Submitted By:            Matt Burgess <matthew_at_linuxfromscratch_dot_org>
Date:                    2010-10-24
Initial Package Version: 2.12.1
Upstream Status:         From upstream
Origin:                  http://sourceware.org/ml/libc-hacker/2010-10/msg00007.html
Description:             Fixes a security vulnerability, described in detail at
                         http://marc.info/?l=full-disclosure&m=128739684614072&w=2,
                         which allows a local attacker to gain root if they can
                         create a hard link to a setuid root binary.

diff -Naur glibc-2.12.1.orig/elf/dl-load.c glibc-2.12.1/elf/dl-load.c
--- glibc-2.12.1.orig/elf/dl-load.c	2010-07-27 11:34:39.000000000 +0000
+++ glibc-2.12.1/elf/dl-load.c	2010-10-24 16:05:54.825480309 +0000
@@ -169,8 +169,7 @@
 
 
 static size_t
-is_dst (const char *start, const char *name, const char *str,
-	int is_path, int secure)
+is_dst (const char *start, const char *name, const char *str, int is_path)
 {
   size_t len;
   bool is_curly = false;
@@ -199,11 +198,6 @@
 	   && (!is_path || name[len] != ':'))
     return 0;
 
-  if (__builtin_expect (secure, 0)
-      && ((name[len] != '\0' && (!is_path || name[len] != ':'))
-	  || (name != start + 1 && (!is_path || name[-2] != ':'))))
-    return 0;
-
   return len;
 }
 
@@ -218,13 +212,12 @@
     {
       size_t len;
 
-      /* $ORIGIN is not expanded for SUID/GUID programs (except if it
-	 is $ORIGIN alone) and it must always appear first in path.  */
+      /* $ORIGIN is not expanded for SUID/GUID programs.  */
       ++name;
-      if ((len = is_dst (start, name, "ORIGIN", is_path,
-			 INTUSE(__libc_enable_secure))) != 0
-	  || (len = is_dst (start, name, "PLATFORM", is_path, 0)) != 0
-	  || (len = is_dst (start, name, "LIB", is_path, 0)) != 0)
+      if (((len = is_dst (start, name, "ORIGIN", is_path)) != 0
+	   && !INTUSE(__libc_enable_secure))
+	  || (len = is_dst (start, name, "PLATFORM", is_path)) != 0
+	  || (len = is_dst (start, name, "LIB", is_path)) != 0)
 	++cnt;
 
       name = strchr (name + len, '$');
@@ -256,9 +249,12 @@
 	  size_t len;
 
 	  ++name;
-	  if ((len = is_dst (start, name, "ORIGIN", is_path,
-			     INTUSE(__libc_enable_secure))) != 0)
+	  if ((len = is_dst (start, name, "ORIGIN", is_path)) != 0)
 	    {
+	      /* Ignore this path element in SUID/SGID programs.  */
+	      if (INTUSE(__libc_enable_secure))
+		repl = (const char *) -1;
+	      else
 #ifndef SHARED
 	      if (l == NULL)
 		repl = _dl_get_origin ();
@@ -266,9 +262,9 @@
 #endif
 		repl = l->l_origin;
 	    }
-	  else if ((len = is_dst (start, name, "PLATFORM", is_path, 0)) != 0)
+	  else if ((len = is_dst (start, name, "PLATFORM", is_path)) != 0)
 	    repl = GLRO(dl_platform);
-	  else if ((len = is_dst (start, name, "LIB", is_path, 0)) != 0)
+	  else if ((len = is_dst (start, name, "LIB", is_path)) != 0)
 	    repl = DL_DST_LIB;
 
 	  if (repl != NULL && repl != (const char *) -1)