Re: [PATCH bpf-next v4 1/2] bpf, sockmap: disallow update and delete from tc, xdp, socket_filter and flow_dissector

On Tue, Jun 30, 2026 at 02:54:05PM +0000, Sechang Lim wrote:

sock_map_update_common() and __sock_map_delete() hold stab->lock and call
sock_map_unref() -> sock_map_del_link(), which takes sk_callback_lock for
write. That gives the order stab->lock -> sk_callback_lock.

The reverse order comes from the SK_SKB stream parser.
sk_psock_strp_data_ready() holds sk_callback_lock for read, and after the
verdict tcp_bpf_strp_read_sock() acks the consumed data inline via
__tcp_cleanup_rbuf(). The ACK goes out egress, where a sched_cls program
deletes from the sockmap and takes stab->lock:

 WARNING: possible circular locking dependency detected

[...]

A tc, xdp, socket_filter or flow_dissector program has no reason to
update or delete a sockmap, and redirect does not go through here. Drop
them from may_update_sockmap() so the verifier rejects it. It also
closes the matching sockhash inversion.

Suggested-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Sechang Lim <redacted>
---

Great lets get this merged and we will separately fix the sockops
issue reported by the bots.

Reviewed-by: John Fastabend <john.fastabend@gmail.com>