Ubuntu
libx11 package

Thread unsafe access to internal linked list, breaks Origin games in Wine

Bug #1062534 reported by Alessandro Pignotti on 2012-10-05

This bug affects 3 people

Affects		Status	Importance	Assigned to	Milestone
	xlibs	Unknown	Medium	freedesktop-bugs #55678
	libx11 (Ubuntu)	Triaged	Medium	Unassigned

Bug Description

In file src/xlibi18n/lcConv.c the following linked list head is defined

static XlcConverterList conv_list = NULL;

Which is then modified by _XlcSetConverter and get_converter in a non thread-safe manner. Inside get_converter the list is reorderder to increase the efficiency of looking up the same element the next time, but this is especially dangerous since a seemingly read-only method is actually modifying the data.

Modifying the list in such thread unsafe manner does case the list to become garbled in some workloads and causes infinite loops when the get_converter is invoked. The solution I suggest is to add a mutex or spinlock around accesses to the linked list, I would it myself but I'm not sure about what is the usual mutex implementation for this project.

Tags:

Revision history for this message

In freedesktop.org Bugzilla #55678, Alessandro Pignotti (a-pignotti) wrote on 2012-10-05:

In file src/xlibi18n/lcConv.c the following linked list head is defined

static XlcConverterList conv_list = NULL;

Bug Watch Updater (bug-watch-updater) on 2012-10-05

Changed in xlibs:
importance:	Unknown → Medium
status:	Unknown → Confirmed

Revision history for this message

In freedesktop.org Bugzilla #55678, Alessandro Pignotti (a-pignotti) wrote on 2012-10-05:

Also the following definitions:

static XlcDatabaseList _db_list = (XlcDatabaseList)NULL;

in file src/xlibi18n/lcDB.c is affected by the similar issues.

It looks like the localization support inside libx11 is generally not thread safe.

Revision history for this message

In freedesktop.org Bugzilla #55678, Scott Ritchie (scottritchie) wrote on 2012-10-11:

It should be noted that this is causing a lockup on the Origin game client under Wine, making a good chunk of games unplayable.

Revision history for this message

Scott Ritchie (scottritchie) wrote on 2012-11-08: Re: Type unsafe access to internal linked list, breaks Origin games in Wine

This bug affects the Origin games downloader in Wine, rendering a great swath of games unplayable.

Changed in libx11 (Ubuntu):
status:	New → Confirmed
summary:	- Type unsafe access to internal linked list + Type unsafe access to internal linked list, breaks Origin games in Wine

Revision history for this message

Alessandro Pignotti (a-pignotti) wrote on 2012-11-08:

I've realized that I've made a typo in the type. The problem is with _thread_ safety, not type safety of course.

summary:

- Type unsafe access to internal linked list, breaks Origin games in Wine
+ Thread unsafe access to internal linked list, breaks Origin games in
+ Wine

Revision history for this message

Alessandro Pignotti (a-pignotti) wrote on 2012-11-27:

0001-Improve-thread-safety-of-localization.patch Edit (3.8 KiB, text/plain)

I'm attaching two internal pacthes that we use to fix the issue. They should be consider hacks to make the problem more clear.

Revision history for this message

Alessandro Pignotti (a-pignotti) wrote on 2012-11-27:

0001-Remove-an-optimization-that-is-thread-unsafe.patch Edit (829 bytes, text/plain)

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Ubuntu Foundations Team Bug Bot (crichton) wrote on 2012-11-27:

The attachment "0001-Improve-thread-safety-of-localization.patch" of this bug report has been identified as being a patch. The ubuntu-reviewers team has been subscribed to the bug report so that they can review the patch. In the event that this is in fact not a patch you can resolve this situation by removing the tag 'patch' from the bug report and editing the attachment so that it is not flagged as a patch. Additionally, if you are member of the ubuntu-reviewers team please also unsubscribe the team from this bug report.

[This is an automated message performed by a Launchpad user owned by Brian Murray. Please contact him regarding any issues with the action taken in this bug report.]

tags:

added: patch

Bryce Harrington (bryce) on 2013-04-08

Changed in libx11 (Ubuntu):
assignee:	nobody → Canonical X.org (canonical-x)
status:	Confirmed → Triaged
importance:	Undecided → High

Revision history for this message

Timo Aaltonen (tjaalton) wrote on 2017-03-30:

you should post patches on xorg-devel@ and discuss the bug on the upstream bugtracker, if you want this to get forward

Changed in libx11 (Ubuntu):
assignee:	Canonical X.org (canonical-x) → nobody
importance:	High → Medium

Revision history for this message

In freedesktop.org Bugzilla #55678, Pavel Řezníček (cigydd-5) wrote on 2017-03-30:

#10

Created attachment 130584
A hack to improve the thread safety of the libX11 localization

Originally posted here: https://bugs.launchpad.net/ubuntu/+source/libx11/+bug/1062534 by Alessandro Pignotti

Revision history for this message

In freedesktop.org Bugzilla #55678, Pavel Řezníček (cigydd-5) wrote on 2017-03-30:

#11

Created attachment 130585
A hack to remove an optimization that is thread unsafe

Originally posted here: https://bugs.launchpad.net/ubuntu/+source/libx11/+bug/1062534 by Alessandro Pignotti

Revision history for this message

In freedesktop.org Bugzilla #55678, Pavel Řezníček (cigydd-5) wrote on 2017-03-30:

#12

Appended two patches from Alessandro Pignotti originally posted on the Ubuntu Bugzilla. They may or may not still be valid.

According to Alessandro's words, "They should be considered hacks to make the problem more clear."

Trying to attract some attention to this bug because I face it on a regular basis playing Lord of the Rings Online on Wine still after 5 years a patch has been proposed.

I'm a bit experienced in programming but only in Pascal and Python so I'm trying to find someone more experienced who could possibly fix it. If nobody responds, maybe I'll try to fix it myself…

Revision history for this message

In freedesktop.org Bugzilla #55678, Gitlab-migration (gitlab-migration) wrote on 2018-08-10:

#13

-- GitLab Migration Automatic Message --

This bug has been migrated to freedesktop.org's GitLab instance and has been closed from further activity.

You can subscribe and participate further through the new bug through this link to our GitLab instance: https://gitlab.freedesktop.org/xorg/lib/libx11/issues/24.