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Old 10-15-2011, 12:17 AM
Trey Dockendorf
 
Default SELinux triggered during Libvirt snapshots

I recently began getting periodic emails from SEalert that SELinux is
preventing /usr/libexec/qemu-kvm "getattr" access from the directory I store
all my virtual machines for KVM.

All VMs are stored under /vmstore , which is it's own mount point, and
every file and folder under /vmstore currently has the correct context that
was set by doing the following:

semanage fcontext -a -t virt_image_t "/vmstore(/.*)?"
restorecon -R /vmstore

So far I've noticed then when taking snapshots and also when using virsh to
make changes to a domain's XML file. I haven't had any problems for the 3
or 4 months I've run this KVM server using SELinux on Enforcing, and so I'm
not really sure what information is helpful to debug this. The server is
CentOS 6 x86_64 updated to CR. This is the raw audit entry, (hostname
removed)

node=kvmhost.tld type=AVC msg=audit(1318634450.285:28): avc: denied {
getattr } for pid=1842 comm="qemu-kvm" name="/" dev=dm-2 ino=2
scontext=system_u:system_r:svirt_t:s0:c772,c779
tcontext=system_ubject_r:fs_t:s0 tclass=filesystem
node=kvmhost.tld type=SYSCALL msg=audit(1318634450.285:28): arch=c000003e
syscall=138 success=no exit=-13 a0=9 a1=7fff1cf153f0 a2=0 a3=7fff1cf15170
items=0 ppid=1 pid=1842 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/libexec/qemu-kvm"
subj=system_u:system_r:svirt_t:s0:c772,c779 key=(null)

I've attached the alert email as a quote below, (hostname removed)

Any help is greatly appreciated, I've had to deal little with SELinux
fortunately, but at the moment am not really sure if my snapshots are
actually functional or if this is just some false positive.

Thanks
- Trey

Summary
>
> SELinux is preventing /usr/libexec/qemu-kvm "getattr" access on /vmstore.
>
> Detailed Description
>
> SELinux denied access requested by qemu-kvm. It is not expected that this
>> access is required by qemu-kvm and this access may signal an intrusion
>> attempt. It is also possible that the specific version or configuration of
>> the application is causing it to require additional access.
>
> Allowing Access
>
> You can generate a local policy module to allow this access - see FAQ
>> Please file a bug report.
>
> Additional Information
>
> Source Context: system_u:system_r:svirt_t:s0:c772,c779
>
> Target Context: system_ubject_r:fs_t:s0
>
> Target Objects: /vmstore [ filesystem ]
>
> Source: qemu-kvm
>
> Source Path: /usr/libexec/qemu-kvm
>
> Port: <Unknown>
>
> Host: kvmhost.tld
>
> Source RPM Packages: qemu-kvm-0.12.1.2-2.160.el6_1.8
>
> Target RPM Packages:
>
> Policy RPM: selinux-policy-3.7.19-93.el6_1.7
>
> Selinux Enabled: True
>
> Policy Type: targeted
>
> Enforcing Mode: Enforcing
>
> Plugin Name: catchall
>
> Host Name: kvmhost.tld
>
> Platform: Linux kvmhost.tld 2.6.32-71.29.1.el6.x86_64 #1 SMP Mon Jun 27
>> 19:49:27 BST 2011 x86_64 x86_64
>
> Alert Count: 1
>
> First Seen: Fri Oct 14 18:20:50 2011
>
> Last Seen: Fri Oct 14 18:20:50 2011
>
> Local ID: c73c7440-06ee-4611-80ac-712207ef9aa6
>
> Line Numbers:
>
> Raw Audit Messages :
>
>
>> node=kvmhost.tld type=AVC msg=audit(1318634450.285:28): avc: denied {
>> getattr } for pid=1842 comm="qemu-kvm" name="/" dev=dm-2 ino=2
>> scontext=system_u:system_r:svirt_t:s0:c772,c779
>> tcontext=system_ubject_r:fs_t:s0 tclass=filesystem
>
> node=kvmhost.tld type=SYSCALL msg=audit(1318634450.285:28): arch=c000003e
>> syscall=138 success=no exit=-13 a0=9 a1=7fff1cf153f0 a2=0 a3=7fff1cf15170
>> items=0 ppid=1 pid=1842 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/libexec/qemu-kvm"
>> subj=system_u:system_r:svirt_t:s0:c772,c779 key=(null)
>
>
>
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CentOS@centos.org
http://lists.centos.org/mailman/listinfo/centos
 
Old 10-17-2011, 12:47 PM
Daniel J Walsh
 
Default SELinux triggered during Libvirt snapshots

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 10/14/2011 08:17 PM, Trey Dockendorf wrote:
> I recently began getting periodic emails from SEalert that SELinux
> is preventing /usr/libexec/qemu-kvm "getattr" access from the
> directory I store all my virtual machines for KVM.
>
> All VMs are stored under /vmstore , which is it's own mount point,
> and every file and folder under /vmstore currently has the correct
> context that was set by doing the following:
>
> semanage fcontext -a -t virt_image_t "/vmstore(/.*)?" restorecon -R
> /vmstore
>
> So far I've noticed then when taking snapshots and also when using
> virsh to make changes to a domain's XML file. I haven't had any
> problems for the 3 or 4 months I've run this KVM server using
> SELinux on Enforcing, and so I'm not really sure what information
> is helpful to debug this. The server is CentOS 6 x86_64 updated to
> CR. This is the raw audit entry, (hostname removed)
>
> node=kvmhost.tld type=AVC msg=audit(1318634450.285:28): avc: denied
> { getattr } for pid=1842 comm="qemu-kvm" name="/" dev=dm-2 ino=2
> scontext=system_u:system_r:svirt_t:s0:c772,c779
> tcontext=system_ubject_r:fs_t:s0 tclass=filesystem
> node=kvmhost.tld type=SYSCALL msg=audit(1318634450.285:28):
> arch=c000003e syscall=138 success=no exit=-13 a0=9 a1=7fff1cf153f0
> a2=0 a3=7fff1cf15170 items=0 ppid=1 pid=1842 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/libexec/qemu-kvm"
> subj=system_u:system_r:svirt_t:s0:c772,c779 key=(null)
>
> I've attached the alert email as a quote below, (hostname removed)
>
> Any help is greatly appreciated, I've had to deal little with
> SELinux fortunately, but at the moment am not really sure if my
> snapshots are actually functional or if this is just some false
> positive.
>
> Thanks - Trey
>
> Summary
>>
>> SELinux is preventing /usr/libexec/qemu-kvm "getattr" access on
>> /vmstore.
>>
>> Detailed Description
>>
>> SELinux denied access requested by qemu-kvm. It is not expected
>> that this
>>> access is required by qemu-kvm and this access may signal an
>>> intrusion attempt. It is also possible that the specific
>>> version or configuration of the application is causing it to
>>> require additional access.
>>
>> Allowing Access
>>
>> You can generate a local policy module to allow this access - see
>> FAQ
>>> Please file a bug report.
>>
>> Additional Information
>>
>> Source Context: system_u:system_r:svirt_t:s0:c772,c779
>>
>> Target Context: system_ubject_r:fs_t:s0
>>
>> Target Objects: /vmstore [ filesystem ]
>>
>> Source: qemu-kvm
>>
>> Source Path: /usr/libexec/qemu-kvm
>>
>> Port: <Unknown>
>>
>> Host: kvmhost.tld
>>
>> Source RPM Packages: qemu-kvm-0.12.1.2-2.160.el6_1.8
>>
>> Target RPM Packages:
>>
>> Policy RPM: selinux-policy-3.7.19-93.el6_1.7
>>
>> Selinux Enabled: True
>>
>> Policy Type: targeted
>>
>> Enforcing Mode: Enforcing
>>
>> Plugin Name: catchall
>>
>> Host Name: kvmhost.tld
>>
>> Platform: Linux kvmhost.tld 2.6.32-71.29.1.el6.x86_64 #1 SMP
>> Mon Jun 27
>>> 19:49:27 BST 2011 x86_64 x86_64
>>
>> Alert Count: 1
>>
>> First Seen: Fri Oct 14 18:20:50 2011
>>
>> Last Seen: Fri Oct 14 18:20:50 2011
>>
>> Local ID: c73c7440-06ee-4611-80ac-712207ef9aa6
>>
>> Line Numbers:
>>
>> Raw Audit Messages :
>>
>>
>>> node=kvmhost.tld type=AVC msg=audit(1318634450.285:28): avc:
>>> denied { getattr } for pid=1842 comm="qemu-kvm" name="/"
>>> dev=dm-2 ino=2 scontext=system_u:system_r:svirt_t:s0:c772,c779
>>> tcontext=system_ubject_r:fs_t:s0 tclass=filesystem
>>
>> node=kvmhost.tld type=SYSCALL msg=audit(1318634450.285:28):
>> arch=c000003e
>>> syscall=138 success=no exit=-13 a0=9 a1=7fff1cf153f0 a2=0
>>> a3=7fff1cf15170 items=0 ppid=1 pid=1842 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/libexec/qemu-kvm"
>>> subj=system_u:system_r:svirt_t:s0:c772,c779 key=(null)
>>
>>
>>
> _______________________________________________ CentOS mailing
> list CentOS@centos.org
> http://lists.centos.org/mailman/listinfo/centos


THis is a bug in policy. It can be allowed for now.

We have 6.2 selinux-policy preview package available on
http://people.redhat.com/dwalsh/SELinux/RHEL6

I believe all that is happening is qemu-kvm is noticing you have a
file system mounted, and doing a getattr on it.
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