Bug 892834

Summary:	guestmount: rename() incorrectly follows symbolic links
Product:	Red Hat Enterprise Linux 6	Reporter:	Colin Walters <walters>
Component:	libguestfs	Assignee:	Richard W.M. Jones <rjones>
Status:	CLOSED ERRATA	QA Contact:	Virtualization Bugs <virt-bugs>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	6.5	CC:	bfan, leiwang, wshi
Target Milestone:	rc
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	libguestfs-1.20.9-5.el6	Doc Type:	Bug Fix
Doc Text:	Cause: Renaming a file in guestmount when the target is a symlink. Consequence: guestmount would follow the symlink instead of overwriting it. Fix: A new 'guestfs_rename' API has been added and guestmount now uses it. Result: Renaming a file will overwrite the target.	Story Points:	---
Clone Of:
Clones:	895910 (view as bug list)		Environment:
Last Closed:	2013-11-21 04:42:39 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	895910, 958183
Bug Blocks:

Description Colin Walters 2013-01-07 23:49:26 UTC

Description of problem:

My project ostree implements atomic upgrades by swapping symbolic links.  However, rename() incorrectly follows the symbolic link, instead of overwriting the target.

Version-Release number of selected component (if applicable):

libguestfs-1.16.34-2.el6.x86_64
fuse-2.8.3-4.el6.x86_64
kernel-2.6.32-350.el6.x86_64

How reproducible:

Always.

Expected results (ext4):

$ mkdir adir
$ mkdir bdir
$ ln -s adir current
$ ln -s bdir new
$ mv -T -f new current
$ ls -al
total 16
drwxrwxr-x. 4 walters walters 4096 Jan  7 18:44 .
drwxrwxr-x. 4 walters walters 4096 Jan  7 18:42 ..
drwxrwxr-x. 2 walters walters 4096 Jan  7 18:42 adir
drwxrwxr-x. 2 walters walters 4096 Jan  7 18:42 bdir
lrwxrwxrwx. 1 walters walters    4 Jan  7 18:44 current -> bdir
$ 

Actual results (guestfs):

$ ls -al
total 16
drwxr-xr-x.  2 root root 4096 Jan  7 17:45 .
drwxr-xr-x. 12 root root 4096 Jan  7 17:45 ..
drwxrwxr-x.  2 root root 4096 Jan  7 18:47 adir
drwxrwxr-x.  2 root root 4096 Jan  7 18:46 bdir
lrwxrwxrwx.  1 root root    4 Jan  7 18:46 current -> adir
$ ls -al adir
total 8
drwxrwxr-x. 2 root root 4096 Jan  7 18:47 .
drwxr-xr-x. 4 root root 4096 Jan  7 18:47 ..
lrwxrwxrwx. 1 root root    4 Jan  7 18:46 new -> bdir

(where "new" is a broken symbolic link).

Note to testers: the -T argument to "mv" is important, it will ensure we just use the kernel rename() call instead of following the target.

Comment 3 RHEL Program Management 2013-01-14 06:47:53 UTC

This request was not resolved in time for the current release.
Red Hat invites you to ask your support representative to
propose this request, if still desired, for consideration in
the next release of Red Hat Enterprise Linux.

Comment 4 Richard W.M. Jones 2013-01-21 17:01:38 UTC

Requires the following commits:
https://bugzilla.redhat.com/show_bug.cgi?id=895910#c3

Comment 5 Colin Walters 2013-01-21 17:05:46 UTC

Thanks!  I'll try to get some time to do some testing on the latest Fedora builds (and/or try backporting these myself to RHEL 6.4)

Comment 6 Richard W.M. Jones 2013-06-28 10:55:56 UTC

This is fixed by the rebase (bug 958183).

Comment 12 bfan 2013-07-30 06:37:27 UTC

Verified with libguestfs-1.20.9-6.el6

[root@]# guestmount -a test1.img -m /dev/sda1 /mnt
[root@]# cd /mnt
[root@dhcp-9-42 mnt]# ls
lost+found
[root@dhcp-9-42 mnt]# mkdir adir
[root@dhcp-9-42 mnt]# mkdir bdir
[root@dhcp-9-42 mnt]# ln -s adir current
[root@dhcp-9-42 mnt]# ln -s bdir new
[root@dhcp-9-42 mnt]# mv -T -f new current
[root@dhcp-9-42 mnt]# ls -al
total 19
drwxr-xr-x.  5 root root  1024 Jul 30 22:32 .
dr-xr-xr-x. 28 root root  4096 Jul 29 18:08 ..
drwxr-xr-x.  2 root root  1024 Jul 30 22:31 adir
drwxr-xr-x.  2 root root  1024 Jul 30 22:31 bdir
lrwxrwxrwx.  1 root root     4 Jul 30 22:31 current -> bdir
drwx------.  2 root root 12288 Jul 30 22:30 lost+found

Can get the current link to bdir, so change the status to verfied

Comment 15 errata-xmlrpc 2013-11-21 04:42:39 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-2013-1536.html