vsock: lock down child_ns_mode as write-once

2026-02-26T10:10:03+00:00

Two administrator processes may race when setting child_ns_mode as one process sets child_ns_mode to "local" and then creates a namespace, but another process changes child_ns_mode to "global" between the write and the namespace creation. The first process ends up with a namespace in "global" mode instead of "local". While this can be detected after the fact by reading ns_mode and retrying, it is fragile and error-prone. Make child_ns_mode write-once so that a namespace manager can set it once and be sure it won't change. Writing a different value after the first write returns -EBUSY. This applies to all namespaces, including init_net, where an init process can write "local" to lock all future namespaces into local mode. Fixes: eafb64f40ca4 ("vsock: add netns to vsock core") Suggested-by: Daan De Meyer Suggested-by: Stefano Garzarella Co-developed-by: Stefano Garzarella Signed-off-by: Stefano Garzarella Signed-off-by: Bobby Eshleman Reviewed-by: Stefano Garzarella Link: https://patch.msgid.link/20260223-vsock-ns-write-once-v3-2-c0cde6959923@meta.com Signed-off-by: Paolo Abeni

vsock: add netns to vsock core

2026-01-27T09:45:38+00:00

Add netns logic to vsock core. Additionally, modify transport hook prototypes to be used by later transport-specific patches (e.g., *_seqpacket_allow()). Namespaces are supported primarily by changing socket lookup functions (e.g., vsock_find_connected_socket()) to take into account the socket namespace and the namespace mode before considering a candidate socket a "match". This patch also introduces the sysctl /proc/sys/net/vsock/ns_mode to report the mode and /proc/sys/net/vsock/child_ns_mode to set the mode for new namespaces. Add netns functionality (initialization, passing to transports, procfs, etc...) to the af_vsock socket layer. Later patches that add netns support to transports depend on this patch. This patch changes the allocation of random ports for connectible vsocks in order to avoid leaking the random port range starting point to other namespaces. dgram_allow(), stream_allow(), and seqpacket_allow() callbacks are modified to take a vsk in order to perform logic on namespace modes. In future patches, the net will also be used for socket lookups in these functions. Reviewed-by: Stefano Garzarella Signed-off-by: Bobby Eshleman Link: https://patch.msgid.link/20260121-vsock-vmtest-v16-1-2859a7512097@meta.com Acked-by: Michael S. Tsirkin Signed-off-by: Paolo Abeni

kernel/linux.git/include/net/netns/vsock.h, branch linux-7.0.y

vsock: lock down child_ns_mode as write-once

vsock: add netns to vsock core