virnetdevtap: Fix memory leak in virNetDevTapReattachBridge

Variable 'master' needs to be free because it will be reassigned in
virNetDevOpenvswitchInterfaceGetMaster().

The leaked stack:
Direct leak of 11 byte(s) in 1 object(s) allocated from:
    #0 0x7f7dad8ba6df in __interceptor_malloc (/lib64/libasan.so.8+0xba6df)
    #1 0x7f7dad715728 in g_malloc (/lib64/libglib-2.0.so.0+0x60728)
    #2 0x7f7dad72d8b2 in g_strdup (/lib64/libglib-2.0.so.0+0x788b2)
    #3 0x7f7dacb63088 in g_strdup_inline /usr/include/glib-2.0/glib/gstrfuncs.h:321
    #4 0x7f7dacb63088 in virNetDevGetName ../src/util/virnetdev.c:823
    #5 0x7f7dacb63886 in virNetDevGetMaster ../src/util/virnetdev.c:909
    #6 0x7f7dacb90288 in virNetDevTapReattachBridge ../src/util/virnetdevtap.c:527
    #7 0x7f7dacd5cd67 in virDomainNetNotifyActualDevice ../src/conf/domain_conf.c:30505
    #8 0x7f7da3a10bc3 in qemuProcessNotifyNets ../src/qemu/qemu_process.c:3290
    #9 0x7f7da3a375c6 in qemuProcessReconnect ../src/qemu/qemu_process.c:9211
    #10 0x7f7dacc0cc53 in virThreadHelper ../src/util/virthread.c:256
    #11 0x7f7dac2875d4 in start_thread (/lib64/libc.so.6+0x875d4)
    #12 0x7f7dac3091bb in __GI___clone3 (/lib64/libc.so.6+0x1091bb)

Fixes: de938b9
Signed-off-by: QiangWei Zhang <[email protected]>
Reviewed-by: Peter Krempa <[email protected]>

Author: QiangWei Zhang

src/util/virnetdevtap.c

@@ -541,6 +541,9 @@ virNetDevTapReattachBridge(const char *tapname,
     /* IFLA_MASTER for a tap on an OVS switch is always "ovs-system" */
     if (STREQ_NULLABLE(master, "ovs-system")) {
         useOVS = true;
+
+        /* master needs to be released here because it will be reassigned */
+        g_clear_pointer(&master, g_free);
         if (virNetDevOpenvswitchInterfaceGetMaster(tapname, &master) < 0)
             return -1;
     }