[PATCH 4.9 38/44] fib_rules: fix error in backport of e9919a24d302 ("fib_rules: return 0...")

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

When commit e9919a24d302 ("fib_rules: return 0 directly if an exactly
same rule exists when NLM_F_EXCL not supplied") was backported to 4.9.y,
it changed the logic a bit as err should have been reset before exiting
the test, like it happens in the original logic.

If this is not set, errors happen :(

Reported-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
Reported-by: David Ahern <dsahern@xxxxxxxxx>
Reported-by: Florian Westphal <fw@xxxxxxxxx>
Cc: Hangbin Liu <liuhangbin@xxxxxxxxx>
Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/core/fib_rules.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -430,6 +430,7 @@ int fib_nl_newrule(struct sk_buff *skb,
 		goto errout_free;
 
 	if (rule_exists(ops, frh, tb, rule)) {
+		err = 0;
 		if (nlh->nlmsg_flags & NLM_F_EXCL)
 			err = -EEXIST;
 		goto errout_free;