On 2/2/2016 12:52 PM, Jan Beulich wrote:
NULLing the pointers would cause things like rtc_deinit() to always blow
up when it followed the NULL pointer.
IMO, we should unconditionally always NULL pointers when freeing a
pointer which isn't in local scope. It would make issues such as these
completely obvious.
As would poisoning the pointers, yet poisoning has the advantage
of not allowing PV guests to control what the hypervisor might
access when erroneously de-referencing such a pointer.
Jan
Jan, that sounds interesting. I hope I'm not intruding, but when you
have the time, could you please expand on this?
Besides distinguishing a nuked pointer from zeroed-out memory, I did not
know of any other advantage of 0xDEADBEEF pointer poisoning (generally
or specifically).
How could possibly setting a pointer to NULL allow a PV guest to control
what the hypervisor might access, if the hypervisor *can't access* a
NULL pointer?
And can a PV guest write data @ *hypervisor's* 0 page (virtual and/or
physical)?
Corneliu.
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