[libvirt] [PATCH] CVE-2014-3633: qemu: blkiotune: Use correct definition when looking up disk

[Eric Blake]

On 09/17/2014 10:25 AM, Peter Krempa wrote:
> Live definition was used to look up the disk index while persistent one
> was indexed leading to a crash in qemuDomainGetBlockIoTune. Use the
> correct def and report a nice error.
> 
> Unfortunately it's accessible via read-only connection.
> 

Mitigation - a read-only connection can only crash libvirtd in the cases
where the guest is hot-plugging disks without reflecting those changes
to the persistent definition.  So avoiding hotplug, or doing hotplug
where persistent is always modified alongside live definition, will
avoid the out-of-bounds access.

> Introduced in: eca96694a7f992be633d48d5ca03cedc9bbc3c9aa (v0.9.8)
> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1140724
> Reported-by: Luyao Huang <lhuang at redhat.com>
> Signed-off-by: Peter Krempa <pkrempa at redhat.com>
> ---
>  src/qemu/qemu_driver.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)

ACK. I can write up the libvirt security notice; we'll eventually need
this backported to all the affected maint branches.  I'll coordinate the
backport effort with you on IRC.

> 
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index a5a49ac..209c40e 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -16317,9 +16317,13 @@ qemuDomainGetBlockIoTune(virDomainPtr dom,
>      }
> 
>      if (flags & VIR_DOMAIN_AFFECT_CONFIG) {
> -        int idx = virDomainDiskIndexByName(vm->def, disk, true);
> -        if (idx < 0)
> +        int idx = virDomainDiskIndexByName(persistentDef, disk, true);
> +        if (idx < 0) {
> +            virReportError(VIR_ERR_INVALID_ARG,
> +                           _("disk '%s' was not found in the domain config"),
> +                           disk);
>              goto endjob;
> +        }
>          reply = persistentDef->disks[idx]->blkdeviotune;
>      }
> 

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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