Re: Shared memory DoS's

[stpeters () NETHEAVEN COM (Dick St.Peters)]

Mike Perry writes:

> So as it turns out that it is in fact possible to create a DoS condition by
> requesting a truckload of shared mem, then triggering pagefaults in the entire
> shared region.

Mapped memory segments have been susceptible to this since at least
the early days of VMS, which AFAIK was the first OS to implement
mapped memory (VMS used the term "mapped section").  I ran into this
by accident no later than 1982 while doing image processing on a VMS
system.  My processes run at the lowest possible priority (equivalent
to the highest possible niceness), would effectively shut down the
system until they completed.

VMS didn't have a lot of tools for analyzing what was happening, but a
few experiments quickly showed the culprit was page faulting.  Image
processing tends to step through memory sparsely.

Sorry - I no longer have an exploit :)

--
Dick St.Peters, stpeters () NetHeaven com
Gatekeeper, NetHeaven, Saratoga Springs, NY
Saratoga/Albany/Amsterdam/BoltonLanding/Cobleskill/Greenwich/
GlensFalls/LakePlacid/NorthCreek/Plattsburgh/...
    Oldest Internet service based in the Adirondack-Albany region