Re: [Qemu-block] [PATCH for-2.10 1/4] stubs: Add vm state change handler stubs

[Eric Blake]

On 08/14/2017 11:04 PM, Fam Zheng wrote:
> Signed-off-by: Fam Zheng <address@hidden>

A bit sparse on the 'why' - presumably, upcoming patches will fail to
compile if the stub is not present, but mentioning what dependency this
solves never hurts.

> ---
>  stubs/Makefile.objs          |  1 +
>  stubs/change-state-handler.c | 14 ++++++++++++++
>  2 files changed, 15 insertions(+)
>  create mode 100644 stubs/change-state-handler.c
> 

> +++ b/stubs/change-state-handler.c
> @@ -0,0 +1,14 @@
> +#include "qemu/osdep.h"
> +#include "qemu-common.h"
> +#include "sysemu/sysemu.h"
> +
> +VMChangeStateEntry *qemu_add_vm_change_state_handler(VMChangeStateHandler 
> *cb,
> +                                                     void *opaque)
> +{
> +    return g_malloc0(1);
> +}

Hmm - this is NOT a VMChangeStateEntry; if it ever gets dereferenced,
the caller is (probably) accessing memory out of bounds.  Presumably,
since it is a stub, this should never be called - and if that's the
case, can we just get away with returning NULL instead (I'd rather have
the caller SEGFAULT than dereference out-of-bounds into the heap, if
this stub gets used inappropriately).

> +
> +void qemu_del_vm_change_state_handler(VMChangeStateEntry *e)
> +{
> +    g_free(e);

And of course, if you don't allocate anything, this can be a no-op.

> +}
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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