From 3328e98bcbf2930cd7eea3e6c92ad5dcbdf4794f Mon Sep 17 00:00:00 2001
From: Yuanjie Huang <yuanjie.huang@windriver.com>
Date: Wed, 24 Aug 2016 03:15:43 +0000
Subject: [PATCH] Fix potential signed overflow in pointer arithmatic

Pointer arithmatic results in implementation defined signed integer
type, so that 's - src' in strlcpy and others may trigger signed overflow.
In case of compilation by gcc or clang with -ftrapv option, the overflow
would lead to program abort.

Upstream-Status: Submitted [http://bugzilla.mindrot.org/show_bug.cgi?id=2608]

Signed-off-by: Yuanjie Huang <yuanjie.huang@windriver.com>
---
 openbsd-compat/strlcat.c | 8 ++++++--
 openbsd-compat/strlcpy.c | 8 ++++++--
 openbsd-compat/strnlen.c | 8 ++++++--
 3 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/openbsd-compat/strlcat.c b/openbsd-compat/strlcat.c
index bcc1b61..e758ebf 100644
--- a/openbsd-compat/strlcat.c
+++ b/openbsd-compat/strlcat.c
@@ -23,6 +23,7 @@
 
 #include <sys/types.h>
 #include <string.h>
+#include <stdint.h>
 
 /*
  * Appends src to string dst of size siz (unlike strncat, siz is the
@@ -55,8 +56,11 @@ strlcat(char *dst, const char *src, size_t siz)
 		s++;
 	}
 	*d = '\0';
-
-	return(dlen + (s - src));	/* 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 (dlen + ((uintptr_t)s - (uintptr_t)src));	/* count does not include NUL */
 }
 
 #endif /* !HAVE_STRLCAT */
diff --git a/openbsd-compat/strlcpy.c b/openbsd-compat/strlcpy.c
index b4b1b60..b06f374 100644
--- a/openbsd-compat/strlcpy.c
+++ b/openbsd-compat/strlcpy.c
@@ -23,6 +23,7 @@
 
 #include <sys/types.h>
 #include <string.h>
+#include <stdint.h>
 
 /*
  * Copy src to string dst of size siz.  At most siz-1 characters
@@ -51,8 +52,11 @@ strlcpy(char *dst, const char *src, size_t siz)
 		while (*s++)
 			;
 	}
-
-	return(s - src - 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 ((uintptr_t)s - (uintptr_t)src - 1);	/* count does not include NUL */
 }
 
 #endif /* !HAVE_STRLCPY */
diff --git a/openbsd-compat/strnlen.c b/openbsd-compat/strnlen.c
index 93d5155..9b8de5d 100644
--- a/openbsd-compat/strnlen.c
+++ b/openbsd-compat/strnlen.c
@@ -23,6 +23,7 @@
 #include <sys/types.h>
 
 #include <string.h>
+#include <stdint.h>
 
 size_t
 strnlen(const char *str, size_t maxlen)
@@ -31,7 +32,10 @@ strnlen(const char *str, size_t maxlen)
 
 	for (cp = str; maxlen != 0 && *cp != '\0'; cp++, maxlen--)
 		;
-
-	return (size_t)(cp - str);
+        /*
+	 * Cast pointers to unsigned type before calculation, to avoid signed
+	 * overflow when the string ends where the MSB has changed.
+	 */
+	return (size_t)((uintptr_t)cp - (uintptr_t)str);
 }
 #endif
-- 
1.9.1

