netdev - [PATCH net v5 3/5] net: sched: cls_u32: Undo refcount decrement in case update failed

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Date: Thu, 13 Jul 2023 15:05:12 -0300
From: Victor Nogueira <victor@...atatu.com>
To: netdev@...r.kernel.org
Cc: jhs@...atatu.com,
	xiyou.wangcong@...il.com,
	jiri@...nulli.us,
	davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	pctammela@...atatu.com,
	simon.horman@...igine.com,
	kernel@...atatu.com
Subject: [PATCH net v5 3/5] net: sched: cls_u32: Undo refcount decrement in case update failed

In the case of an update, when TCA_U32_LINK is set, u32_set_parms will
decrement the refcount of the ht_down (struct tc_u_hnode) pointer
present in the older u32 filter which we are replacing. However, if
u32_replace_hw_knode errors out, the update command fails and that
ht_down pointer continues decremented. To fix that, when
u32_replace_hw_knode fails, check if ht_down's refcount was decremented
and undo the decrement.

Fixes: d34e3e181395 ("net: cls_u32: Add support for skip-sw flag to tc u32 classifier.")
Signed-off-by: Victor Nogueira <victor@...atatu.com>
Acked-by: Jamal Hadi Salim <jhs@...atatu.com>
Reviewed-by: Pedro Tammela <pctammela@...atatu.com>
Reviewed-by: Simon Horman <simon.horman@...igine.com>
---
 net/sched/cls_u32.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index ed358466d042..5abf31e432ca 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -928,6 +928,13 @@ static int u32_change(struct net *net, struct sk_buff *in_skb,
 		if (err) {
 			u32_unbind_filter(tp, new, tb);
 
+			if (tb[TCA_U32_LINK]) {
+				struct tc_u_hnode *ht_old;
+
+				ht_old = rtnl_dereference(n->ht_down);
+				if (ht_old)
+					ht_old->refcnt++;
+			}
 			__u32_destroy_key(new);
 			return err;
 		}
-- 
2.25.1