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SubjectRe: [PATCH] netlink: Deal with ESRCH error in nlmsg_notify()
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On 7/18/21 10:18 PM, Yajun Deng wrote:
> 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@fb.com>
> Signed-off-by: Yajun Deng <yajun.deng@linux.dev>

Thanks for quick fix. This does fix the bpf selftest issu.
But does this change have negative impacts on other
nlmsg_notify() callers, below 1-3 items?

0 net/core/rtnetlink.c rtnetlink_send 714 return
nlmsg_notify(rtnl, skb, pid, group, echo, GFP_KERNEL);

1 net/core/rtnetlink.c rtnl_notify 734 nlmsg_notify(rtnl, skb,
pid, group, report, flags);

2 net/netfilter/nfnetlink.c nfnetlink_send 176 return
nlmsg_notify(nfnlnet->nfnl, skb, portid, group, echo, flags);

3 net/netlink/genetlink.c genl_notify 1506 nlmsg_notify(sk, skb,
info->snd_portid, group, report, flags);

> ---
> 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;
> }
>
>

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