genetlink: use maxattr of 0 for the reject policy

Commit 4fa86555d1cd ("genetlink: piggy back on resv_op to default to
a reject policy") added genl_policy_reject_all to ensure that ops
without an explicit policy reject all attributes rather than silently
accepting them.

The reject policy had maxattr of 1. Passing info->attrs of size 2
may surprise families. Devlink, for instance, assumes that if
info->attrs is set it's safe to access DEVLINK_ATTR_BUS_NAME (1)
and DEVLINK_ATTR_DEV_NAME (2).

Before plugging reject policies into split ops we need to make sure
the genetlink code will not populate info->attrs if family
had no explicit policy for the op.

While even shared code paths within the families can figure out
that given op has no policy fairly easily themselves, passing attrs
with fixed size of 2 feels fairly useless and error prone.

This change has no user-visible impact, reject attrs are not
reported to the user space via getpolicy. We do have to remove
the safety check in netlink_policy_dump_get_policy_idx()
but it seems to have been there to catch likely faulty input,
the code can handle maxattr = 0 just fine.

Link: https://patch.msgid.link/20260311032839.417748-2-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions