[fuse-devel] [patch] Data corruption bug in python/example/xmp.py

[Robie B. <rb-...@ju...>]

Could someone commit the patch below please?

If you open a file to write but not append or truncate, then it appends
anyway, thus writing data to the wrong place. This is due to an
incorrect boolean test.

To reproduce:

$ echo abcdef > a
$ cat a
abcdef
$ python
Python 2.5.2 (r252:60911, Jul 31 2008, 17:31:22) 
[GCC 4.2.3 (Ubuntu 4.2.3-2ubuntu7)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> f = os.open('a', os.O_WRONLY)
>>> f
3
>>> os.write(f, 'ghi')
3
>>> os.close(f)
>>> 
$ cat a
abcdef
ghi

Except that it should say "ghidef". I've tested and the behaviour is
what I expect on a non-FUSE filesystem but is incorrect with FUSE and
xmp.py.

--- xmp.py.orig	2008-08-27 17:35:48.000000000 +0100
+++ xmp.py	2008-08-27 17:35:57.000000000 +0100
@@ -33,7 +33,7 @@
     md = {os.O_RDONLY: 'r', os.O_WRONLY: 'w', os.O_RDWR: 'w+'}
     m = md[flags & (os.O_RDONLY | os.O_WRONLY | os.O_RDWR)]
 
-    if flags | os.O_APPEND:
+    if flags & os.O_APPEND:
         m = m.replace('w', 'a', 1)
 
     return m