[PATCH 4.14 102/115] fib_rules: return 0 directly if an exactly same rule exists when NLM_F_EXCL not supplied

[Greg Kroah-Hartman]

From: Hangbin Liu <liuhang...@gmail.com>

[ Upstream commit e9919a24d3022f72bcadc407e73a6ef17093a849 ]

With commit 153380ec4b9 ("fib_rules: Added NLM_F_EXCL support to
fib_nl_newrule") we now able to check if a rule already exists. But this
only works with iproute2. For other tools like libnl, NetworkManager,
it still could add duplicate rules with only NLM_F_CREATE flag, like

[localhost ~ ]# ip rule
0:      from all lookup local
32766:  from all lookup main
32767:  from all lookup default
100000: from 192.168.7.5 lookup 5
100000: from 192.168.7.5 lookup 5

As it doesn't make sense to create two duplicate rules, let's just return
0 if the rule exists.

Fixes: 153380ec4b9 ("fib_rules: Added NLM_F_EXCL support to fib_nl_newrule")
Reported-by: Thomas Haller <thal...@redhat.com>
Signed-off-by: Hangbin Liu <liuhang...@gmail.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@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
@@ -563,9 +563,9 @@ int fib_nl_newrule(struct sk_buff *skb,
                rule->uid_range = fib_kuid_range_unset;
        }
 
-       if ((nlh->nlmsg_flags & NLM_F_EXCL) &&
-           rule_exists(ops, frh, tb, rule)) {
-               err = -EEXIST;
+       if (rule_exists(ops, frh, tb, rule)) {
+               if (nlh->nlmsg_flags & NLM_F_EXCL)
+                       err = -EEXIST;
                goto errout_free;
        }