[PATCH net 1/4] net/sched: act_api: budget all shared attributes in notify skbs

[Victor Nogueira <victor@mojatatu.com>]

tcf_action_shared_attrs_size() is supposed to return an upper bound on the
netlink attributes every action dump emits outside of TCA_ACT_OPTIONS, so
that tcf_add_notify_msg(), tcf_del_notify_msg() and friends can allocate
an skb large enough for the reply.  It has fallen behind the dump path and
is now an underestimate for every single action.

Attributes, such as, TCA_ACT_IN_HW_COUNT and TCA_STATS_BASIC_HW are
emitted unconditionally and never accounted for. TCA_STATS_PKT64,
TCA_ACT_USED_HW_STATS, TCA_STATS_RATE_EST, TCA_STATS_RATE_EST64 require
specific conditions, but are also not accounted for.

Fix the issue by budgeting all of them so that we have a legitimate
upper bound. Even tough for of them require specific conditions, they
are cheap so, to avoid overcomplicating, we opted to account for them
unconditionally as well to account for a real worst case scenario.

Fixes: 4e76e75d6aba ("net sched actions: calculate add/delete event message size")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260810164357.1653956-1-victor%40mojatatu.com
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Victor Nogueira <victor@mojatatu.com>
---
 net/sched/act_api.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index b4415d358c91..766162b0b810 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -443,12 +443,21 @@ static size_t tcf_action_shared_attrs_size(const struct tc_action *act)
 		+ nla_total_size(IFNAMSIZ) /* TCA_ACT_KIND */
 		+ cookie_len /* TCA_ACT_COOKIE */
 		+ nla_total_size(sizeof(struct nla_bitfield32)) /* TCA_ACT_HW_STATS */
+		/* TCA_ACT_USED_HW_STATS */
+		+ nla_total_size(sizeof(struct nla_bitfield32))
+		+ nla_total_size(sizeof(u32)) /* TCA_ACT_IN_HW_COUNT */
 		+ nla_total_size(0) /* TCA_ACT_STATS nested */
 		+ nla_total_size(sizeof(struct nla_bitfield32)) /* TCA_ACT_FLAGS */
 		/* TCA_STATS_BASIC */
 		+ nla_total_size_64bit(sizeof(struct gnet_stats_basic))
-		/* TCA_STATS_PKT64 */
-		+ nla_total_size_64bit(sizeof(u64))
+		/* TCA_STATS_BASIC_HW */
+		+ nla_total_size_64bit(sizeof(struct gnet_stats_basic))
+		/* TCA_STATS_PKT64, emitted by both of the basic copies above */
+		+ 2 * nla_total_size_64bit(sizeof(u64))
+		/* TCA_STATS_RATE_EST */
+		+ nla_total_size_64bit(sizeof(struct gnet_stats_rate_est))
+		/* TCA_STATS_RATE_EST64 */
+		+ nla_total_size_64bit(sizeof(struct gnet_stats_rate_est64))
 		/* TCA_STATS_QUEUE */
 		+ nla_total_size_64bit(sizeof(struct gnet_stats_queue))
 		+ nla_total_size(0) /* TCA_ACT_OPTIONS nested */
-- 
2.55.0