On Sun, Aug 28, 2016 at 12:20:14PM -1000, Brent W. Baccala wrote: > So, there's several problems here: > > 1. libpager can't handle multiple clients > 2. the kernel can't recover from a failed attempt to get a file's memory > object > 3. ext2fs can't cleanly shutdown in this case > > I'm continuing to lobby for a multi-client libpager! I can see that it's > going to raise a lot of locking and concurrency issues, but this program > demonstrates that we've already got problems with the current scheme. Even > a simple multi-client libpager should allow shared read-only access, which > would prevent an unprivileged user from mounting this attack. Root, with > write access to the files in /bin, could still do it, though.
I'm really not seeing the relation between "multiple clients" and "multiple threads". Libpager must be able to handle multiple clients with a single thread, otherwise we don't control scalability and we're back to where we were before Justus' rework... And again, I think it's much easier and much more helpful to change exec and others to _avoid_ mmap, and copy the data in instead, possibly (and in this case probably) with zero-copy. Finally, I fail to see how making libpager handle multiple clients will solve that issue. The only client should be the local kernel, right ? -- Richard Braun
