From: Paul Eggert <eggert@cs.ucla.edu>
Date: Mon, 5 Aug 2024 08:30:44 +0000 (-0700)
Subject: Fix unlikely pointer overflow in abspath
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=bba4427b5dfba7f9cdab8fa2cac1399fceda3058;p=thirdparty%2Fmake.git

Fix unlikely pointer overflow in abspath

* src/function.c (abspath): len is now ptrdiff_t,
to avoid GCC warning about comparing signed to unsigned.
It really is a pointer difference, after all.
Rejigger comparision to avoid undefined behavior
if dest + len is an invalid pointer.
---

diff --git a/src/function.c b/src/function.c
index 133e33a3..b4c38052 100644
--- a/src/function.c
+++ b/src/function.c
@@ -2119,7 +2119,7 @@ abspath (const char *name, char *apath)
 
   for (start = end = name; *start != '\0'; start = end)
     {
-      size_t len;
+      ptrdiff_t len;
 
       /* Skip sequence of multiple path-separators.  */
       while (ISDIRSEP (*start))
@@ -2147,7 +2147,7 @@ abspath (const char *name, char *apath)
           if (! ISDIRSEP (dest[-1]))
             *dest++ = '/';
 
-          if (dest + len >= apath_limit)
+          if (apath_limit - dest <= len)
             return NULL;
 
           dest = mempcpy (dest, start, len);