Linux kernel RDMA core (hw_counters sysfs exposure across network namespaces): RDMA hardware counter sysfs attributes

Impact

RDMA hardware counter sysfs attributes were exposed inside non-initial network namespaces, which is exactly where every containerized tenant lives. The immediate effect is a NULL-pointer oops on read - a tenant in its own netns reads a counter file and takes the node down, killing every co-tenant job on the machine. The structural problem is worse than the crash: device-wide hardware counters are a cross-tenant side channel, since they aggregate traffic from every queue pair on the adapter regardless of which namespace posted it, and this bug is evidence the namespace filter on that surface was not being enforced.

Who can reach it

Local read of the RDMA device's hw_counters sysfs files from inside a non-init network namespace. Any container on an RDMA node.

What to do

Kernel update restoring the init-netns restriction on hw_counters. Until then, mask the RDMA sysfs counter paths out of tenant containers, and treat any fleet-wide RDMA counter dashboard as a surface tenants can read from, not just one you write to.

References