deraadt.

1 files changed, 8 insertions, 2 deletions

diff --git a/src/lib/libc/string/strlcpy.c b/src/lib/libc/string/strlcpy.c
index 5fcf084aaa..f282834680 100644
--- a/src/lib/libc/string/strlcpy.c
+++ b/src/lib/libc/string/strlcpy.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: strlcpy.c,v 1.13 2015/08/31 02:53:57 guenther Exp $   */
+/*      $OpenBSD: strlcpy.c,v 1.14 2016/10/14 18:19:04 dtucker Exp $    */
 
 /*
  * Copyright (c) 1998, 2015 Todd C. Miller <Todd.Miller@courtesan.com>
@@ -18,6 +18,7 @@
 
 #include <sys/types.h>
 #include <string.h>
+#include <stdint.h>
 
 /*
  * Copy string src to buffer dst of size dsize.  At most dsize-1
@@ -46,6 +47,11 @@ strlcpy(char *dst, const char *src, size_t dsize)
                         ;
         }
 
-        return(src - osrc - 1); /* count does not include NUL */
+        /*
+         * Cast pointers to unsigned type before calculation, to avoid signed
+         * overflow when the string ends where the MSB has changed.
+         * Return value does not include NUL.
+         */
+        return((uintptr_t)src - (uintptr_t)osrc - 1); 
 }
 DEF_WEAK(strlcpy);