Merge branch 'net-sched-fix-remaining-actions-notification-accounting-issues'

Victor Nogueira says:

====================
net/sched: Fix remaining actions notification accounting issues

Commit 8e2efb3f45a5 ("net/sched: add get_fill_size callbacks for actions
missing them") fixed the reported echo/notify skb overrun and noted that
the pre-existing issues Sashiko pointed out [1] would be fixed separately.
This is that series.

Patch 1 makes tcf_action_shared_attrs_size() a real upper bound again.
TCA_ACT_IN_HW_COUNT and TCA_STATS_BASIC_HW are emitted on every action
dump and were never budgeted; TCA_STATS_PKT64 was budgeted once but can be
emitted twice; TCA_ACT_USED_HW_STATS and the rate estimator attributes are
conditional and also unaccounted.

Patch 2 makes the RTM_GETACTION path use the attr_size that tca_action_gd()
already computes and then throws away, so that "tc actions get" can read
back an action whose dump is larger than NLMSG_GOODSIZE.

Patch 3 wraps the reoffload delete notification in
tcf_action_full_attrs_size() like every other notification path, and stops
leaving a skip_sw action installed when that notification cannot be built.

[1] https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260810164357.1653956-1-victor%40mojatatu.com
====================

Link: https://patch.msgid.link/20260824153903.4143642-1-victor@mojatatu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 26 insertions, 11 deletions

diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index b4415d358c91..37eced84dfa5 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 */
@@ -1688,12 +1697,12 @@ out_nlmsg_trim:
 
 static int
 tcf_get_notify(struct net *net, u32 portid, struct nlmsghdr *n,
-	       struct tc_action *actions[], int event,
+	       struct tc_action *actions[], size_t attr_size, int event,
 	       struct netlink_ext_ack *extack)
 {
 	struct sk_buff *skb;
 
-	skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
+	skb = alloc_skb(max(attr_size, NLMSG_GOODSIZE), GFP_KERNEL);
 	if (!skb)
 		return -ENOBUFS;
 	if (tca_get_fill(skb, actions, portid, n->nlmsg_seq, 0, event,
@@ -1858,11 +1867,13 @@ static int tcf_action_delete(struct net *net, struct tc_action *actions[])
 static struct sk_buff *tcf_reoffload_del_notify_msg(struct net *net,
 						    struct tc_action *action)
 {
-	size_t attr_size = tcf_action_fill_size(action);
 	struct tc_action *actions[TCA_ACT_MAX_PRIO] = {
 		[0] = action,
 	};
 	struct sk_buff *skb;
+	size_t attr_size;
+
+	attr_size = tcf_action_full_attrs_size(tcf_action_fill_size(action));
 
 	skb = alloc_skb(max(attr_size, NLMSG_GOODSIZE), GFP_KERNEL);
 	if (!skb)
@@ -1879,15 +1890,18 @@ static struct sk_buff *tcf_reoffload_del_notify_msg(struct net *net,
 static int tcf_reoffload_del_notify(struct net *net, struct tc_action *action)
 {
 	const struct tc_action_ops *ops = action->ops;
-	struct sk_buff *skb;
+	struct sk_buff *skb = NULL;
 	int ret;
 
-	if (!rtnl_notify_needed(net, 0, RTNLGRP_TC)) {
-		skb = NULL;
-	} else {
+	if (rtnl_notify_needed(net, 0, RTNLGRP_TC)) {
 		skb = tcf_reoffload_del_notify_msg(net, action);
+		/* The action has already lost its hardware instance and is
+		 * skip_sw, so it must be released whether or not the
+		 * notification can be built.  Drop the notification rather
+		 * than leave an action behind that processes no packets.
+		 */
 		if (IS_ERR(skb))
-			return PTR_ERR(skb);
+			skb = NULL;
 	}
 
 	ret = tcf_idr_release_unsafe(action);
@@ -2044,7 +2058,8 @@ tca_action_gd(struct net *net, struct nlattr *nla, struct nlmsghdr *n,
 	attr_size = tcf_action_full_attrs_size(attr_size);
 
 	if (event == RTM_GETACTION)
-		ret = tcf_get_notify(net, portid, n, actions, event, extack);
+		ret = tcf_get_notify(net, portid, n, actions, attr_size, event,
+				     extack);
 	else { /* delete */
 		ret = tcf_del_notify(net, n, actions, portid, attr_size, extack);
 		if (ret)