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;