Re: [PATCH] qom-qmp-cmds: fix two memleaks in qmp_object_add

[Igor Mammedov <imammedo@redhat.com>]

On Mon, 9 Mar 2020 17:22:12 +0800
Pan Nengyuan <pannengyuan@huawei.com> wrote:

> 'type/id' forgot to free in qmp_object_add, this patch fix that.
> 
> The leak stack:
> Direct leak of 84 byte(s) in 6 object(s) allocated from:
>     #0 0x7fe2a5ebf768 in __interceptor_malloc (/lib64/libasan.so.5+0xef768)
>     #1 0x7fe2a5044445 in g_malloc (/lib64/libglib-2.0.so.0+0x52445)
>     #2 0x7fe2a505dd92 in g_strdup (/lib64/libglib-2.0.so.0+0x6bd92)
>     #3 0x56344954e692 in qmp_object_add /mnt/sdb/qemu-new/qemu_test/qemu/qom/qom-qmp-cmds.c:258
>     #4 0x563449960f5a in do_qmp_dispatch /mnt/sdb/qemu-new/qemu_test/qemu/qapi/qmp-dispatch.c:132
>     #5 0x563449960f5a in qmp_dispatch /mnt/sdb/qemu-new/qemu_test/qemu/qapi/qmp-dispatch.c:175
>     #6 0x563449498a30 in monitor_qmp_dispatch /mnt/sdb/qemu-new/qemu_test/qemu/monitor/qmp.c:145
>     #7 0x56344949a64f in monitor_qmp_bh_dispatcher /mnt/sdb/qemu-new/qemu_test/qemu/monitor/qmp.c:234
>     #8 0x563449a92a3a in aio_bh_call /mnt/sdb/qemu-new/qemu_test/qemu/util/async.c:136
> 
> Direct leak of 54 byte(s) in 6 object(s) allocated from:
>     #0 0x7fe2a5ebf768 in __interceptor_malloc (/lib64/libasan.so.5+0xef768)
>     #1 0x7fe2a5044445 in g_malloc (/lib64/libglib-2.0.so.0+0x52445)
>     #2 0x7fe2a505dd92 in g_strdup (/lib64/libglib-2.0.so.0+0x6bd92)
>     #3 0x56344954e6c4 in qmp_object_add /mnt/sdb/qemu-new/qemu_test/qemu/qom/qom-qmp-cmds.c:267
>     #4 0x563449960f5a in do_qmp_dispatch /mnt/sdb/qemu-new/qemu_test/qemu/qapi/qmp-dispatch.c:132
>     #5 0x563449960f5a in qmp_dispatch /mnt/sdb/qemu-new/qemu_test/qemu/qapi/qmp-dispatch.c:175
>     #6 0x563449498a30 in monitor_qmp_dispatch /mnt/sdb/qemu-new/qemu_test/qemu/monitor/qmp.c:145
>     #7 0x56344949a64f in monitor_qmp_bh_dispatcher /mnt/sdb/qemu-new/qemu_test/qemu/monitor/qmp.c:234
>     #8 0x563449a92a3a in aio_bh_call /mnt/sdb/qemu-new/qemu_test/qemu/util/async.c:136
> 
> Fixes: 5f07c4d60d091320186e7b0edaf9ed2cc16b2d1e
> Reported-by: Euler Robot <euler.robot@huawei.com>
> Signed-off-by: Pan Nengyuan <pannengyuan@huawei.com>
> ---
>  qom/qom-qmp-cmds.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/qom/qom-qmp-cmds.c b/qom/qom-qmp-cmds.c
> index 49db926fcc..ac59ba1aa8 100644
> --- a/qom/qom-qmp-cmds.c
> +++ b/qom/qom-qmp-cmds.c
> @@ -247,8 +247,8 @@ void qmp_object_add(QDict *qdict, QObject **ret_data, Error **errp)
>      QDict *pdict;
>      Visitor *v;
>      Object *obj;
> -    const char *type;
> -    const char *id;
> +    g_autofree const char *type = NULL;
> +    g_autofree const char *id = NULL;

not sure that's it's correct

qdict_get_try_str() returns the reference to a string within
the QDict, so caller who provided qdict should take care of
freeing it.

>  
>      type = qdict_get_try_str(qdict, "qom-type");
>      if (!type) {