Please re-test it and add some outputs:

# ls -lZ /var/lib/libvirt/images/
# ausearch -m avc -ts recent

I believe it is a problem with labeling.

(In reply to comment #1)

# ll -lZ /var/lib/libvirt/images/
-rw-r--r--  root root system_u:object_r:virt_content_t tmp1.iso
-rw-r--r--  root root system_u:object_r:virt_content_t tmp2.iso


# ausearch -m avc -ts recent
<no matches>

(In reply to comment #1)
> Please re-test it and add some outputs:
> 
> # ls -lZ /var/lib/libvirt/images/
> # ausearch -m avc -ts recent
> 
> I believe it is a problem with labeling.

Please test it in permissive mode. Thanks.

# setenforce 0

Re-test and check AVC messages using ausearch.

(In reply to comment #4)

I re-test it in permissive mode. But the results are the same with Comment 2.

# getenforce 
Permissive

# ll -lZ /var/lib/libvirt/images/
-rw-r--r--  root root system_u:object_r:virt_content_t tmp1.iso
-rw-r--r--  root root system_u:object_r:virt_content_t tmp2.iso

# ausearch -m avc -ts recent
<no matches>

Does it work in permissive mode?

(In reply to comment #6)

It works well in permissive mode.That means if

# setenforce 0
# virsh update-device <guest> cdrom.xml
update successfully

Ok, just turn of dontaudit rules using

# semodule -DB

and also restart auditd daemon

# service auditd restart

Now please repeat the test.

Also please use the latest selinux-policy (-296 release). There is a bug in -293 release which could cause it does not work.

(In reply to comment #9)

Re-test in selinux-policy-296 release in enforcing mode, the same error message will display.

# getenforce
Enforcing

# virsh update-device test cdrom.xml 
error: Failed to update device from cdrom.xml
error: operation failed: could not change media on ide1-cd0: Could not open '/var/lib/libvirt/images/tmp2.iso'

# ll -lZ /var/lib/libvirt/images/
-rw-r--r--  root root system_u:object_r:virt_content_t tmp1.iso
-rw-r--r--  root root system_u:object_r:virt_content_t tmp2.iso

# ausearch -m avc -ts recent
----
time->Fri Dec  3 16:36:08 2010
type=SYSCALL msg=audit(1291365368.585:35): arch=c000003e syscall=59 success=yes exit=0 a0=2b3366c4de80 a1=2b336a84da70 a2=0 a3=0 items=0 ppid=4393 pid=4394 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts1 ses=1 comm="load_policy" exe="/usr/sbin/load_policy" subj=root:system_r:load_policy_t:s0-s0:c0.c1023 key=(null)
type=AVC msg=audit(1291365368.585:35): avc:  denied  { noatsecure } for  pid=4394 comm="load_policy" scontext=root:system_r:semanage_t:s0-s0:c0.c1023 tcontext=root:system_r:load_policy_t:s0-s0:c0.c1023 tclass=process
type=AVC msg=audit(1291365368.585:35): avc:  denied  { rlimitinh } for  pid=4394 comm="load_policy" scontext=root:system_r:semanage_t:s0-s0:c0.c1023 tcontext=root:system_r:load_policy_t:s0-s0:c0.c1023 tclass=process
type=AVC msg=audit(1291365368.585:35): avc:  denied  { siginh } for  pid=4394 comm="load_policy" scontext=root:system_r:semanage_t:s0-s0:c0.c1023 tcontext=root:system_r:load_policy_t:s0-s0:c0.c1023 tclass=process

(In reply to comment #11)
> (In reply to comment #9)
> 
> Re-test in selinux-policy-296 release in enforcing mode, the same error message
> will display.
> 
> # getenforce
> Enforcing

And any chance you get more AVC messages in permissive mode?

Also could you attach your compressed /var/log/audit/audit.log file.

Ok, 
this issue ends up with the following AVC message

type=SYSCALL msg=audit(1291586560.290:56144): arch=c000003e syscall=2 success=no exit=-13 a0=2d5f600 a1=81002 a2=0 a3=40 items=1 ppid=1 pid=32292 auid=4294967295 uid=107 gid=107 euid=107 suid=107 fsuid=107 egid=107 sgid=107 fsgid=107 tty=(none) ses=4294967295 comm="qemu-kvm" exe="/usr/bin/qemu-kvm" subj=system_u:system_r:svirt_t:s0:c569,c812 key=(null)
type=AVC msg=audit(1291586560.290:56144): avc:  denied  { write } for  pid=32292 comm="qemu-kvm" name="tmp2.iso" dev=dm-0 ino=2492610 scontext=system_u:system_r:svirt_t:s0:c569,c812 tcontext=system_u:object_r:virt_content_t:s0 tclass=file

So

#============= svirt_t ==============
allow svirt_t virt_content_t:file write;

which is not allowed.

Virt guys.
could you look at this?

This is a QEMU bug. In the impl of the 'change' command in RHEL5 it always tries to open read-write.

static void do_change_block(const char *device, const char *filename, const char *fmt)
{
  ...
    if (bdrv_open2(bs, filename, BDRV_O_RDWR, drv) != 0) {
  ...
}


In RHEL6 it only tries to open readonly for CDROMs

    bdrv_flags = bdrv_get_type_hint(bs) == BDRV_TYPE_CDROM ? 0 : BDRV_O_RDWR;
    if (bdrv_open(bs, filename, bdrv_flags, drv)) {

The patch from RHEL6 QEMU was

  kvm-block-read-only-open-cdrom-as-read-only-when-using-m.patch
  Upstream commit: cb4e5f8ed1b648c451491b10dc92b1af1e324535
  BZ: 602026

You are right. Afaik there was the same bug also in Fedora.

Thanks.

This could be a duplicate of bug 586173.  Christoph, what do you think?  If it isn't, feel free to assign back to me.

It most likely is.  But I don't want to mark it as duplicate before I have the patch to test it.

Created attachment 473859 [details]
block: read-only: open cdrom as read-only when using monitor's change command

Can you please check if the following patch fixes it?  It's a backport from qemu mainline thas has already landed in RHEL6 as well.

Can you please verify that your issue is fixed with the newest qemu-kvm rpm?

(In reply to comment #22)

Re-test in enforcing mode and found the result is still failed.

# virsh update-device new cdrom.xml 
error: Failed to update device from cdrom.xml
error: operation failed: could not change media on ide1-cd0: Could not open '/var/lib/libvirt/images/tmp2.iso'

# ausearch -m avc -ts recent
...
time->Mon Mar 21 23:07:00 2011
type=SYSCALL msg=audit(1300720020.854:104): arch=c000003e syscall=2 success=no exit=-13 a0=303dc12a64 a1=0 a2=1b6 a3=0 items=0 ppid=3547 pid=5031 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="qemu-kvm" exe="/usr/libexec/qemu-kvm" subj=system_u:system_r:qemu_t:s0-s0:c0.c1023 key=(null)
type=AVC msg=audit(1300720020.854:104): avc:  denied  { read } for  pid=5031 comm="qemu-kvm" name="config" dev=sda3 ino=2491881 scontext=system_u:system_r:qemu_t:s0-s0:c0.c1023 tcontext=system_u:object_r:selinux_config_t:s0 tclass=file


Environment:
# uname -a
Linux localhost.localdomain 2.6.18-237.el5 #1 SMP Mon Dec 13 18:07:57 EST 2010 x86_64 x86_64 x86_64 GNU/Linux
kvm-83-224.el5
libvirt-0.8.2-15.el5
selinux-policy-2.4.6-300.el5

There's not much I can do if the combination of selinux and libvirt's braindead configuration of it prevents you from reopening a CDROM, as it's outside of qemu's control at this point.  Given that it works with a sane qemu config please open a new bug against libvirt for that issue.

> type=AVC msg=audit(1300720020.854:104): avc:  denied  { read } for  pid=5031
> comm="qemu-kvm" name="config" dev=sda3 ino=2491881
> scontext=system_u:system_r:qemu_t:s0-s0:c0.c1023
> tcontext=system_u:object_r:selinux_config_t:s0 tclass=file

That audit log message does not appear to be related to opening of the '/var/lib/libvirt/images/tmp2.iso' file. The I'm guessing  selinux_config_t may well be one of the SELinux policy files itself, probably  the file /etc/selinux/config. Perhaps Miloslav can confirm, but I'd suggest triggering a complete re-label of the entire filesystem.

  touch /.autorelabel

and then reboot the host, and once relabelling completes, repeat your testing of KVM/libvirt again.

Re-test on below environment:
# uname -a
Linux localhost.localdomain 2.6.18-237.el5 #1 SMP Mon Dec 13 18:07:57 EST 2010
x86_64 x86_64 x86_64 GNU/Linux
kvm-83-225.el5
libvirt-0.8.2-15.el5
selinux-policy-2.4.6-300.el5

Steps:
1. # getenforce
  Enforcing

2. # virsh dumpxml new
...
    <disk type='file' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <source file='/var/lib/libvirt/images/tmp1.iso'/>
      <target dev='hdc' bus='ide'/>
      <readonly/>
      <alias name='ide1-cd0'/>
      <address type='drive' controller='0' bus='1' unit='0'/>
    </disk>
...

# virsh start new
Domain new started

In guest, mount this cdrom and check, then umount.

3. Prepare the cdrom xml
# cat cdrom.xml 
  <disk type='file' device='cdrom'>
     <driver name='file'/>
      <source file='/var/lib/libvirt/images/tmp2.iso'/>
      <target dev='hdc' bus='ide'/>
      <readonly/>
    </disk>

4. update device on the fly
# virsh update-device new cdrom.xml 
Device updated successfully

# ausearch -m avc -ts recent
time->Wed Mar 30 00:07:46 2011
type=SYSCALL msg=audit(1301414866.114:639): arch=c000003e syscall=2 success=no exit=-13 a0=303dc12a64 a1=0 a2=1b6 a3=0 items=0 ppid=4594 pid=5187 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=1 comm="qemu-kvm" exe="/usr/libexec/qemu-kvm" subj=root:system_r:qemu_t:s0-s0:c0.c1023 key=(null)
type=AVC msg=audit(1301414866.114:639): avc:  denied  { read } for  pid=5187 comm="qemu-kvm" name="config" dev=sda3 ino=2491881 scontext=root:system_r:qemu_t:s0-s0:c0.c1023 tcontext=system_u:object_r:selinux_config_t:s0 tclass=file

5. But In guest, mount tmp2.iso cdrom, some error will display for the first time mount. Please refer to the attachment. Please help to confirm, thanks

Created attachment 488366 [details]
mount issue

Could you turn off
allow_unconfined_qemu_transition 
And stop running qemu_t in a confined way.

# setsebool -P allow_unconfined_qemu_transition 0
 
Should remove this SELinux protection.

I have no idea why qemu would be trying to read /etc/selinux/config.

(In reply to comment #28)

I have tried to turn off allow_unconfined_qemu_transition,but seems it is not existed in database. 

# getenforce
Enforcing

# setsebool -P allow_unconfined_qemu_transition 0
libsemanage.dbase_llist_set: record not found in the database
libsemanage.dbase_llist_set: could not set record value
Could not change boolean allow_unconfined_qemu_transition
Could not change policy booleans

Also Re-test, the test result is the same as Comment #26.

I think this is a testsuite that is transitioning to qemu_t rather then svirt_t?

Milos, Karel,
could you also try to test this?

*** This bug has been marked as a duplicate of bug 586173 ***