Bug 211529

Summary:	Lock validator warning involving TCP and IPv6
Product:	Red Hat Enterprise Linux 5	Reporter:	Paul Moore <paul.moore>
Component:	kernel	Assignee:	Thomas Graf <tgraf>
Status:	CLOSED NOTABUG	QA Contact:	Brian Brock <bbrock>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	5.0	CC:	dzickus, eparis, rkhan
Target Milestone:	---
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2007-08-22 21:17:40 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Paul Moore 2006-10-19 20:38:29 UTC

Description of problem:
I am running into a lock validator warning indicating a potential recursive
locking issues in tcp_v6_rcv() and sk_clone().  A brief investigation and
mailing list search makes me believe this is not a real "bug" but the lock
validator warning should somehow be corrected.  The following post seems to
indicate this is a known issue in the mainline kernel but there is no indication
as to what the fix is:

 * http://lkml.org/lkml/2006/7/31/85

Version-Release number of selected component (if applicable):
 - Kernel 2.6.18-1.2727.2.1.el5.lspp.52 found on Steve Grubb's people page
 - SELinux MLS policy version 2.3.19-2

How reproducible:
Everytime

Steps to Reproduce:
1. Boot into SELinux enforcing mode
2. Configure NetLabel as follows:
    # netlabelctl -p cipsov4 add pass doi:1 tags:1
    # netlabelctl -p map del default
    # netlabelctl -p map add default protocol:cipsov4,1
3. Restart sshd
4. Connect to localhost using ssh

Actual results:
The lock validator issues a warning very similar to the one shown in the URL above.

Expected results:
No lock validator warnings.

Additional info:

Comment 1 RHEL Program Management 2006-11-13 15:20:32 UTC

This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux major release.  Product Management has requested further
review of this request by Red Hat Engineering, for potential inclusion in a Red
Hat Enterprise Linux Major release.  This request is not yet committed for
inclusion.

Comment 3 Thomas Graf 2007-05-09 21:50:52 UTC

Hi Paul,

Sorry for taking so long to look at this. I've tried to reproduce the problem
with 2.6.18-18 following the steps you describe but didn't succeed. It's
very likely due to my very limited knowledge of NetLabel policies though.
I've booted with selinux=1, configured netlabel like above and restarted
sshd. I wasn't able to connect afterwards but didn't see any lockdep warnings
either.

Anyways, I've looked at any possible socket related lockdep patches upstream
which could be backported but haven't found any, they've all been integrated
already. Can you reproduce the bug with upstream kernels? Would you be willing
to try with a recent RHEL-5 kernel so we can verify that the lockdep problem
still exists?

Comment 4 Paul Moore 2007-05-09 22:01:48 UTC

Hi Thomas,

No problem on the delay, I'll try to reproduce this with a recent RHEL5 kernel 
and get back to you.  It might take a little while though as I'm currently 
swamped on another RHEL5 project (LSPP evaluation).  The good news is that I 
have been doing a lot of network testing since this bug was originally posted 
and I haven't seen any lockdep warnings in recent kernels - the problem may 
have gone away.

Thanks for looking into this.

Comment 5 Don Zickus 2007-05-10 14:25:13 UTC

Please note, that around beta2, we disabled the lockdep warnings for performance
reasons.  They were re-enabled post GA (starting with -9.el5) but then disabled
again with -17.el5.  

In order to see lockdep warning messages please use the kernel-debug variant
kernels staring with -17.el5.

These kernels can be found under people.redhat.com/dzickus/el5

Comment 6 Paul Moore 2007-06-13 14:19:40 UTC

I just tried to recreate these lockdep warnings using the 
kernel-2.6.18-23.el5.ia64 kernel RPM found here:

 * http://people.redhat.com/dzickus/el5/23.el5/ia64

... and was not able to reproduce the warnings.  I guess at this point I'd 
consider this a "solved" issue, something must have changed between the 
earlier version of the kernel and this current version.  Sorry about the 
firedrill guys.