net/sched: cls_u32: Fix reference counter leak leading to overflow

stable inclusion
from stable-v5.10.185
commit af6eaa57986e82d7efd81984ee607927c6de61e4
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I7N3N2
CVE: CVE-2023-3609

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=af6eaa57986e82d7efd81984ee607927c6de61e4

---------------------------

[ Upstream commit 04c55383 ]

In the event of a failure in tcf_change_indev(), u32_set_parms() will
immediately return without decrementing the recently incremented
reference counter.  If this happens enough times, the counter will
rollover and the reference freed, leading to a double free which can be
used to do 'bad things'.

In order to prevent this, move the point of possible failure above the
point where the reference counter is incremented.  Also save any
meaningful return values to be applied to the return data at the
appropriate point in time.

This issue was caught with KASAN.

Fixes: 705c7091 ("net: sched: cls_u32: no need to call tcf_exts_change for newly allocated struct")
Suggested-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NLee Jones <lee@kernel.org>
Reviewed-by: NEric Dumazet <edumazet@google.com>
Acked-by: NJamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NLu Wei <luwei32@huawei.com>

net/sched/cls_u32.c

@@ -716,12 +716,18 @@ static int u32_set_parms(struct net *net, struct tcf_proto *tp,
 			 struct nlattr *est, bool ovr,
 			 struct netlink_ext_ack *extack)
 {
-	int err;
+	int err, ifindex = -1;
 
 	err = tcf_exts_validate(net, tp, tb, est, &n->exts, ovr, true, extack);
 	if (err < 0)
 		return err;
 
+	if (tb[TCA_U32_INDEV]) {
+		ifindex = tcf_change_indev(net, tb[TCA_U32_INDEV], extack);
+		if (ifindex < 0)
+			return -EINVAL;
+	}
+
 	if (tb[TCA_U32_LINK]) {
 		u32 handle = nla_get_u32(tb[TCA_U32_LINK]);
 		struct tc_u_hnode *ht_down = NULL, *ht_old;
@@ -756,13 +762,9 @@ static int u32_set_parms(struct net *net, struct tcf_proto *tp,
 		tcf_bind_filter(tp, &n->res, base);
 	}
 
-	if (tb[TCA_U32_INDEV]) {
-		int ret;
-		ret = tcf_change_indev(net, tb[TCA_U32_INDEV], extack);
-		if (ret < 0)
-			return -EINVAL;
-		n->ifindex = ret;
-	}
+	if (ifindex >= 0)
+		n->ifindex = ifindex;
+
 	return 0;
 }