[Qemu-devel] [PATCH v2] net: Fix a potential segfault

[Lin Ma <lma@suse.com>]

If user forgets to provide any backend types for '-netdev' in qemu CLI,
It triggers seg fault.

e.g.

Expected:
$ qemu -netdev id=net0
qemu-system-x86_64: Parameter 'type' is missing

Actual:
$ qemu -netdev id=net0
Segmentation fault (core dumped)

Signed-off-by: Lin Ma <lma@suse.com>
---
 net/net.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/net/net.c b/net/net.c
index efb9eaf779..f89790be4a 100644
--- a/net/net.c
+++ b/net/net.c
@@ -1093,9 +1093,12 @@ static int net_client_init(QemuOpts *opts, bool is_netdev, Error **errp)
     int ret = -1;
     Visitor *v = opts_visitor_new(opts);
 
-    if (is_netdev && is_help_option(qemu_opt_get(opts, "type"))) {
-        show_netdevs();
-        exit(0);
+    if (is_netdev) {
+        const char *type = qemu_opt_get(opts, "type");
+        if (type && is_help_option(type)) {
+            show_netdevs();
+            exit(0);
+        }
     } else {
         /* Parse convenience option format ip6-net=fec0::0[/64] */
         const char *ip6_net = qemu_opt_get(opts, "ipv6-net");
-- 
2.16.2