https://bugzilla.redhat.com/show_bug.cgi?id=1621910 When introducing this check back in 4ad54a417a1 my mindset was that if an element is missing in update XML then user is requesting for removal of the corresponding setting. For instance, if <bandwidth/> is not present in update XML any QoS previously set on <interface/> is cleared out. Well this assumption is correct but only to some extent. Turns out, we have some lazy users who when updating path to ISO image construct very minimalistic disk XML and pass it to device update API. Such XML is lacking a lot of information, and alias is one of them. This triggers error in virDomainDefCompatibleDevice() because we think that user is requesting to remove the alias. Well, they are not. Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; --- src/conf/domain_conf.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c index 38cac07913..603a4ad652 100644 --- a/src/conf/domain_conf.c +++ b/src/conf/domain_conf.c @@ -28785,9 +28785,9 @@ virDomainDefCompatibleDevice(virDomainDefPtr def, if (action == VIR_DOMAIN_DEVICE_ACTION_UPDATE && live && - ((!!data.newInfo != !!data.oldInfo) || - (data.newInfo && data.oldInfo && - STRNEQ_NULLABLE(data.newInfo->alias, data.oldInfo->alias)))) { + (data.newInfo && data.oldInfo && + data.newInfo->alias && data.oldInfo->alias && + STRNEQ(data.newInfo->alias, data.oldInfo->alias))) { virReportError(VIR_ERR_OPERATION_DENIED, "%s", _("changing device alias is not allowed")); return -1; -- 2.16.4