Re: [PATCH] New phys_addr() syscall
Richard Gooch (Richard.Gooch@atnf.CSIRO.AU)
Wed, 22 Jul 1998 11:26:37 +1000
Albert D. Cahalan writes:
> Richard Gooch writes:
> > Albert D. Cahalan writes:
>
> >> There were plans to make mlock() available to normal users for
> >> cryptographic purposes. There would be a quota to protect the
> >> machine. If a user (or group of users) can get 1/32 of the pages
> >> below 16 MB, then the system can not allocate 128 kB for DMA.
> >
> > As I recall, the limit was going to be 1 page per process.
>
> Several pages per user, with the normal system limit.
>
> > In any case, if I want to block DMA buffers, I'll just fork(2) and
> > mlock(2) until I can't do it any more. Not having virt->phys
> > translations isn't going to stop me.
>
> You would be stopped before you grab enough low memory, because you
> would end up with non-DMA memory and hit your limit.
>
> >> In general, it is bad to leak information.
> >
> > There is information leaking going on all over the place. There's
> > little we can do about that. Furthermore, we need to distinguish
> > between levels of sensitivity of information. I think there's very
> > little you can do with virt->phys translations.
>
> Since there may be worse leaks, we should give up?
Since it would be more convenient to have the feature unrestricted,
leave it so. Instead fix the underlying problems, such as moving pages
at mlock(2) time if the system is running low on DMA buffer potential.
Regards,
Richard....
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