On Wed, Apr 28, 2021 at 09:54:16AM +0300, Vasily Averin wrote: > At each login the user forces the kernel to create a new terminal and > allocate up to ~1Kb memory for the tty-related structures. > > By default it's allowed to create up to 4096 ptys with 1024 reserve for > initial mount namespace only and the settings are controlled by host admin. > > Though this default is not enough for hosters with thousands > of containers per node. Host admin can be forced to increase it > up to NR_UNIX98_PTY_MAX = 1<<20. > > By default container is restricted by pty mount_opt.max = 1024, > but admin inside container can change it via remount. As a result, > one container can consume almost all allowed ptys > and allocate up to 1Gb of unaccounted memory. > > It is not enough per-se to trigger OOM on host, however anyway, it allows > to significantly exceed the assigned memcg limit and leads to troubles > on the over-committed node. > > It makes sense to account for them to restrict the host's memory > consumption from inside the memcg-limited container. > > Signed-off-by: Vasily Averin <vvs@xxxxxxxxxxxxx> Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
