using PyMem_DEL() instead of PyObject_FREE() causes python 2.5 to double free or corrupt

[David Ross]

Binary package hint: python-fam

Please read:
http://effbot.org/pyfaq/why-does-my-c-extension-suddenly-crash-under-2.5.htm

Ubuntu Release: 7.04
Python Version: 2.5.1~rc1-0ubuntu3
Python-Fam: 1.1.1-2.1build1

Anybody running Python 2.5 and python-fam release or package 1.1.1-2.1build1 or lower will experience problems, specifically

To reproduce, use a program which utlizes Python 2.5 and python-fam. A webware example below.

apt-get install fam
apt-get install python-fam
wget http://www.webwareforpython.org/downloads/Webware/Webware-0.9.3.tar.gz
tar zxvf Webware-0.9.3.tar.gz
./Webware-0.9.3/bin/MakeAppWorkDir.py Crash
cd Crash
open Configs/AppServer.config for editing
change "AutoReload = False" to "AutoReload = True"
run ./AppServer

*** glibc detected *** python: double free or corruption (out): 0x084ff410 ***

the python instance is completely unresponsive.

Bug afflicts:
Python 2.5: unresponsive application
Python 2.4: unaffected

Tested the fix and it also allows the python-fam to use the libgamin supplied libfam which I accidently reported earlier as another issue.

[Matthias Klose (doko)]

David Ross schrieb:
> ** Attachment added: "python-fam-patch1.diff"
> http://librarian.launchpad.net/7715145/python-fam-patch1.diff
>

shouldn't PyObject_Del be used instead of PyObject_FREE ?

[David Ross (david-ross)]

Please copy and paste the line to a comment with the line number if you see any error. I don't see any instance of Del and PyObject on the same line.

[David Ross (david-ross)]

I see what you were asking now.

http://svn.python.org/projects/python/branches/release24-maint/Include/objimpl.h
http://svn.python.org/projects/python/branches/release25-maint/Include/objimpl.h

Comments say...
 Unless you have specific memory management requirements, use
! PyObject_{New, NewVar, Del}.

I'll use Del, and change NEW to New for naming consistency.

[Matthias Klose (doko)]

David Ross schrieb:
> I see what you were asking now.
>
> http://svn.python.org/projects/python/branches/release24-maint/Include/objimpl.h
> http://svn.python.org/projects/python/branches/release25-maint/Include/objimpl.h
>
> Comments say...
> Unless you have specific memory management requirements, use
> ! PyObject_{New, NewVar, Del}.
>
> I'll use Del, and change NEW to New for naming consistency.

thanks! A fixed package for feisty-proposed would be appreciated as well.

[David Ross (david-ross)]

A patch for feisty-proposed

[David Ross (david-ross)]

okay, the segfaulting when I was testing my application on another machine was because I didn't have FAM installed. Therefore, I changed the description to double free or corrupt.

[Martin Pitt (pitti)]

SRU: Please get this fixed in Gutsy first. About the patch: will that also work for Python 2.4?

[David Ross (david-ross)]

apologies for the file naming.

python-fam-patch2.diff is a patch for gutsy
python-fam-feisty-proposed-p1.diff is for the feisty updates

Python 2.4 still maps PyMem_DEL() to PyObject_ methods. The patch just changes bad code to correct code. The objects were originally created using PyObject, they SHOULD have been deleted using PyObject, instead the author used PyMem. I have no idea why, but PyObject is the correct method. Since feisty only supports 2.4 and 2.5, I tested both using webware as my test. Webware using python-fam quite a bit.

[Matthias Klose (doko)]

Martin Pitt schrieb:
> SRU: Please get this fixed in Gutsy first. About the patch: will that
> also work for Python 2.4?

yes

[Martin Pitt (pitti)]

Setting to needsinfo to get it out of the focus of ubutu-sru. Please set it back to confirmed once it is fixed in gutsy.

[Scott Kitterman (kitterman)]

Patched and uploaded for Gutsy. You need to mention the maintainer change in debian/changelog (I fixed it this time). Please monitor and make sure it builds correctly. Once it's built, you can pick up work on your SRU.

[Scott Kitterman (kitterman)]

Uploaded for feisty-proposed.

[Martin Pitt (pitti)]

Accpeted into -proposed. Please go ahead with QA testing

[Scott Kitterman (kitterman)]

To test, please add:

deb http://archive.ubuntu.com/ubuntu/ feisty-proposed universe

to your sources.list(5). Then, update and upgrade (or install) python-fam.

Then leave a comment here about if the fix works or not.

[David Ross (david-ross)]

the package appears to be fine. Thanks.

[Martin Pitt (pitti)]

Copied to feisty-updates, got one confirmation.