cpu: Fix crash with empty -cpu option

Fix the following crash:

  $ qemu-system-x86_64 -cpu ''
  qemu-system-x86_64: qom/cpu.c:291: cpu_class_by_name: \
      Assertion `cpu_model && cc->class_by_name' failed.

Regression test script included.

Fixes: 99193d8f2ef5 ("cpu: drop unnecessary NULL check and cpu_common_class_by_name()")
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <20190418034501.5038-1-ehabkost@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Tested-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/exec.c b/exec.c
index 08f6cafcbc..f7f3cdbf4a 100644
--- a/exec.c
+++ b/exec.c
@@ -991,6 +991,10 @@ const char *parse_cpu_option(const char *cpu_option)
     const char *cpu_type;
 
     model_pieces = g_strsplit(cpu_option, ",", 2);
+    if (!model_pieces[0]) {
+        error_report("-cpu option cannot be empty");
+        exit(1);
+    }
 
     oc = cpu_class_by_name(CPU_RESOLVING_TYPE, model_pieces[0]);
     if (oc == NULL) {