[libvirt] [PATCHv2] conf: fix no error when set an unsupport string in ./devices/shmem/msi[@ioeventfd]

[Luyao Huang]

https://bugzilla.redhat.com/show_bug.cgi?id=1220265

Pass the return value to an enum directly is not safe.
When pass a invalid @ioeventfd and virTristateSwitchTypeFromString
return -1 to def->msi.ioeventfd, and this value transform to
4294967295, so no error when the parse failed.

To fix this issue, folter the value using int and then assign it
to virTristateSwitch as it's done.

Signed-off-by: Luyao Huang <lhuang at redhat.com>
---
v2:
  a new way to fix this issue.

 src/conf/domain_conf.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 4cd36a1..04cce50 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -10847,12 +10847,16 @@ virDomainShmemDefParseXML(xmlNodePtr node,
         }
         VIR_FREE(tmp);
 
-        if ((tmp = virXMLPropString(msi, "ioeventfd")) &&
-            (def->msi.ioeventfd = virTristateSwitchTypeFromString(tmp)) <= 0) {
-            virReportError(VIR_ERR_XML_ERROR,
-                           _("invalid msi ioeventfd setting for shmem: '%s'"),
-                           tmp);
-            goto cleanup;
+        if ((tmp = virXMLPropString(msi, "ioeventfd"))) {
+            int val;
+
+            if ((val = virTristateSwitchTypeFromString(tmp)) <= 0) {
+                virReportError(VIR_ERR_XML_ERROR,
+                               _("invalid msi ioeventfd setting for shmem: '%s'"),
+                               tmp);
+                goto cleanup;
+            }
+            def->msi.ioeventfd = val;
         }
         VIR_FREE(tmp);
     }
-- 
1.8.3.1