If the upperdirs in the member file's pathname does not 
exist. tarfile creates those paths with 0777 permission 
bits and does not honor umask.

This patch uses umask to set the ti.mode of the created 
directory for later usage in chmod.

--- tarfile.py  (revision 46993)
+++ tarfile.py  (working copy)
@@ -1560,7 +1560,9 @@
             ti = TarInfo()
             ti.name  = upperdirs
             ti.type  = DIRTYPE
-            ti.mode  = 0777
+            umask = os.umask(0)
+            ti.mode  = 0777 - umask
+            os.umask(umask)
             ti.mtime = tarinfo.mtime
             ti.uid   = tarinfo.uid
             ti.gid   = tarinfo.gid

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user_id=1541018

Above patch is wrong. The correct one is attached.

Hi, 

I can reproduce this problem on python 2.4 , and patch applies to python 2.5 too. Fix looks good to me.

In order to determine the current umask we have no other choice AFAIK than to set it with a bogus value, save the return value and restore it right away - as you proposed in your patch. The problem is that there is a small window of time between these two calls where the umask is invalid. This is especially bad in multi-threaded environments.

Any ideas?

umask(2) works in the same way, so there seems to be no unixy way to inspect umask without setting it.
I think the solution would be to make a C-level function to return the umask (by setting and resetting it). 
As the interpreter itself is single threaded, this is race-free.

I've come to the conclusion that it is a doubtful approach to take the mtime and ownership from the file and use it on the upper directories as well. So, I've come up with a totally different solution (cp. makedirs.diff) that abandons the use of os.umask() completely and uses a single call to os.makedirs() to create the missing directories.
It seems very attractive to me to do it this way, what do you think?
File Added: makedirs.diff

Committed my patch as rev. 53526.