[tor-commits] [stem/master] Making lsof cwd checks account for permissions

[atagar at torproject.org]

commit 479a620ee8d3351e07d1bc86bec3f1107c04cc69
Author: Damian Johnson <atagar at torproject.org>
Date:   Thu Jan 12 09:17:20 2012 -0800

    Making lsof cwd checks account for permissions
    
    With the anti-debugger tor change the /proc/<pid>/cwd symlink becomes only
    readable by root. This causes lsof queries for a process' cwd to return the
    proc path with a message saying that permission is denied, and the sys tools
    misparsed that as meaning that the cwd _was_ the proc path.
---
 stem/util/system.py |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/stem/util/system.py b/stem/util/system.py
index 8eced97..f58f698 100644
--- a/stem/util/system.py
+++ b/stem/util/system.py
@@ -451,7 +451,13 @@ def get_cwd(pid):
     results = call(GET_CWD_LSOF % pid)
     
     if results and len(results) == 2 and results[1].startswith("n/"):
-      return results[1][1:].strip()
+      lsof_result = results[1][1:].strip()
+      
+      # If we lack read permissions for the cwd then it returns...
+      # p2683
+      # n/proc/2683/cwd (readlink: Permission denied)
+      
+      if not " " in lsof_result: return lsof_result
     else:
       log.debug("%s we got unexpected output from lsof: %s" % (logging_prefix, results))