Re: [libvirt] [PATCH 2/2] qemu: add new disk type='lun' for bus='virtio'

As a result of CVE-2011-4127 (see: http://seclists.org/oss-sec/2011/q4/536), qemu (and the kernel) now disable all SG_IO commands on disks via qemu by default. To continue providing this capability to those who specifically ask for it (and hopefully understand the risks), a new libvirt disk type has been created. This new disk type is identical to disk type='block', except that: 1) It is only allowed if bus='virtio' and the qemu version is "new enough" to support it ("new enough" == qemu 0.11 or better), otherwise the domain will fail to start and a CONFIG_UNSUPPORTED error will be logged). 2) The option "scsi=on" will be added to the -device arg to allow SG_IO commands (if type!='lun', "scsi=off" will be added to the -device arg so that SG_IO commands are forbidden). Guests which continue to use disk type='block' will no longer be able to use SG_IO commands on the disk; those that have their disk type changed to type='lun' will still be able to use SG_IO commands.

<dd>If the disk <code>type</code> is "file", then the <code>file</code> attribute specifies the fully-qualified path to the file holding the disk. If the disk - <code>type</code> is "block", then the <code>dev</code> + <code>type</code> is "block" or "lun", then the <code>dev</code> attribute specifies the path to the host device to serve as - the disk. If the disk <code>type</code> is "dir", then the - <code>dir</code> attribute specifies the fully-qualified path - to the directory to use as the disk. If the disk <code>type</code> - is "network", then the <code>protocol</code> attribute specifies - the protocol to access to the requested image; possible values - are "nbd", "rbd", and "sheepdog". If the <code>protocol</code> - attribute is "rbd" or "sheepdog", an additional + the disk ("lun" is only valid if the <code>target + bus="virtio"</code>, and behaves identically to "block", + except that generic SCSI commands from the guest are accepted + in the case of "lun" - also note that <b>you should only use + type='lun' for actual raw devices, never for individual partitions, + or LVM partitions</b>). If the disk <code>type</code> is

+++ b/docs/schemas/domaincommon.rng @@ -779,6 +779,22 @@ </group> <group> <attribute name="type"> + <value>lun</value> + </attribute> + <interleave> + <optional> + <element name="source"> + <attribute name="dev"> + <ref name="absFilePath"/> + </attribute> + <empty/> + </element> + </optional> + <ref name="diskspec"/> + </interleave> + </group> + <group> + <attribute name="type"> <value>dir</value>