[PATCH net-next 2/2] netlink: specs: handshake: do not accept the handler-class sentinel
From: Jakub Kicinski <kuba@kernel.org>
Date: 2026-09-04 19:04:17
Subsystem:
handshake upcall for transport layer security, networking [general], the rest, yaml netlink (ynl) · Maintainers:
Chuck Lever, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, Donald Hunter
"max" is the exclusive upper bound of enum handshake_handler_class, not a class a handler can ask for, but the spec lists it as a plain entry. _init_checks() derives the policy limit from the highest entry, so the generated policy came out as NLA_POLICY_MAX(NLA_U32, 2) and handshake_nl_accept_doit() takes class 2 all the way into handshake_req_next(), which walks hn_requests under hn_lock before returning -EAGAIN instead of the -EINVAL a bad class deserves. render-max is how YNL spells this, and unlike a hand written limit it stays correct when a second handler class is added. It does change what HANDSHAKE_HANDLER_CLASS_MAX means - the highest valid class rather than one past it, as in every other Netlink/YNL family - with the count left as __HANDSHAKE_HANDLER_CLASS_MAX. The constant is uAPI, but I could not find any user space user, this constant seems to have been added for kernel's benefit. I think the risk of changing this is worth taking, having MAX with different semantics than the rest of Netlink is very confusing. Signed-off-by: Jakub Kicinski <kuba@kernel.org> --- CC: cel@kernel.org CC: donald.hunter@gmail.com CC: ast@fiberby.net CC: matttbe@kernel.org CC: kernel-tls-handshake@lists.linux.dev --- Documentation/netlink/specs/handshake.yaml | 3 ++- include/uapi/linux/handshake.h | 5 ++++- net/handshake/genl.c | 2 +- net/handshake/handshake-test.c | 2 +- net/handshake/request.c | 2 +- 5 files changed, 9 insertions(+), 5 deletions(-)
diff --git a/Documentation/netlink/specs/handshake.yaml b/Documentation/netlink/specs/handshake.yaml
index 9ab46da04c49..0498ada2dd97 100644
--- a/Documentation/netlink/specs/handshake.yaml
+++ b/Documentation/netlink/specs/handshake.yaml@@ -22,7 +22,8 @@ doc: Netlink protocol to request a transport layer security handshake. type: enum name: handler-class value-start: 0 - entries: [none, tlshd, max] + entries: [none, tlshd] + render-max: true - type: enum name: msg-type
diff --git a/include/uapi/linux/handshake.h b/include/uapi/linux/handshake.h
index d7e40f594888..f907aa082520 100644
--- a/include/uapi/linux/handshake.h
+++ b/include/uapi/linux/handshake.h@@ -13,7 +13,10 @@ enum handshake_handler_class { HANDSHAKE_HANDLER_CLASS_NONE, HANDSHAKE_HANDLER_CLASS_TLSHD, - HANDSHAKE_HANDLER_CLASS_MAX, + + /* private: */ + __HANDSHAKE_HANDLER_CLASS_MAX, + HANDSHAKE_HANDLER_CLASS_MAX = (__HANDSHAKE_HANDLER_CLASS_MAX - 1) }; enum handshake_msg_type {
diff --git a/net/handshake/genl.c b/net/handshake/genl.c
index 58606c2a4600..26e3efec64ca 100644
--- a/net/handshake/genl.c
+++ b/net/handshake/genl.c@@ -14,7 +14,7 @@ /* HANDSHAKE_CMD_ACCEPT - do */ static const struct nla_policy handshake_accept_nl_policy[HANDSHAKE_A_ACCEPT_HANDLER_CLASS + 1] = { - [HANDSHAKE_A_ACCEPT_HANDLER_CLASS] = NLA_POLICY_MAX(NLA_U32, 2), + [HANDSHAKE_A_ACCEPT_HANDLER_CLASS] = NLA_POLICY_MAX(NLA_U32, 1), }; /* HANDSHAKE_CMD_DONE - do */
diff --git a/net/handshake/handshake-test.c b/net/handshake/handshake-test.c
index 3dd507470d5f..4b99acd9f9c7 100644
--- a/net/handshake/handshake-test.c
+++ b/net/handshake/handshake-test.c@@ -42,7 +42,7 @@ static struct handshake_proto handshake_req_alloc_proto_2 = { }; static struct handshake_proto handshake_req_alloc_proto_3 = { - .hp_handler_class = HANDSHAKE_HANDLER_CLASS_MAX, + .hp_handler_class = __HANDSHAKE_HANDLER_CLASS_MAX, }; static struct handshake_proto handshake_req_alloc_proto_4 = {
diff --git a/net/handshake/request.c b/net/handshake/request.c
index cd30d54d0501..ff739ee81cb8 100644
--- a/net/handshake/request.c
+++ b/net/handshake/request.c@@ -115,7 +115,7 @@ struct handshake_req *handshake_req_alloc(const struct handshake_proto *proto, return NULL; if (proto->hp_handler_class <= HANDSHAKE_HANDLER_CLASS_NONE) return NULL; - if (proto->hp_handler_class >= HANDSHAKE_HANDLER_CLASS_MAX) + if (proto->hp_handler_class > HANDSHAKE_HANDLER_CLASS_MAX) return NULL; if (!proto->hp_accept || !proto->hp_done) return NULL;
--
2.55.0