multipathd crashing with segfault with selinux enabled

I have a Dell 2950 running 64-bit RHEL5.1 and am having a
problem with
multipathd crashing with a segfault.  It seems to happen
only when
selinux is enabled.  I quick search turned up a nearly
identical bug
reported on CentOS:

http://bugs.c
entos.org/view.php?id=2746

This causes a problem in that, if a path fails, it's never
restored
(since that's the job of multipathd).  We had a drive
failure last night
that would have normally cause an 60-90 second outage (while
the drive
was retried and eventually marked offline by the array) but,
since
mutlipathd had failed it causes a much longer outage.

When I was alerted to the problem I was able to put selinux
into
permissive mode and get multipathd running again, which
restored the
paths and things seemed OK after that, but obviously this
isn't the way
it should work.

I pretty sure this problem is "new".  This system
has been running with
it's current configuration for a few months and we've never
seen this
before.  Has anyone else noticed problems with multipathd
not running on
RHEL5.1 systems with selinux enabled?

Thanks,
Tom


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On Tue, 2008-04-22 at 11:14 -0400, Tom Sightler wrote:

> I pretty sure this problem is "new".  This
system has been running with
> it's current configuration for a few months and we've
never seen this
> before.  Has anyone else noticed problems with
multipathd not running on
> RHEL5.1 systems with selinux enabled?

Sorry to answer my own email, but a second search through
bugzilla
turned up Bug 438150: Multipathd Segfaults on load when
SELinux is
enabled.  Also there are multiple bugs with recent
multipathd versions
and selinux regarding ramfs caching but it appears those
fixes haven't
made it into the wild yet.  I guess I'm off to open a
support case and
see if I can get a fixed version.

Later,
Tom




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On Tue, 2008-04-22 at 12:59 -0400, Tom Sightler wrote:
> Sorry to answer my own email, but a second search
through bugzilla
> turned up Bug 438150: Multipathd Segfaults on load when
SELinux is
> enabled.  Also there are multiple bugs with recent
multipathd versions
> and selinux regarding ramfs caching but it appears
those fixes haven't
> made it into the wild yet.  I guess I'm off to open a
support case and
> see if I can get a fixed version.

Just to follow up on this, if you have a RHEL5.1 system with
SELinux
enabled and current versions of device-mapper-multipath
tools, you might
want to be aware the multipath is probably broken for you. 
Path
failures should be detected, but it's likely that multipathd
will not
function properly and will fail to restore paths
automatically when they
recover.  If you have a rolling outage (such as is common
during a
maitenance event) it's likely to leave your system in a case
where all
paths are shows as failed.

Redhat is aware of this issue but has not yet released fixes
publicly.
The current workaround is to disable SElinux (it seems it
has to be
disabled, not just set to permissive) or possibly revert to
older
device-mapper-multipath tools (not sure if this works, but I
don't think
I had this problem until the recent "bugfix"
versions which attempted to
correct problems with root-on-multipath configurations).

Hopefully Redhat will get this critical fix out the door
soon.

Later,
Tom


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