| Message ID | 1531470464-21522-4-git-send-email-thuth@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | Fix crashes with introspection of ARM devices | expand |
On Fri, Jul 13, 2018 at 10:27:31AM +0200, Thomas Huth wrote: > When trying to "device_add bcm2837" on a machine that is not suitable for > this device, you can quickly crash QEMU afterwards, e.g. with "info qtree": > > echo "{'execute':'qmp_capabilities'} {'execute':'device_add', " \ > "'arguments':{'driver':'bcm2837'}} {'execute': 'human-monitor-command', " \ > "'arguments': {'command-line': 'info qtree'}}" | \ > aarch64-softmmu/qemu-system-aarch64 -M integratorcp,accel=qtest -S -qmp stdio > > {"QMP": {"version": {"qemu": {"micro": 50, "minor": 12, "major": 2}, > "package": "build-all"}, "capabilities": []}} > {"return": {}} > {"error": {"class": "GenericError", "desc": "Device 'bcm2837' can not be > hotplugged on this machine"}} > Segmentation fault (core dumped) > > The qdev_set_parent_bus() from instance_init adds a link to the child devices > which is not valid anymore after the bcm2837 instance has been destroyed. > Unfortunately, the child devices do not get destroyed / unlinked correctly > because both object_initialize() and object_property_add_child() increase > the reference count of the child objects by one, but only one reference > is dropped when the parent gets removed. So let's use the new functions > object_initialize_child() and sysbus_init_child_obj() instead to create > the objects, which will take care of creating the child objects with the > correct reference count of one. > > Signed-off-by: Thomas Huth <thuth@redhat.com> Reviewed-by: Eduardo Habkost <ehabkost@redhat.com> The usage of &error_abort in code that can be triggered from device-list-properties still makes me nervous, but that's a separate issue. > --- > hw/arm/bcm2836.c | 18 ++++++------------ > 1 file changed, 6 insertions(+), 12 deletions(-) > > diff --git a/hw/arm/bcm2836.c b/hw/arm/bcm2836.c > index 6805a7d..af97b2f 100644 > --- a/hw/arm/bcm2836.c > +++ b/hw/arm/bcm2836.c > @@ -51,25 +51,19 @@ static void bcm2836_init(Object *obj) > int n; > > for (n = 0; n < BCM283X_NCPUS; n++) { > - object_initialize(&s->cpus[n], sizeof(s->cpus[n]), > - info->cpu_type); > - object_property_add_child(obj, "cpu[*]", OBJECT(&s->cpus[n]), > - &error_abort); > + object_initialize_child(obj, "cpu[*]", &s->cpus[n], sizeof(s->cpus[n]), > + info->cpu_type, &error_abort); > } > > - object_initialize(&s->control, sizeof(s->control), TYPE_BCM2836_CONTROL); > - object_property_add_child(obj, "control", OBJECT(&s->control), NULL); > - qdev_set_parent_bus(DEVICE(&s->control), sysbus_get_default()); > + sysbus_init_child_obj(obj, "control", &s->control, sizeof(s->control), > + TYPE_BCM2836_CONTROL); > > - object_initialize(&s->peripherals, sizeof(s->peripherals), > - TYPE_BCM2835_PERIPHERALS); > - object_property_add_child(obj, "peripherals", OBJECT(&s->peripherals), > - &error_abort); > + sysbus_init_child_obj(obj, "peripherals", &s->peripherals, > + sizeof(s->peripherals), TYPE_BCM2835_PERIPHERALS); > object_property_add_alias(obj, "board-rev", OBJECT(&s->peripherals), > "board-rev", &error_abort); > object_property_add_alias(obj, "vcram-size", OBJECT(&s->peripherals), > "vcram-size", &error_abort); > - qdev_set_parent_bus(DEVICE(&s->peripherals), sysbus_get_default()); > } > > static void bcm2836_realize(DeviceState *dev, Error **errp) > -- > 1.8.3.1 >
On 13.07.2018 23:26, Eduardo Habkost wrote: > On Fri, Jul 13, 2018 at 10:27:31AM +0200, Thomas Huth wrote: >> When trying to "device_add bcm2837" on a machine that is not suitable for >> this device, you can quickly crash QEMU afterwards, e.g. with "info qtree": >> >> echo "{'execute':'qmp_capabilities'} {'execute':'device_add', " \ >> "'arguments':{'driver':'bcm2837'}} {'execute': 'human-monitor-command', " \ >> "'arguments': {'command-line': 'info qtree'}}" | \ >> aarch64-softmmu/qemu-system-aarch64 -M integratorcp,accel=qtest -S -qmp stdio >> >> {"QMP": {"version": {"qemu": {"micro": 50, "minor": 12, "major": 2}, >> "package": "build-all"}, "capabilities": []}} >> {"return": {}} >> {"error": {"class": "GenericError", "desc": "Device 'bcm2837' can not be >> hotplugged on this machine"}} >> Segmentation fault (core dumped) >> >> The qdev_set_parent_bus() from instance_init adds a link to the child devices >> which is not valid anymore after the bcm2837 instance has been destroyed. >> Unfortunately, the child devices do not get destroyed / unlinked correctly >> because both object_initialize() and object_property_add_child() increase >> the reference count of the child objects by one, but only one reference >> is dropped when the parent gets removed. So let's use the new functions >> object_initialize_child() and sysbus_init_child_obj() instead to create >> the objects, which will take care of creating the child objects with the >> correct reference count of one. >> >> Signed-off-by: Thomas Huth <thuth@redhat.com> > > Reviewed-by: Eduardo Habkost <ehabkost@redhat.com> > > The usage of &error_abort in code that can be triggered from > device-list-properties still makes me nervous, but that's a > separate issue. I first had similar thoughts, but I think it's a clear coding issue if the abort triggers here (and not something that the user should normally be able to trigger somehow), so error_abort should be ok in this case. Thomas
On Mon, Jul 16, 2018 at 09:09:13AM +0200, Thomas Huth wrote: > On 13.07.2018 23:26, Eduardo Habkost wrote: > > On Fri, Jul 13, 2018 at 10:27:31AM +0200, Thomas Huth wrote: > >> When trying to "device_add bcm2837" on a machine that is not suitable for > >> this device, you can quickly crash QEMU afterwards, e.g. with "info qtree": > >> > >> echo "{'execute':'qmp_capabilities'} {'execute':'device_add', " \ > >> "'arguments':{'driver':'bcm2837'}} {'execute': 'human-monitor-command', " \ > >> "'arguments': {'command-line': 'info qtree'}}" | \ > >> aarch64-softmmu/qemu-system-aarch64 -M integratorcp,accel=qtest -S -qmp stdio > >> > >> {"QMP": {"version": {"qemu": {"micro": 50, "minor": 12, "major": 2}, > >> "package": "build-all"}, "capabilities": []}} > >> {"return": {}} > >> {"error": {"class": "GenericError", "desc": "Device 'bcm2837' can not be > >> hotplugged on this machine"}} > >> Segmentation fault (core dumped) > >> > >> The qdev_set_parent_bus() from instance_init adds a link to the child devices > >> which is not valid anymore after the bcm2837 instance has been destroyed. > >> Unfortunately, the child devices do not get destroyed / unlinked correctly > >> because both object_initialize() and object_property_add_child() increase > >> the reference count of the child objects by one, but only one reference > >> is dropped when the parent gets removed. So let's use the new functions > >> object_initialize_child() and sysbus_init_child_obj() instead to create > >> the objects, which will take care of creating the child objects with the > >> correct reference count of one. > >> > >> Signed-off-by: Thomas Huth <thuth@redhat.com> > > > > Reviewed-by: Eduardo Habkost <ehabkost@redhat.com> > > > > The usage of &error_abort in code that can be triggered from > > device-list-properties still makes me nervous, but that's a > > separate issue. > > I first had similar thoughts, but I think it's a clear coding issue if > the abort triggers here (and not something that the user should normally > be able to trigger somehow), so error_abort should be ok in this case. Agreed. We don't really have an option, as instance_init can't report errors.
diff --git a/hw/arm/bcm2836.c b/hw/arm/bcm2836.c index 6805a7d..af97b2f 100644 --- a/hw/arm/bcm2836.c +++ b/hw/arm/bcm2836.c @@ -51,25 +51,19 @@ static void bcm2836_init(Object *obj) int n; for (n = 0; n < BCM283X_NCPUS; n++) { - object_initialize(&s->cpus[n], sizeof(s->cpus[n]), - info->cpu_type); - object_property_add_child(obj, "cpu[*]", OBJECT(&s->cpus[n]), - &error_abort); + object_initialize_child(obj, "cpu[*]", &s->cpus[n], sizeof(s->cpus[n]), + info->cpu_type, &error_abort); } - object_initialize(&s->control, sizeof(s->control), TYPE_BCM2836_CONTROL); - object_property_add_child(obj, "control", OBJECT(&s->control), NULL); - qdev_set_parent_bus(DEVICE(&s->control), sysbus_get_default()); + sysbus_init_child_obj(obj, "control", &s->control, sizeof(s->control), + TYPE_BCM2836_CONTROL); - object_initialize(&s->peripherals, sizeof(s->peripherals), - TYPE_BCM2835_PERIPHERALS); - object_property_add_child(obj, "peripherals", OBJECT(&s->peripherals), - &error_abort); + sysbus_init_child_obj(obj, "peripherals", &s->peripherals, + sizeof(s->peripherals), TYPE_BCM2835_PERIPHERALS); object_property_add_alias(obj, "board-rev", OBJECT(&s->peripherals), "board-rev", &error_abort); object_property_add_alias(obj, "vcram-size", OBJECT(&s->peripherals), "vcram-size", &error_abort); - qdev_set_parent_bus(DEVICE(&s->peripherals), sysbus_get_default()); } static void bcm2836_realize(DeviceState *dev, Error **errp)
When trying to "device_add bcm2837" on a machine that is not suitable for this device, you can quickly crash QEMU afterwards, e.g. with "info qtree": echo "{'execute':'qmp_capabilities'} {'execute':'device_add', " \ "'arguments':{'driver':'bcm2837'}} {'execute': 'human-monitor-command', " \ "'arguments': {'command-line': 'info qtree'}}" | \ aarch64-softmmu/qemu-system-aarch64 -M integratorcp,accel=qtest -S -qmp stdio {"QMP": {"version": {"qemu": {"micro": 50, "minor": 12, "major": 2}, "package": "build-all"}, "capabilities": []}} {"return": {}} {"error": {"class": "GenericError", "desc": "Device 'bcm2837' can not be hotplugged on this machine"}} Segmentation fault (core dumped) The qdev_set_parent_bus() from instance_init adds a link to the child devices which is not valid anymore after the bcm2837 instance has been destroyed. Unfortunately, the child devices do not get destroyed / unlinked correctly because both object_initialize() and object_property_add_child() increase the reference count of the child objects by one, but only one reference is dropped when the parent gets removed. So let's use the new functions object_initialize_child() and sysbus_init_child_obj() instead to create the objects, which will take care of creating the child objects with the correct reference count of one. Signed-off-by: Thomas Huth <thuth@redhat.com> --- hw/arm/bcm2836.c | 18 ++++++------------ 1 file changed, 6 insertions(+), 12 deletions(-)