From 081b1e69e99ea968781688fae766a9e1d0a46794 Mon Sep 17 00:00:00 2001
From: Michael Hanselmann <hansmi@google.com>
Date: Thu, 27 Sep 2007 13:03:08 +0000
Subject: [PATCH] Prevent race condition in CreateBackup().
Reviewed-by: ultrotter
---
lib/utils.py | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)
diff --git a/lib/utils.py b/lib/utils.py
index d964f8687..bc9a1046f 100644
--- a/lib/utils.py
+++ b/lib/utils.py
@@ -748,10 +748,20 @@ def CreateBackup(file_name):
raise errors.ProgrammerError("Can't make a backup of a non-file '%s'" %
file_name)
- # Warning: the following code contains a race condition when we create more
- # than one backup of the same file in a second.
- backup_name = file_name + '.backup-%d' % int(time.time())
- shutil.copyfile(file_name, backup_name)
+ prefix = '%s.backup-%d.' % (os.path.basename(file_name), int(time.time()))
+ dir = os.path.dirname(file_name)
+
+ fsrc = open(file_name, 'rb')
+ try:
+ (fd, backup_name) = tempfile.mkstemp(prefix=prefix, dir=dir)
+ fdst = os.fdopen(fd, 'wb')
+ try:
+ shutil.copyfileobj(fsrc, fdst)
+ finally:
+ fdst.close()
+ finally:
+ fsrc.close()
+
return backup_name
--
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