On Wed, Nov 15, 2023 at 12:58 AM Casey Schaufler <casey@xxxxxxxxxxxxxxxx> wrote: > > On 11/14/2023 3:59 AM, Yafang Shao wrote: > > On Tue, Nov 14, 2023 at 6:15 PM Michal Hocko <mhocko@xxxxxxxx> wrote: > >> On Mon 13-11-23 11:15:06, Yafang Shao wrote: > >>> On Mon, Nov 13, 2023 at 12:45 AM Casey Schaufler <casey@xxxxxxxxxxxxxxxx> wrote: > >>>> On 11/11/2023 11:34 PM, Yafang Shao wrote: > >>>>> Background > >>>>> ========== > >>>>> > >>>>> In our containerized environment, we've identified unexpected OOM events > >>>>> where the OOM-killer terminates tasks despite having ample free memory. > >>>>> This anomaly is traced back to tasks within a container using mbind(2) to > >>>>> bind memory to a specific NUMA node. When the allocated memory on this node > >>>>> is exhausted, the OOM-killer, prioritizing tasks based on oom_score, > >>>>> indiscriminately kills tasks. This becomes more critical with guaranteed > >>>>> tasks (oom_score_adj: -998) aggravating the issue. > >>>> Is there some reason why you can't fix the callers of mbind(2)? > >>>> This looks like an user space configuration error rather than a > >>>> system security issue. > >>> It appears my initial description may have caused confusion. In this > >>> scenario, the caller is an unprivileged user lacking any capabilities. > >>> While a privileged user, such as root, experiencing this issue might > >>> indicate a user space configuration error, the concerning aspect is > >>> the potential for an unprivileged user to disrupt the system easily. > >>> If this is perceived as a misconfiguration, the question arises: What > >>> is the correct configuration to prevent an unprivileged user from > >>> utilizing mbind(2)?" > >> How is this any different than a non NUMA (mbind) situation? > > In a UMA system, each gigabyte of memory carries the same cost. > > Conversely, in a NUMA architecture, opting to confine processes within > > a specific NUMA node incurs additional costs. In the worst-case > > scenario, if all containers opt to bind their memory exclusively to > > specific nodes, it will result in significant memory wastage. > > That still sounds like you've misconfigured your containers such > that they expect to get more memory than is available, and that > they have more control over it than they really do. And again: What configuration method is suitable to limit user control over memory policy adjustments, besides the heavyweight seccomp approach? -- Regards Yafang
