[libvirt] [PATCH v2] hotplug: Fix libvirtd crash on qemu-attached guest

[John Ferlan]

ping?

Eric/Dan - since you had comments on v1...

Tks,

John
On 09/25/2014 11:00 AM, John Ferlan wrote:
> https://bugzilla.redhat.com/show_bug.cgi?id=1141621
> 
> The crash in this case was because the qemu-attach code did not create
> aliases for qemu cli args. When the detach-interface code was called
> it assumed aliases were set resulting in a core when dereferencing the
> still NULL alias.
> 
> Adding a call to qemuAssignDeviceAliases() resolves the path for
> qemu-attach; however, to prevent future issues an additional check
> for a NULL value is made and an error provided in the deatch path.
> 
> Add some more verbiage to the virsh man page.
> 
> Signed-off-by: John Ferlan <jferlan at redhat.com>
> ---
> 
> v1 is here:
> http://www.redhat.com/archives/libvir-list/2014-September/msg01331.html
> 
> Changes since v1:
>  - Add the call to qemuAssignDeviceAliases() in qemuDomainQemuAttach().
>  - Move the check for NULL alias inside the CAPS_DEVICE check and emit
>    an error rather than trying to remove as an "else" condition.
> 
>  src/qemu/qemu_driver.c  | 3 +++
>  src/qemu/qemu_hotplug.c | 7 +++++++
>  tools/virsh.pod         | 5 +++--
>  3 files changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index 117138a..ef4ecd2 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -14746,6 +14746,9 @@ static virDomainPtr qemuDomainQemuAttach(virConnectPtr conn,
>      if (qemuCanonicalizeMachine(def, qemuCaps) < 0)
>          goto cleanup;
>  
> +    if (qemuAssignDeviceAliases(def, qemuCaps) < 0)
> +        goto cleanup;
> +
>      if (qemuDomainAssignAddresses(def, qemuCaps, NULL) < 0)
>          goto cleanup;
>  
> diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
> index d631887..daebe82 100644
> --- a/src/qemu/qemu_hotplug.c
> +++ b/src/qemu/qemu_hotplug.c
> @@ -3521,6 +3521,13 @@ qemuDomainDetachNetDevice(virConnectPtr conn,
>  
>      qemuDomainObjEnterMonitor(driver, vm);
>      if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_DEVICE)) {
> +        if (!detach->info.alias) {
> +            virReportError(VIR_ERR_OPERATION_FAILED, "%s",
> +                           _("device alias not found: cannot delete the "
> +                             "net device"));
> +            qemuDomainObjExitMonitor(driver, vm);
> +            goto cleanup;
> +        }
>          if (qemuMonitorDelDevice(priv->mon, detach->info.alias) < 0) {
>              qemuDomainObjExitMonitor(driver, vm);
>              virDomainAuditNet(vm, detach, NULL, "detach", false);
> diff --git a/tools/virsh.pod b/tools/virsh.pod
> index eae9195..bd17f68 100644
> --- a/tools/virsh.pod
> +++ b/tools/virsh.pod
> @@ -3698,8 +3698,9 @@ using the UNIX driver. Ideally the process will also have had the
>  
>  Not all functions of libvirt are expected to work reliably after
>  attaching to an externally launched QEMU process. There may be
> -issues with the guest ABI changing upon migration, and hotunplug
> -may not work.
> +issues with the guest ABI changing upon migration and device hotplug
> +or hotunplug may not work. The attached environment should be considered
> +primarily read-only.
>  
>  =item B<qemu-monitor-command> I<domain> { [I<--hmp>] | [I<--pretty>] }
>  I<command>...
>