glibc: CVE-2015-8777

The process_envvars function in elf/rtld.c in the GNU C Library (aka glibc or
libc6) before 2.23 allows local users to bypass a pointer-guarding protection
mechanism via a zero value of the LD_POINTER_GUARD environment variable.

(From OE-Core rev: 22570ba08d7c6157aec58764c73b1134405b0252)

References:
https://sourceware.org/bugzilla/show_bug.cgi?id=18928
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-8777

Reproducing steps available at:
http://hmarco.org/bugs/glibc_ptr_mangle_weakness.html
CVE request: http://seclists.org/oss-sec/2015/q3/504

Signed-off-by: Sona Sarmadi <sona.sarmadi@enea.com>
Signed-off-by: Tudor Florea <tudor.florea@enea.com>

2 files changed, 89 insertions, 0 deletions

diff --git a/meta/recipes-core/glibc/glibc/CVE-2015-8777.patch b/meta/recipes-core/glibc/glibc/CVE-2015-8777.patch
new file mode 100644
index 0000000000..ebcb59b1b5
--- /dev/null
+++ b/meta/recipes-core/glibc/glibc/CVE-2015-8777.patch
@@ -0,0 +1,88 @@
+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/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)
diff --git a/meta/recipes-core/glibc/glibc_2.20.bb b/meta/recipes-core/glibc/glibc_2.20.bb
index 4b0e927bfa..7bf4dbabf7 100644
--- a/meta/recipes-core/glibc/glibc_2.20.bb
+++ b/meta/recipes-core/glibc/glibc_2.20.bb
@@ -52,6 +52,7 @@ CVEPATCHES = "\
         file://CVE-2014-9761_1.patch \
         file://CVE-2014-9761_2.patch \
         file://CVE-2015-8776.patch \
+        file://CVE-2015-8777.patch \
     "
 LIC_FILES_CHKSUM = "file://LICENSES;md5=e9a558e243b36d3209f380deb394b213 \
       file://COPYING;md5=b234ee4d69f5fce4486a80fdaf4a4263 \