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hw/i386/pc: Fix crash that occurs when introspecting TYPE_PC_MACHINE machines

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QEMU currently crashes when you try to inspect the machines based on
TYPE_PC_MACHINE for their properties:

 $ echo '{ "execute": "qmp_capabilities" }
         { "execute": "qom-list-properties","arguments":
                      { "typename": "pc-q35-10.0-machine"}}' \
   | ./qemu-system-x86_64 -M pc -qmp stdio
 {"QMP": {"version": {"qemu": {"micro": 50, "minor": 2, "major": 9},
  "package": "v9.2.0-1070-g87e115c122-dirty"}, "capabilities": ["oob"]}}
 {"return": {}}
 Segmentation fault (core dumped)

This happens because TYPE_PC_MACHINE machines add a machine_init-
done_notifier in their instance_init function - but instance_init
of machines are not only called for machines that are realized,
but also for machines that are introspected, so in this case the
listener is added for a q35 machine that is never realized. But
since there is already a running pc machine, the listener function
is triggered immediately, causing a crash since it was not for the
right machine it was meant for.

Such listener functions must never be installed from an instance_init
function. Let's do it from pc_basic_device_init() instead - this
function is called from the MachineClass->init() function instead,
i.e. guaranteed to be only called once in the lifetime of a QEMU
process.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2779
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20250117192106.471029-1-thuth@redhat.com>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Thomas Huth 2025-01-17 20:21:06 +01:00 committed by Michael S. Tsirkin
parent f6fc01c786
commit de538288e4
1 changed files with 3 additions and 3 deletions
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6
hw/i386/pc.c
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@ -1241,6 +1241,9 @@ void pc_basic_device_init(struct PCMachineState *pcms,
/* Super I/O */
pc_superio_init(isa_bus, create_fdctrl, pcms->i8042_enabled,
pcms->vmport != ON_OFF_AUTO_ON, &error_fatal);
pcms->machine_done.notify = pc_machine_done;
qemu_add_machine_init_done_notifier(&pcms->machine_done);
}
void pc_nic_init(PCMachineClass *pcmc, ISABus *isa_bus, PCIBus *pci_bus)
@ -1714,9 +1717,6 @@ static void pc_machine_initfn(Object *obj)
if (pcmc->pci_enabled) {
cxl_machine_init(obj, &pcms->cxl_devices_state);
}
pcms->machine_done.notify = pc_machine_done;
qemu_add_machine_init_done_notifier(&pcms->machine_done);
}
static void pc_machine_reset(MachineState *machine, ResetType type)