On 3/9/2020 6:15 PM, Daniel P. Berrangé wrote:
> On Mon, Mar 09, 2020 at 10:51:45AM +0100, Igor Mammedov wrote:
>> On Mon, 9 Mar 2020 17:22:12 +0800
>> Pan Nengyuan <pannengy...@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.ro...@huawei.com>
>>> Signed-off-by: Pan Nengyuan <pannengy...@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.
>
> This is correct, but two lines later we have "type = g_strdup(type)".
>
> IOW, the code is storing both a const and non-const string in the
> same variable which is gross.
>
> So there's definitely a leak, but this is also not the right way
> to fix it.
>
> To fix it, notice that g_strdup says
>
> "Duplicates a string. If str is NULL it returns NULL. The
> returned string should be freed with g_free() when no longer
> needed."
>
> IOW, instead of
>
> const char *type;
>
> type = qdict_get_try_str(qdict, "qom-type");
> if (!type) {
> error_setg(errp, QERR_MISSING_PARAMETER, "qom-type");
> return;
> } else {
> type = g_strdup(type);
> qdict_del(qdict, "qom-type");
> }
>
> we want
>
> g_autofree char *type = NULL;
>
> type = g_strdup(qdict_get_try_str(qdict, "qom-type"));
> if (!type) {
> error_setg(errp, QERR_MISSING_PARAMETER, "qom-type");
> return;
> }
>
> qdict_del(qdict, "qom-type");
Good points. Looks very clear.
Thanks.
>
>>> type = qdict_get_try_str(qdict, "qom-type");
>>> if (!type) {
>
>
>
>
> Regards,
> Daniel
>
