Re: [Qemu-devel] [PATCH 0/2] object_initialize: check size of passed in memory

[Andreas Färber]

Am 23.08.2013 15:38, schrieb Peter Maydell:
> This patchset addresses a concern that came up with Andreas' recent
> patches for using embedded objects in some of the ARM CPU devices:
> object_initialize() doesn't check that there's actually enough space
> for the type being added, so if you have:
> 
> struct MyDevice {
>    ...
>    SomeObject obj;
> };
> 
>     object_initialize(&mydev->obj, "some-object");
> 
> then there's no compile time or runtime check that SomeObject
> is really big enough for the "some-object" object -- if the
> implementation is changed later then there will be silent
> memory corruption.
> 
> These patches make object_initialize() a macro which can then
> use sizeof(*PTR) to pass the size into the implementation to
> be checked.

Based on your comment I was already preparing a patch to add an explicit
size argument - there's only 33 users in qemu.git, and it would cover
qbus_create_inplace() and other indirect users as well.

> The virtio patch is worth applying anyway -- it removes some
> pointless casts which would otherwise have caused false
> positives.

Agreed. We shouldn't cast objects before they're initialized. That
OBJECT() is a no-op today I would consider an implementation detail.

Regards,
Andreas

> 
> Disclaimer: I've eyeballed all the uses of object_initialize()
> but I haven't necessarily tested them all.
> 
> Peter Maydell (2):
>   virtio: Remove unnecessary OBJECT casts
>   qom: Make object_initialize and object_initialize_with_type check
>     size
> 
>  hw/core/qdev.c             |    2 +-
>  hw/s390x/s390-virtio-bus.c |   12 ++++++------
>  hw/s390x/virtio-ccw.c      |   14 +++++++-------
>  hw/virtio/virtio-pci.c     |   16 ++++++++--------
>  include/qom/object.h       |   36 ++++++++++++++++++++++++++++++++++--
>  qom/object.c               |    9 +++++----
>  6 files changed, 61 insertions(+), 28 deletions(-)
> 


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