netlink: specs: handshake: do not accept the handler-class sentinel

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"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.

Acked-by: Chuck Lever <cel@kernel.org>
Reviewed-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Link: https://patch.msgid.link/20260904190410.3864660-2-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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This commit is contained in:

Jakub Kicinski 2026-09-04 12:04:10 -07:00

parent f5134d7347

commit fd0291fad9

5 changed files with 9 additions and 5 deletions

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3

Documentation/netlink/specs/handshake.yaml

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5

include/uapi/linux/handshake.h

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2

net/handshake/genl.c

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2

net/handshake/handshake-test.c

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2

net/handshake/request.c

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