On Sat, Feb 25, 2012 at 12:41 AM, Arun Sharma <asharma@xxxxxx> wrote: > On 2/24/12 6:51 AM, Balbir Singh wrote: >> >> On Fri, Feb 24, 2012 at 8:17 AM, KAMEZAWA Hiroyuki >> <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: >>>> >>>> They don't have access to each other's VMAs, but if "accidentally" one >>>> of them comes across an uninitialized page with data from another task, >>>> it's not a violation of the security model. >> >> >> Can you expand more on the single address space model? > > > I haven't thought this through yet. But I know that just adding > > && (cgroup_task_count() == 1) > > to page_needs_clearing() is not going to do it. We'll have to design a new > mechanism (cgroup_mm_count_all()?) and make sure that it doesn't race with > fork() and inadvertently expose pages from the new address space to the > existing one. > > A uid based approach such as the one implemented by Davide Libenzi > > http://thread.gmane.org/gmane.linux.kernel/548928 > http://thread.gmane.org/gmane.linux.kernel/548926 > > would probably apply the optimization to more use cases - but conceptually a > bit more complex. If we go with this more relaxed approach, we'll have to > design a race-free cgroup_uid_count() based mechanism. Are you suggesting all processes with the same UID should have access to each others memory contents? Balbir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href