releases/5.1.9/revert-fib_rules-return-0-directly-if-an-exactly-same-rule-exists-when-nlm_f_excl-not-supplied.patch

From foo@baz Sun 09 Jun 2019 09:24:16 AM CEST
From: Hangbin Liu <liuhangbin@gmail.com>
Date: Wed, 5 Jun 2019 12:27:14 +0800
Subject: Revert "fib_rules: return 0 directly if an exactly same rule exists when NLM_F_EXCL not supplied"

From: Hangbin Liu <liuhangbin@gmail.com>

[ Upstream commit 4970b42d5c362bf873982db7d93245c5281e58f4 ]

This reverts commit e9919a24d3022f72bcadc407e73a6ef17093a849.

Nathan reported the new behaviour breaks Android, as Android just add
new rules and delete old ones.

If we return 0 without adding dup rules, Android will remove the new
added rules and causing system to soft-reboot.

Fixes: e9919a24d302 ("fib_rules: return 0 directly if an exactly same rule exists when NLM_F_EXCL not supplied")
Reported-by: Nathan Chancellor <natechancellor@gmail.com>
Reported-by: Yaro Slav <yaro330@gmail.com>
Reported-by: Maciej Żenczykowski <zenczykowski@gmail.com>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/core/fib_rules.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -756,9 +756,9 @@ int fib_nl_newrule(struct sk_buff *skb,
 	if (err)
 		goto errout;
 
-	if (rule_exists(ops, frh, tb, rule)) {
-		if (nlh->nlmsg_flags & NLM_F_EXCL)
-			err = -EEXIST;
+	if ((nlh->nlmsg_flags & NLM_F_EXCL) &&
+	    rule_exists(ops, frh, tb, rule)) {
+		err = -EEXIST;
 		goto errout_free;
 	}