Re: fs: sandboxed process brings host down

[Al Viro]

On Fri, Jan 22, 2016 at 10:06:14PM +0100, Dmitry Vyukov wrote:
> Hello,
> 
> While running syzkaller fuzzer I hit the following problem. Supervisor
> process sandboxes worker processes that do random activities with
> CLONE_NEWUSER | CLONE_NEWNS | CLONE_NEWPID | CLONE_NEWUTS |
> CLONE_NEWNET | CLONE_NEWIPC | CLONE_IO, setrlimit, chroot, etc.
> Because of that worker process gains ability to bring whole machine
> down (does not happen without the sandbox).

AFAICS, what you are doing is essentially mount --rbind / / in infinite
loop in luserns.  Which ends up eating all memory.  There's any number
of ways to do the same.  We can play whack-a-mole with them until the
kernel is completely ossified with accounting code of different sorts.
Or one can disable userns and be done with that.