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Re: [Qemu-devel] [PATCH v3 1/6] pc: fix possible NULL pointer dereferenc
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-devel] [PATCH v3 1/6] pc: fix possible NULL pointer dereference in pc_machine_get_device_memory_region_size() |
Date: |
Mon, 27 May 2019 18:36:25 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) |
Igor Mammedov <address@hidden> writes:
> QEMU will crash when device-memory-region-size property is read if
> ms->device_memory
> wasn't initialized yet (ex: property being inspected during preconfig time).
Reproduced:
$ qemu-system-x86_64 -nodefaults -S -display none -preconfig -qmp stdio
{"QMP": {"version": {"qemu": {"micro": 50, "minor": 0, "major": 4},
"package": "v4.0.0-828-ga7b21f6762"}, "capabilities": ["oob"]}}
{"execute": "qmp_capabilities"}
{"return": {}}
{"execute": "qom-get", "arguments": {"path": "/machine", "property":
"device-memory-region-size"}}
Segmentation fault (core dumped)
First time I started looking at this series, I went "I'll need a
reproducer to fully understand what's up, and I don't feel like finding
one now; next series, please". Second time, I had to spend a few
minutes on the reproducer. Wasn't hard, since you provided a clue.
Still: make review easy, include a reproducer whenever you can.
> Instead of crashing return 0 if ms->device_memory hasn't been initialized.
>
> Signed-off-by: Igor Mammedov <address@hidden>
> ---
> hw/i386/pc.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index d98b737..de91e90 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -2461,7 +2461,11 @@ pc_machine_get_device_memory_region_size(Object *obj,
> Visitor *v,
> Error **errp)
> {
> MachineState *ms = MACHINE(obj);
> - int64_t value = memory_region_size(&ms->device_memory->mr);
> + int64_t value = 0;
> +
> + if (ms->device_memory) {
> + memory_region_size(&ms->device_memory->mr);
> + }
>
> visit_type_int(v, name, &value, errp);
> }
This makes qom-get return 0 for the size of memory that doesn't exist,
yet.
A possible alternative would be setting an error.
Opinions?
- [Qemu-devel] [PATCH v3 0/6] numa: deprecate '-numa node, mem' and default memory distribution, Igor Mammedov, 2019/05/17
- [Qemu-devel] [PATCH v3 1/6] pc: fix possible NULL pointer dereference in pc_machine_get_device_memory_region_size(), Igor Mammedov, 2019/05/17
- Re: [Qemu-devel] [PATCH v3 1/6] pc: fix possible NULL pointer dereference in pc_machine_get_device_memory_region_size(),
Markus Armbruster <=
- [Qemu-devel] [PATCH v3 2/6] qmp: make "qom-list-properties" show initial property values, Igor Mammedov, 2019/05/17
- [Qemu-devel] [PATCH v3 3/6] qmp: qmp_qom_list_properties(): ignore empty string options, Igor Mammedov, 2019/05/17
- [Qemu-devel] [PATCH v3 4/6] numa: introduce "numa-mem-supported" machine property, Igor Mammedov, 2019/05/17
- [Qemu-devel] [PATCH v3 5/6] numa: deprecate 'mem' parameter of '-numa node' option, Igor Mammedov, 2019/05/17