Restore SIGPIPE default action for subprocesses

Python ignores SIGPIPE on startup, because it prefers to check every
write and raise an IOError exception rather than taking the signal. Most
Unix subprocesses don't expect to work this way. This patch (adapted
from Colin Watson's post at http://tinyurl.com/2a7mzh5) sets SIGPIPE
back to the default action for nova.utils.execute and nova-rootwrap
created subprocesses.

Fixes bug 1053364

Change-Id: I17e1629bb4ef4268515c6734ddb6e12746739c52

2 files changed, 17 insertions, 0 deletions

diff --git a/bin/nova-rootwrap b/bin/nova-rootwrap
index b903f3030..a28205a80 100755
--- a/bin/nova-rootwrap
+++ b/bin/nova-rootwrap
@@ -34,6 +34,7 @@
 
 import ConfigParser
 import os
+import signal
 import subprocess
 import sys
 
@@ -42,6 +43,13 @@ RC_UNAUTHORIZED = 99
 RC_NOCOMMAND = 98
 RC_BADCONFIG = 97
 
+
+def _subprocess_setup():
+    # Python installs a SIGPIPE handler by default. This is usually not what
+    # non-Python subprocesses expect.
+    signal.signal(signal.SIGPIPE, signal.SIG_DFL)
+
+
 if __name__ == '__main__':
     # Split arguments, require at least a command
     execname = sys.argv.pop(0)
@@ -77,6 +85,7 @@ if __name__ == '__main__':
                                stdin=sys.stdin,
                                stdout=sys.stdout,
                                stderr=sys.stderr,
+                               preexec_fn=_subprocess_setup,
                                env=filtermatch.get_environment(userargs))
         obj.wait()
         sys.exit(obj.returncode)
diff --git a/nova/utils.py b/nova/utils.py
index f2642f07c..015ff915a 100644
--- a/nova/utils.py
+++ b/nova/utils.py
@@ -31,6 +31,7 @@ import random
 import re
 import shlex
 import shutil
+import signal
 import socket
 import struct
 import sys
@@ -112,6 +113,12 @@ def vpn_ping(address, port, timeout=0.05, session_id=None):
         return server_sess
 
 
+def _subprocess_setup():
+    # Python installs a SIGPIPE handler by default. This is usually not what
+    # non-Python subprocesses expect.
+    signal.signal(signal.SIGPIPE, signal.SIG_DFL)
+
+
 def execute(*cmd, **kwargs):
     """Helper method to execute command with optional retry.
 
@@ -180,6 +187,7 @@ def execute(*cmd, **kwargs):
                                    stdout=_PIPE,
                                    stderr=_PIPE,
                                    close_fds=True,
+                                   preexec_fn=_subprocess_setup,
                                    shell=shell)
             result = None
             if process_input is not None: