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Bug 656458

Summary:	inode used before security_d_instantiate
Product:	Red Hat Enterprise Linux 6	Reporter:	Eric Paris <eparis>
Component:	kernel	Assignee:	Josef Bacik <jbacik>
Status:	CLOSED ERRATA	QA Contact:	Eryu Guan <eguan>
Severity:	medium	Docs Contact:
Priority:	low
Version:	6.1	CC:	eguan, jbacik, kzhang, rwheeler, walteste
Target Milestone:	rc
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	kernel-2.6.32-175.el6	Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2011-12-06 12:35:35 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 Eric Paris 2010-11-23 19:17:54 UTC

Upstream patch description from Josef:
http://marc.info/?l=linux-kernel&m=129013218025663&w=2

While trying to track down some NFS problems with BTRFS, I kept noticing I was
getting -EACCESS for no apparent reason.  Eric Paris and printk() helped me
figure out that it was SELinux that was giving me grief, with the following
denial

type=AVC msg=audit(1290013638.413:95): avc:  denied  { 0x800000 } for  pid=1772
comm="nfsd" name="" dev=sda1 ino=256 scontext=system_u:system_r:kernel_t:s0
tcontext=system_u:object_r:unlabeled_t:s0 tclass=file

Turns out this is because in d_obtain_alias if we can't find an alias we create
one and do all the normal instantiation stuff, but we don't do the
security_d_instantiate.

Usually we are protected from getting a hashed dentry that hasn't yet run
security_d_instantiate() by the parent's i_mutex, but obviously this isn't an
option there, so in order to deal with the case that a second thread comes in
and finds our new dentry before we get to run security_d_instantiate(), we go
ahead and call it if we find a dentry already.  Eric assures me that this is ok
as the code checks to see if the dentry has been initialized already so calling
security_d_instantiate() against the same dentry multiple times is ok.  With
this patch I'm no longer getting errant -EACCESS values.

Signed-off-by: Josef Bacik <josef>

In RHEL6 we get a slightly different AVC:

type=AVC msg=audit(1289847582.957:112814): avc:  denied  { 0x400000 } for  pid=6055 comm="nfsd" name="" dev=md0 ino=1505857 scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:object_r:unlabeled_t:s0 tclass=file

but it is very likely the same root cause.

Comment 2 RHEL Program Management 2011-01-07 04:22:02 UTC

This request was evaluated by Red Hat Product Management for
inclusion in the current release of Red Hat Enterprise Linux.
Because the affected component is not scheduled to be updated
in the current release, Red Hat is unfortunately unable to
address this request at this time. Red Hat invites you to
ask your support representative to propose this request, if
appropriate and relevant, in the next release of Red Hat
Enterprise Linux. If you would like it considered as an
exception in the current release, please ask your support
representative.

Comment 3 Suzanne Logcher 2011-01-07 16:08:17 UTC

This request was erroneously denied for the current release of Red Hat
Enterprise Linux.  The error has been fixed and this request has been
re-proposed for the current release.

Comment 4 RHEL Program Management 2011-02-01 05:53:02 UTC

This request was evaluated by Red Hat Product Management for
inclusion in the current release of Red Hat Enterprise Linux.
Because the affected component is not scheduled to be updated
in the current release, Red Hat is unfortunately unable to
address this request at this time. Red Hat invites you to
ask your support representative to propose this request, if
appropriate and relevant, in the next release of Red Hat
Enterprise Linux. If you would like it considered as an
exception in the current release, please ask your support
representative.

Comment 5 Ric Wheeler 2011-02-01 14:55:08 UTC

Hi Eric,

Is this still an issue with RHEL6.1?

Comment 6 Eric Paris 2011-02-01 15:01:16 UTC

I believe it is.  Josef?

Comment 7 Josef Bacik 2011-02-01 15:06:12 UTC

Yeah I've not brought it in, waiting for it to land upstream.

Comment 8 RHEL Program Management 2011-02-01 15:08:37 UTC

This request was evaluated by Red Hat Product Management for
inclusion in the current release of Red Hat Enterprise Linux.
Because the affected component is not scheduled to be updated
in the current release, Red Hat is unfortunately unable to
address this request at this time. Red Hat invites you to
ask your support representative to propose this request, if
appropriate and relevant, in the next release of Red Hat
Enterprise Linux. If you would like it considered as an
exception in the current release, please ask your support
representative.

Comment 9 Ric Wheeler 2011-02-01 15:10:38 UTC

How critical is this issue for 6.1? Can it get bumped back to 6.2?

Thanks!

Comment 10 Eric Paris 2011-02-01 15:32:38 UTC

Well, I don't know how hard/easy this is to trigger in the wild.  I know that you need memory pressure on the NFSD server to kick inodes out of cache and you need an open file handle on the client to a directory inode (that was kicked out).  In this situation the server will be unable to perform certain operations on that open handle, such as addname, removename, search, reparent.....

Comment 11 RHEL Program Management 2011-02-01 18:54:00 UTC

This request was erroneously denied for the current release of
Red Hat Enterprise Linux.  The error has been fixed and this
request has been re-proposed for the current release.

Comment 12 RHEL Program Management 2011-05-13 15:25:57 UTC

This request was evaluated by Red Hat Product Management for inclusion
in a Red Hat Enterprise Linux maintenance release. Product Management has 
requested further review of this request by Red Hat Engineering, for potential
inclusion in a Red Hat Enterprise Linux Update release for currently deployed 
products. This request is not yet committed for inclusion in an Update release.

Comment 14 Kyle McMartin 2011-08-01 15:17:11 UTC

Patch(es) available on kernel-2.6.32-175.el6

Comment 18 Eryu Guan 2011-10-20 07:55:00 UTC

I'm unable to reproduce following http://marc.info/?l=linux-fsdevel&m=129035432531716&w=2 on 2.6.32-131.17.1.el6 kernel.

Confirmed patch listed in comment 15 is applied in 2.6.32-206.el6 kernel. -206 kernel also passed fs regression tests

Set SanityOnly

Comment 19 errata-xmlrpc 2011-12-06 12:35:35 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2011-1530.html

Comment 20 Jeff Layton 2012-03-20 18:27:51 UTC

*** Bug 749181 has been marked as a duplicate of this bug. ***