From a014cecd82b71b70a6a843e250e06b541ad524f7 Mon Sep 17 00:00:00 2001
From: Florian Weimer <fweimer@redhat.com>
Date: Thu, 15 Oct 2015 09:23:07 +0200
Subject: [PATCH] Always enable pointer guard [BZ #18928]

Honoring the LD_POINTER_GUARD environment variable in AT_SECURE mode
has security implications.  This commit enables pointer guard
unconditionally, and the environment variable is now ignored.

        [BZ #18928]
        * sysdeps/generic/ldsodefs.h (struct rtld_global_ro): Remove
        _dl_pointer_guard member.
        * elf/rtld.c (_rtld_global_ro): Remove _dl_pointer_guard
        initializer.
        (security_init): Always set up pointer guard.
        (process_envvars): Do not process LD_POINTER_GUARD.

Upstream-Status: Backport
CVE: CVE-2015-8777
[Yocto # 8980]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commit;h=a014cecd82b71b70a6a843e250e06b541ad524f7

Signed-off-by: Armin Kuster <akuster@mvista.com>

---
 ChangeLog                  | 10 ++++++++++
 NEWS                       | 13 ++++++++-----
 elf/rtld.c                 | 15 ++++-----------
 sysdeps/generic/ldsodefs.h |  3 ---
 4 files changed, 22 insertions(+), 19 deletions(-)

Index: git/ChangeLog
===================================================================
--- git.orig/ChangeLog
+++ git/ChangeLog
@@ -1,3 +1,14 @@
+2015-10-15  Florian Weimer  <fweimer@redhat.com>
+
+   [BZ #18928]
+   * sysdeps/generic/ldsodefs.h (struct rtld_global_ro): Remove
+   _dl_pointer_guard member.
+   * elf/rtld.c (_rtld_global_ro): Remove _dl_pointer_guard
+   initializer.
+   (security_init): Always set up pointer guard.
+   (process_envvars): Do not process LD_POINTER_GUARD.
+
+
 2015-08-10  Maxim Ostapenko  <m.ostapenko@partner.samsung.com>
 
 	[BZ #18778]
Index: git/NEWS
===================================================================
--- git.orig/NEWS
+++ git/NEWS
@@ -34,7 +34,10 @@ Version 2.22
   18533, 18534, 18536, 18539, 18540, 18542, 18544, 18545, 18546, 18547,
   18549, 18553, 18557, 18558, 18569, 18583, 18585, 18586, 18592, 18593,
   18594, 18602, 18612, 18613, 18619, 18633, 18635, 18641, 18643, 18648,
-  18657, 18676, 18694, 18696.
+  18657, 18676, 18694, 18696, 18928.
+
+* The LD_POINTER_GUARD environment variable can no longer be used to
+  disable the pointer guard feature.  It is always enabled.
 
 * Cache information can be queried via sysconf() function on s390 e.g. with
   _SC_LEVEL1_ICACHE_SIZE as argument.
Index: git/elf/rtld.c
===================================================================
--- git.orig/elf/rtld.c
+++ git/elf/rtld.c
@@ -163,7 +163,6 @@ struct rtld_global_ro _rtld_global_ro at
     ._dl_hwcap_mask = HWCAP_IMPORTANT,
     ._dl_lazy = 1,
     ._dl_fpu_control = _FPU_DEFAULT,
-    ._dl_pointer_guard = 1,
     ._dl_pagesize = EXEC_PAGESIZE,
     ._dl_inhibit_cache = 0,
 
@@ -710,15 +709,12 @@ security_init (void)
 #endif
 
   /* Set up the pointer guard as well, if necessary.  */
-  if (GLRO(dl_pointer_guard))
-    {
-      uintptr_t pointer_chk_guard = _dl_setup_pointer_guard (_dl_random,
-							     stack_chk_guard);
+  uintptr_t pointer_chk_guard
+    = _dl_setup_pointer_guard (_dl_random, stack_chk_guard);
 #ifdef THREAD_SET_POINTER_GUARD
-      THREAD_SET_POINTER_GUARD (pointer_chk_guard);
+  THREAD_SET_POINTER_GUARD (pointer_chk_guard);
 #endif
-      __pointer_chk_guard_local = pointer_chk_guard;
-    }
+  __pointer_chk_guard_local = pointer_chk_guard;
 
   /* We do not need the _dl_random value anymore.  The less
      information we leave behind, the better, so clear the
@@ -2478,9 +2474,6 @@ process_envvars (enum mode *modep)
 	      GLRO(dl_use_load_bias) = envline[14] == '1' ? -1 : 0;
 	      break;
 	    }
-
-	  if (memcmp (envline, "POINTER_GUARD", 13) == 0)
-	    GLRO(dl_pointer_guard) = envline[14] != '0';
 	  break;
 
 	case 14:
Index: git/sysdeps/generic/ldsodefs.h
===================================================================
--- git.orig/sysdeps/generic/ldsodefs.h
+++ git/sysdeps/generic/ldsodefs.h
@@ -600,9 +600,6 @@ struct rtld_global_ro
   /* List of auditing interfaces.  */
   struct audit_ifaces *_dl_audit;
   unsigned int _dl_naudit;
-
-  /* 0 if internal pointer values should not be guarded, 1 if they should.  */
-  EXTERN int _dl_pointer_guard;
 };
 # define __rtld_global_attribute__
 # if IS_IN (rtld)