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From 206abaa45b1c845ef665f2639a8008b04a218165 Mon Sep 17 00:00:00 2001
From: Serhii Popovych <spopovyc@redhat.com>
Date: Mon, 9 Jul 2018 11:31:16 +0200
Subject: [PATCH 200/268] object: fix OBJ_PROP_LINK_UNREF_ON_RELEASE
 ambivalence
MIME-Version: 1.0
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RH-Author: Serhii Popovych <spopovyc@redhat.com>
Message-id: <1531135878-18813-2-git-send-email-spopovyc@redhat.com>
Patchwork-id: 81265
O-Subject: [RHEL-7.6 qemu-kvm-rhev PATCH v2 1/3] object: fix OBJ_PROP_LINK_UNREF_ON_RELEASE ambivalence
Bugzilla: 1556678
RH-Acked-by: Laurent Vivier <lvivier@redhat.com>
RH-Acked-by: Marc-André Lureau <marcandre.lureau@redhat.com>
RH-Acked-by: David Gibson <dgibson@redhat.com>

From: Marc-André Lureau <marcandre.lureau@redhat.com>

A link property can be set during creation, with
object_property_add_link() and later with object_property_set_link().

add_link() doesn't add a reference to the target object, while
set_link() does.

Furthemore, OBJ_PROP_LINK_UNREF_ON_RELEASE flags, set during add_link,
says whether a reference must be released when the property is destroyed.
This can lead to leaks if the property was later set_link(), as the
added reference is never released.

Instead, rename OBJ_PROP_LINK_UNREF_ON_RELEASE to OBJ_PROP_LINK_STRONG
and use that has an indication on how the link handle reference
management in set_link().

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-id: 20180531195119.22021-3-marcandre.lureau@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
(cherry picked from commit 265b578c584b1a86c7028790deaa2f4392dd0a65)
Signed-off-by: Serhii Popovych <spopovyc@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

Conflicts:
	hw/dma/xlnx-zdma.c

This file is missing in 2.12.0.
---
 hw/core/qdev-properties.c |  2 +-
 hw/core/qdev.c            |  2 +-
 hw/display/xlnx_dp.c      |  2 +-
 hw/dma/xilinx_axidma.c    |  4 ++--
 hw/i386/pc.c              |  2 +-
 hw/i386/pc_piix.c         |  2 +-
 hw/i386/pc_q35.c          |  2 +-
 hw/ipmi/ipmi.c            |  2 +-
 hw/net/xilinx_axienet.c   |  4 ++--
 hw/ssi/xilinx_spips.c     |  2 +-
 include/qom/object.h      | 12 +++++++++---
 net/can/can_host.c        |  2 +-
 net/colo-compare.c        |  2 +-
 qom/object.c              |  8 +++++---
 target/arm/cpu.c          |  4 ++--
 ui/console.c              |  2 +-
 16 files changed, 31 insertions(+), 23 deletions(-)

diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c
index 5bbc2d9..f3a83a3 100644
--- a/hw/core/qdev-properties.c
+++ b/hw/core/qdev-properties.c
@@ -1309,7 +1309,7 @@ static void create_link_property(Object *obj, Property *prop, Error **errp)
     object_property_add_link(obj, prop->name, prop->link_type,
                              child,
                              qdev_prop_allow_set_link_before_realize,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              errp);
 }
 
diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index f6f9247..ce7c316 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -435,7 +435,7 @@ void qdev_init_gpio_out_named(DeviceState *dev, qemu_irq *pins,
         object_property_add_link(OBJECT(dev), propname, TYPE_IRQ,
                                  (Object **)&pins[i],
                                  object_property_allow_set_link,
-                                 OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                                 OBJ_PROP_LINK_STRONG,
                                  &error_abort);
         g_free(propname);
     }
diff --git a/hw/display/xlnx_dp.c b/hw/display/xlnx_dp.c
index 6715b9c..b737e1d 100644
--- a/hw/display/xlnx_dp.c
+++ b/hw/display/xlnx_dp.c
@@ -1221,7 +1221,7 @@ static void xlnx_dp_init(Object *obj)
     object_property_add_link(obj, "dpdma", TYPE_XLNX_DPDMA,
                              (Object **) &s->dpdma,
                              xlnx_dp_set_dpdma,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              &error_abort);
 
     /*
diff --git a/hw/dma/xilinx_axidma.c b/hw/dma/xilinx_axidma.c
index 9b48103..401a328 100644
--- a/hw/dma/xilinx_axidma.c
+++ b/hw/dma/xilinx_axidma.c
@@ -525,12 +525,12 @@ static void xilinx_axidma_realize(DeviceState *dev, Error **errp)
     object_property_add_link(OBJECT(ds), "dma", TYPE_XILINX_AXI_DMA,
                              (Object **)&ds->dma,
                              object_property_allow_set_link,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              &local_err);
     object_property_add_link(OBJECT(cs), "dma", TYPE_XILINX_AXI_DMA,
                              (Object **)&cs->dma,
                              object_property_allow_set_link,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              &local_err);
     if (local_err) {
         goto xilinx_axidma_realize_fail;
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 6f686c7..9034f02 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -484,7 +484,7 @@ void pc_cmos_init(PCMachineState *pcms,
                              TYPE_ISA_DEVICE,
                              (Object **)&pcms->rtc,
                              object_property_allow_set_link,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE, &error_abort);
+                             OBJ_PROP_LINK_STRONG, &error_abort);
     object_property_set_link(OBJECT(pcms), OBJECT(s),
                              "rtc_state", &error_abort);
 
diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index 229d551..60441c1 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -290,7 +290,7 @@ static void pc_init1(MachineState *machine,
                                  TYPE_HOTPLUG_HANDLER,
                                  (Object **)&pcms->acpi_dev,
                                  object_property_allow_set_link,
-                                 OBJ_PROP_LINK_UNREF_ON_RELEASE, &error_abort);
+                                 OBJ_PROP_LINK_STRONG, &error_abort);
         object_property_set_link(OBJECT(machine), OBJECT(piix4_pm),
                                  PC_MACHINE_ACPI_DEVICE_PROP, &error_abort);
     }
diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
index e1fd23e..ccdeb11 100644
--- a/hw/i386/pc_q35.c
+++ b/hw/i386/pc_q35.c
@@ -194,7 +194,7 @@ static void pc_q35_init(MachineState *machine)
                              TYPE_HOTPLUG_HANDLER,
                              (Object **)&pcms->acpi_dev,
                              object_property_allow_set_link,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE, &error_abort);
+                             OBJ_PROP_LINK_STRONG, &error_abort);
     object_property_set_link(OBJECT(machine), OBJECT(lpc),
                              PC_MACHINE_ACPI_DEVICE_PROP, &error_abort);
 
diff --git a/hw/ipmi/ipmi.c b/hw/ipmi/ipmi.c
index 9be281f..63c0317 100644
--- a/hw/ipmi/ipmi.c
+++ b/hw/ipmi/ipmi.c
@@ -104,7 +104,7 @@ void ipmi_bmc_find_and_link(Object *obj, Object **bmc)
 {
     object_property_add_link(obj, "bmc", TYPE_IPMI_BMC, bmc,
                              isa_ipmi_bmc_check,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              &error_abort);
 }
 
diff --git a/hw/net/xilinx_axienet.c b/hw/net/xilinx_axienet.c
index d4c2c89..cc880a3 100644
--- a/hw/net/xilinx_axienet.c
+++ b/hw/net/xilinx_axienet.c
@@ -951,12 +951,12 @@ static void xilinx_enet_realize(DeviceState *dev, Error **errp)
     object_property_add_link(OBJECT(ds), "enet", "xlnx.axi-ethernet",
                              (Object **) &ds->enet,
                              object_property_allow_set_link,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              &local_err);
     object_property_add_link(OBJECT(cs), "enet", "xlnx.axi-ethernet",
                              (Object **) &cs->enet,
                              object_property_allow_set_link,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              &local_err);
     if (local_err) {
         goto xilinx_enet_realize_fail;
diff --git a/hw/ssi/xilinx_spips.c b/hw/ssi/xilinx_spips.c
index 426f971..068878c 100644
--- a/hw/ssi/xilinx_spips.c
+++ b/hw/ssi/xilinx_spips.c
@@ -1345,7 +1345,7 @@ static void xlnx_zynqmp_qspips_init(Object *obj)
     object_property_add_link(obj, "stream-connected-dma", TYPE_STREAM_SLAVE,
                              (Object **)&rq->dma,
                              object_property_allow_set_link,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              NULL);
 }
 
diff --git a/include/qom/object.h b/include/qom/object.h
index 96ce81b..fc4555d 100644
--- a/include/qom/object.h
+++ b/include/qom/object.h
@@ -1103,6 +1103,11 @@ char *object_property_get_str(Object *obj, const char *name,
  * @errp: returns an error if this function fails
  *
  * Writes an object's canonical path to a property.
+ *
+ * If the link property was created with
+ * <code>OBJ_PROP_LINK_STRONG</code> bit, the old target object is
+ * unreferenced, and a reference is added to the new target object.
+ *
  */
 void object_property_set_link(Object *obj, Object *value,
                               const char *name, Error **errp);
@@ -1393,7 +1398,7 @@ void object_property_add_child(Object *obj, const char *name,
 
 typedef enum {
     /* Unref the link pointer when the property is deleted */
-    OBJ_PROP_LINK_UNREF_ON_RELEASE = 0x1,
+    OBJ_PROP_LINK_STRONG = 0x1,
 } ObjectPropertyLinkFlags;
 
 /**
@@ -1431,8 +1436,9 @@ void object_property_allow_set_link(const Object *, const char *,
  * link property.  The reference count for <code>*@child</code> is
  * managed by the property from after the function returns till the
  * property is deleted with object_property_del().  If the
- * <code>@flags</code> <code>OBJ_PROP_LINK_UNREF_ON_RELEASE</code> bit is set,
- * the reference count is decremented when the property is deleted.
+ * <code>@flags</code> <code>OBJ_PROP_LINK_STRONG</code> bit is set,
+ * the reference count is decremented when the property is deleted or
+ * modified.
  */
 void object_property_add_link(Object *obj, const char *name,
                               const char *type, Object **child,
diff --git a/net/can/can_host.c b/net/can/can_host.c
index c3d2652..c79347a 100644
--- a/net/can/can_host.c
+++ b/net/can/can_host.c
@@ -77,7 +77,7 @@ static void can_host_instance_init(Object *obj)
     object_property_add_link(obj, "canbus", TYPE_CAN_BUS,
                              (Object **)&ch->bus,
                              object_property_allow_set_link,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              &error_abort);
 }
 
diff --git a/net/colo-compare.c b/net/colo-compare.c
index 23b2d2c..63469b1 100644
--- a/net/colo-compare.c
+++ b/net/colo-compare.c
@@ -980,7 +980,7 @@ static void colo_compare_init(Object *obj)
     object_property_add_link(obj, "iothread", TYPE_IOTHREAD,
                             (Object **)&s->iothread,
                             object_property_allow_set_link,
-                            OBJ_PROP_LINK_UNREF_ON_RELEASE, NULL);
+                            OBJ_PROP_LINK_STRONG, NULL);
 
     s->vnet_hdr = false;
     object_property_add_bool(obj, "vnet_hdr_support", compare_get_vnet_hdr,
diff --git a/qom/object.c b/qom/object.c
index 76a89af..c4f1d36 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -1564,9 +1564,11 @@ static void object_set_link_property(Object *obj, Visitor *v,
         return;
     }
 
-    object_ref(new_target);
     *child = new_target;
-    object_unref(old_target);
+    if (prop->flags == OBJ_PROP_LINK_STRONG) {
+        object_ref(new_target);
+        object_unref(old_target);
+    }
 }
 
 static Object *object_resolve_link_property(Object *parent, void *opaque, const gchar *part)
@@ -1581,7 +1583,7 @@ static void object_release_link_property(Object *obj, const char *name,
 {
     LinkProperty *prop = opaque;
 
-    if ((prop->flags & OBJ_PROP_LINK_UNREF_ON_RELEASE) && *prop->child) {
+    if ((prop->flags & OBJ_PROP_LINK_STRONG) && *prop->child) {
         object_unref(*prop->child);
     }
     g_free(prop);
diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index 4255e9c..9d030e0 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -672,7 +672,7 @@ static void arm_cpu_post_init(Object *obj)
                                  TYPE_MEMORY_REGION,
                                  (Object **)&cpu->secure_memory,
                                  qdev_prop_allow_set_link_before_realize,
-                                 OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                                 OBJ_PROP_LINK_STRONG,
                                  &error_abort);
 #endif
     }
@@ -700,7 +700,7 @@ static void arm_cpu_post_init(Object *obj)
     if (arm_feature(&cpu->env, ARM_FEATURE_M_SECURITY)) {
         object_property_add_link(obj, "idau", TYPE_IDAU_INTERFACE, &cpu->idau,
                                  qdev_prop_allow_set_link_before_realize,
-                                 OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                                 OBJ_PROP_LINK_STRONG,
                                  &error_abort);
         qdev_property_add_static(DEVICE(obj), &arm_cpu_initsvtor_property,
                                  &error_abort);
diff --git a/ui/console.c b/ui/console.c
index 3fb2f4e..594ec63 100644
--- a/ui/console.c
+++ b/ui/console.c
@@ -1280,7 +1280,7 @@ static QemuConsole *new_console(DisplayState *ds, console_type_t console_type,
     object_property_add_link(obj, "device", TYPE_DEVICE,
                              (Object **)&s->device,
                              object_property_allow_set_link,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              &error_abort);
     object_property_add_uint32_ptr(obj, "head",
                                    &s->head, &error_abort);
-- 
1.8.3.1