Bug 729434

Summary:	nfs sillyrename can call d_move without holding the i_mutex
Product:	Red Hat Enterprise Linux 6	Reporter:	Jeff Layton <jlayton>
Component:	kernel	Assignee:	Jeff Layton <jlayton>
Status:	CLOSED ERRATA	QA Contact:	Petr Beňas <pbenas>
Severity:	high	Docs Contact:
Priority:	high
Version:	6.2	CC:	aviro, bfields, dhowells, kzhang, pbenas, pstehlik, rwheeler, sprabhu, steved, yanwang
Target Milestone:	rc
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	kernel-2.6.32-188.el6	Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:
Clones:	729446 (view as bug list)		Environment:
Last Closed:	2011-12-06 14:01:08 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---
Bug Depends On:
Bug Blocks:	729446

Description Jeff Layton 2011-08-09 18:22:26 UTC

As Al pointed out recently, if a process doing a sillyrename ends up getting issued a SIGKILL then it can end up returning back up to userspace while the RENAME operation is still going on the wire. When this happens, it will release the parent's i_mutex prematurely, and nfs_async_rename_done will call d_move without holding the it.

Holding the i_mutex is required to prevent dcache corruption. I sent a patch to Trond to fix this recently by simply unhashing the old and new dentries in this situation, and he has pushed it to Linus for 3.1. I think we'll also want this in 6.2 as well:

commit 73ca1001ed6881b476e8252adcd0eede1ea368ea
Author: Jeff Layton <jlayton@redhat.com>
Date:   Mon Jul 18 11:26:30 2011 -0400

    nfs: don't use d_move in nfs_async_rename_done

Comment 1 RHEL Product and Program Management 2011-08-09 18:40:08 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 3 yanfu,wang 2011-08-12 05:28:09 UTC

hi Jeff,
QE need to know how to reproduce and verify the problem by run some test steps, so could you point out it? thanks.

Comment 4 Jeff Layton 2011-08-12 11:15:31 UTC

There's no reproducer that I'm aware of. This was noticed by inspection. The thing to do here is just to test that sillyrenames still work after the patch. I think the connectathon suite already tests this so making sure that it doesn't regress is probably the best you can do for this.

Comment 5 Kyle McMartin 2011-08-15 12:50:21 UTC

Patch(es) available on kernel-2.6.32-188.el6

Comment 10 errata-xmlrpc 2011-12-06 14:01:08 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