Subject: Re: bug#16335: Segmentation fault when using cp -a with SELinux and fakeroot
From: Pádraig Brady <[email-masked]>
To: Nicolas Iooss <[email-masked]>
Cc: [email-masked]
Date: Mon, 13 Jan 2014 14:50:13 +0000
List-Id: <debbugs-submit.debbugs.gnu.org>

I'm going to push the attached very soon, to address this.

thanks,
Pádraig.
From 2b3b5bfcd5f4161d17c0bc3d43f6edcfc4a2b294 Mon Sep 17 00:00:00 2001
From: Nicolas Looss <[email-masked]>
Date: Sat, 4 Jan 2014 03:03:51 +0000
Subject: [PATCH] copy: fix a segfault in SELinux context copying code

* src/selinux.c (restorecon_private): On ArchLinux the
`fakeroot cp -a file1 file2` command segfaulted due
to getfscreatecon() returning a NULL context.
So map this to the sometimes ignored ENODATA error,
rather than crashing.
* tests/cp/no-ctx.sh: Add a new test case.
* tests/local.mk: Reference the new test.
* NEWS: Mention the fix.
Fixes http://bugs.gnu.org/16335
---
 NEWS               |    5 ++++
 src/selinux.c      |    5 ++++
 tests/cp/no-ctx.sh |   53 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 tests/local.mk     |    1 +
 4 files changed, 64 insertions(+), 0 deletions(-)
 create mode 100755 tests/cp/no-ctx.sh

diff --git a/NEWS b/NEWS
index 3e1f9c6..699a7d3 100644
--- a/NEWS
+++ b/NEWS
@@ -9,6 +9,11 @@ GNU coreutils NEWS                                    -*- outline -*-
   the context of an existing directory to that of its last copied descendent.
   [bug introduced in coreutils-8.22]
 
+  cp -a, mv, and install --preserve-context, no longer seg fault when running
+  with SELinux enabled, when copying from file systems that return an error
+  when reading the SELinux context for a file.
+  [bug introduced in coreutils-8.22]
+
 
 * Noteworthy changes in release 8.22 (2013-12-13) [stable]
 
diff --git a/src/selinux.c b/src/selinux.c
index cd38a81..016db16 100644
--- a/src/selinux.c
+++ b/src/selinux.c
@@ -192,6 +192,11 @@ restorecon_private (char const *path, bool local)
     {
       if (getfscreatecon (&tcon) < 0)
         return rc;
+      if (!tcon)
+        {
+          errno = ENODATA;
+          return rc;
+        }
       rc = lsetfilecon (path, tcon);
       freecon (tcon);
       return rc;
diff --git a/tests/cp/no-ctx.sh b/tests/cp/no-ctx.sh
new file mode 100755
index 0000000..59d30de
--- /dev/null
+++ b/tests/cp/no-ctx.sh
@@ -0,0 +1,53 @@
+#!/bin/sh
+# Ensure we handle file systems returning no SELinux context,
+# which triggered a segmentation fault in coreutils-8.22.
+# This test is skipped on systems that lack LD_PRELOAD support; that's fine.
+# Similarly, on a system that lacks lgetfilecon altogether, skipping it is fine.
+
+# Copyright (C) 2014 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
+print_ver_ cp
+require_gcc_shared_
+
+# Replace each getfilecon and lgetfilecon call with a call to these stubs.
+cat > k.c <<'EOF' || framework_failure_
+#include <selinux/selinux.h>
+#include <errno.h>
+
+int getfilecon (const char *path, security_context_t *con)
+{ errno=ENODATA; return -1; }
+int lgetfilecon (const char *path, security_context_t *con)
+{ errno=ENODATA; return -1; }
+EOF
+
+# Then compile/link it:
+$CC -shared -fPIC -O2 k.c -o k.so \
+  || framework_failure_ 'failed to build SELinux shared library'
+
+touch file_src
+
+# New file with SELinux context optionally included
+LD_PRELOAD=./k.so cp -a file_src file_dst || fail=1
+
+# Existing file with SELinux context optionally included
+LD_PRELOAD=./k.so cp -a file_src file_dst || fail=1
+
+# ENODATA should give an immediate error when required to preserve ctx
+# This is debatable, and maybe we should not fail when no context available?
+LD_PRELOAD=./k.so cp --preserve=context file_src file_dst && fail=1
+
+Exit $fail
diff --git a/tests/local.mk b/tests/local.mk
index dc7341c..9d556f6 100644
--- a/tests/local.mk
+++ b/tests/local.mk
@@ -161,6 +161,7 @@ all_tests =					\
   tests/rm/ext3-perf.sh				\
   tests/rm/cycle.sh				\
   tests/cp/link-heap.sh				\
+  tests/cp/no-ctx.sh				\
   tests/misc/tty-eof.pl				\
   tests/tail-2/inotify-hash-abuse.sh		\
   tests/tail-2/inotify-hash-abuse2.sh		\
-- 
1.7.7.6