On Wed, Nov 7, 2018 at 4:00 PM, Michal Hocko [off-list ref] wrote:

On Wed 07-11-18 15:48:20, Daniel Colascione wrote:

quoted

On Tue, Nov 6, 2018 at 1:05 PM, Michal Hocko [off-list ref] wrote:

quoted

otherwise anybody could simply DoS the system
by consuming all available pids.

People can do that today using the instrument of terror widely known
as fork(2). The only thing standing between fork(2) and a full process
table is RLIMIT_NPROC.

not really.

What else, besides memory consumption and (as you mention below)
cgroups? In practice, nobody uses RLIMIT_NPROC, so outside of various
container-y namespaced setups, avoidance of
system-DoS-through-PID-exhaustion isn't a pressing problem.

If you really do care about pid space depletion then you

should use pid cgroup controller.

Or that, sure. But since cgroups are optional, the problem with the
core model remains. In general, if there's a problem X with the core
system API, and you can mitigate X by using a cgroup, X is still a
problem.