[PATCH] netlink: Deal with ESRCH error in nlmsg_notify()

[Yajun Deng]

Yonghong Song report:
The bpf selftest tc_bpf failed with latest bpf-next. 
The following is the command to run and the result:
$ ./test_progs -n 132
[   40.947571] bpf_testmod: loading out-of-tree module taints kernel.
test_tc_bpf:PASS:test_tc_bpf__open_and_load 0 nsec
test_tc_bpf:PASS:bpf_tc_hook_create(BPF_TC_INGRESS) 0 nsec
test_tc_bpf:PASS:bpf_tc_hook_create invalid hook.attach_point 0 nsec
test_tc_bpf_basic:PASS:bpf_obj_get_info_by_fd 0 nsec
test_tc_bpf_basic:PASS:bpf_tc_attach 0 nsec
test_tc_bpf_basic:PASS:handle set 0 nsec
test_tc_bpf_basic:PASS:priority set 0 nsec
test_tc_bpf_basic:PASS:prog_id set 0 nsec
test_tc_bpf_basic:PASS:bpf_tc_attach replace mode 0 nsec
test_tc_bpf_basic:PASS:bpf_tc_query 0 nsec
test_tc_bpf_basic:PASS:handle set 0 nsec
test_tc_bpf_basic:PASS:priority set 0 nsec
test_tc_bpf_basic:PASS:prog_id set 0 nsec
libbpf: Kernel error message: Failed to send filter delete notification
test_tc_bpf_basic:FAIL:bpf_tc_detach unexpected error: -3 (errno 3)
test_tc_bpf:FAIL:test_tc_internal ingress unexpected error: -3 (errno 3)

The failure seems due to the commit
    cfdf0d9ae75b ("rtnetlink: use nlmsg_notify() in rtnetlink_send()")

Deal with ESRCH error in nlmsg_notify() even the report variable is zero.

Reported-by: Yonghong Song <yhs@xxxxxx>
Signed-off-by: Yajun Deng <yajun.deng@xxxxxxxxx>
---
 net/netlink/af_netlink.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 380f95aacdec..24b7cf447bc5 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2545,13 +2545,15 @@ int nlmsg_notify(struct sock *sk, struct sk_buff *skb, u32 portid,
 		/* errors reported via destination sk->sk_err, but propagate
 		 * delivery errors if NETLINK_BROADCAST_ERROR flag is set */
 		err = nlmsg_multicast(sk, skb, exclude_portid, group, flags);
+		if (err == -ESRCH)
+			err = 0;
 	}
 
 	if (report) {
 		int err2;
 
 		err2 = nlmsg_unicast(sk, skb, portid);
-		if (!err || err == -ESRCH)
+		if (!err)
 			err = err2;
 	}
 
-- 
2.32.0