[PATCH 42/47] chardev/char-socket: set s->listener = NULL in char_socket_finalize

[Michael Tokarev]

From: Yajun Wu <yajunw@nvidia.com>

After live migration with virtio block device, qemu crash at:

        #0  0x000055914f46f795 in object_dynamic_cast_assert 
(obj=0x559151b7b090, typename=0x55914f80fbc4 "qio-channel", file=0x55914f80fb90 
"/images/testvfe/sw/qemu.gerrit/include/io/channel.h", line=30, 
func=0x55914f80fcb8 <__func__.17257> "QIO_CHANNEL") at ../qom/object.c:872
        #1  0x000055914f480d68 in QIO_CHANNEL (obj=0x559151b7b090) at 
/images/testvfe/sw/qemu.gerrit/include/io/channel.h:29
        #2  0x000055914f4812f8 in qio_net_listener_set_client_func_full 
(listener=0x559151b7a720, func=0x55914f580b97 <tcp_chr_accept>, 
data=0x5591519f4ea0, notify=0x0, context=0x0) at ../io/net-listener.c:166
        #3  0x000055914f580059 in tcp_chr_update_read_handler 
(chr=0x5591519f4ea0) at ../chardev/char-socket.c:637
        #4  0x000055914f583dca in qemu_chr_be_update_read_handlers 
(s=0x5591519f4ea0, context=0x0) at ../chardev/char.c:226
        #5  0x000055914f57b7c9 in qemu_chr_fe_set_handlers_full 
(b=0x559152bf23a0, fd_can_read=0x0, fd_read=0x0, fd_event=0x0, be_change=0x0, 
opaque=0x0, context=0x0, set_open=false, sync_state=true) at 
../chardev/char-fe.c:279
        #6  0x000055914f57b86d in qemu_chr_fe_set_handlers (b=0x559152bf23a0, 
fd_can_read=0x0, fd_read=0x0, fd_event=0x0, be_change=0x0, opaque=0x0, 
context=0x0, set_open=false) at ../chardev/char-fe.c:304
        #7  0x000055914f378caf in vhost_user_async_close (d=0x559152bf21a0, 
chardev=0x559152bf23a0, vhost=0x559152bf2420, cb=0x55914f2fb8c1 
<vhost_user_blk_disconnect>) at ../hw/virtio/vhost-user.c:2725
        #8  0x000055914f2fba40 in vhost_user_blk_event (opaque=0x559152bf21a0, 
event=CHR_EVENT_CLOSED) at ../hw/block/vhost-user-blk.c:395
        #9  0x000055914f58388c in chr_be_event (s=0x5591519f4ea0, 
event=CHR_EVENT_CLOSED) at ../chardev/char.c:61
        #10 0x000055914f583905 in qemu_chr_be_event (s=0x5591519f4ea0, 
event=CHR_EVENT_CLOSED) at ../chardev/char.c:81
        #11 0x000055914f581275 in char_socket_finalize (obj=0x5591519f4ea0) at 
../chardev/char-socket.c:1083
        #12 0x000055914f46f073 in object_deinit (obj=0x5591519f4ea0, 
type=0x5591519055c0) at ../qom/object.c:680
        #13 0x000055914f46f0e5 in object_finalize (data=0x5591519f4ea0) at 
../qom/object.c:694
        #14 0x000055914f46ff06 in object_unref (objptr=0x5591519f4ea0) at 
../qom/object.c:1202
        #15 0x000055914f4715a4 in object_finalize_child_property 
(obj=0x559151b76c50, name=0x559151b7b250 "char3", opaque=0x5591519f4ea0) at 
../qom/object.c:1747
        #16 0x000055914f46ee86 in object_property_del_all (obj=0x559151b76c50) 
at ../qom/object.c:632
        #17 0x000055914f46f0d2 in object_finalize (data=0x559151b76c50) at 
../qom/object.c:693
        #18 0x000055914f46ff06 in object_unref (objptr=0x559151b76c50) at 
../qom/object.c:1202
        #19 0x000055914f4715a4 in object_finalize_child_property 
(obj=0x559151b6b560, name=0x559151b76630 "chardevs", opaque=0x559151b76c50) at 
../qom/object.c:1747
        #20 0x000055914f46ef67 in object_property_del_child 
(obj=0x559151b6b560, child=0x559151b76c50) at ../qom/object.c:654
        #21 0x000055914f46f042 in object_unparent (obj=0x559151b76c50) at 
../qom/object.c:673
        #22 0x000055914f58632a in qemu_chr_cleanup () at ../chardev/char.c:1189
        #23 0x000055914f16c66c in qemu_cleanup () at ../softmmu/runstate.c:830
        #24 0x000055914eee7b9e in qemu_default_main () at ../softmmu/main.c:38
        #25 0x000055914eee7bcc in main (argc=86, argv=0x7ffc97cb8d88) at 
../softmmu/main.c:48

In char_socket_finalize after s->listener freed, event callback function
vhost_user_blk_event will be called to handle CHR_EVENT_CLOSED.
vhost_user_blk_event is calling qio_net_listener_set_client_func_full which
is still using s->listener.

Setting s->listener = NULL after object_unref(OBJECT(s->listener)) can
solve this issue.

Signed-off-by: Yajun Wu <yajunw@nvidia.com>
Acked-by: Jiri Pirko <jiri@nvidia.com>
Message-Id: <20230214021430.3638579-1-yajunw@nvidia.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit b8a7f51f59e28d5a8e0c07ed3919cc9695560ed2)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
---
 chardev/char-socket.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/chardev/char-socket.c b/chardev/char-socket.c
index 879564aa8a..b00efb1482 100644
--- a/chardev/char-socket.c
+++ b/chardev/char-socket.c
@@ -1065,6 +1065,7 @@ static void char_socket_finalize(Object *obj)
         qio_net_listener_set_client_func_full(s->listener, NULL, NULL,
                                               NULL, chr->gcontext);
         object_unref(OBJECT(s->listener));
+        s->listener = NULL;
     }
     if (s->tls_creds) {
         object_unref(OBJECT(s->tls_creds));
-- 
2.30.2