Re: [PATCH v6 04/12] Add memory slot versioning and use it to providefast guest write interface

[Avi Kivity]

 On 10/06/2010 10:08 PM, Gleb Natapov wrote:
> >  Malicious userspace can cause entry to be cached, ioctl
> >  SET_USER_MEMORY_REGION 2^32 times, generation number will match,
> >  mark_page_dirty_in_slot will be called with pointer to freed memory.
> >
> Hmm. To zap all cached entires on overflow we need to track them. If we
> will track then we can zap them on each slot update and drop "generation"
> entirely.

To track them you need locking.

Isn't SET_USER_MEMORY_REGION so slow that calling it 2^32 times isn't 
really feasible?

In any case, can use u64 generation count.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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