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

[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@fb.com>
Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
---
 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

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

[Yonghong Song]

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;
>   	}
>   
> 

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

[yajun.deng]

July 19, 2021 10:47 PM, "Yonghong Song" <yhs@fb.com> wrote:

> 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);

This is exactly what we need.
> 
> 1 net/core/rtnetlink.c rtnl_notify 734 nlmsg_notify(rtnl, skb, pid, group, report, flags);
> 
It doesn't matter because there is no return value.
 
> 2 net/netfilter/nfnetlink.c nfnetlink_send 176 return nlmsg_notify(nfnlnet->nfnl, skb, portid,
> group, echo, flags);
> 
It only ctnetlink_conntrack_event() use the return value when call nfnetlink_send() in
net/netfilter/nf_conntrack_netlink.c, but it doesn't matter when the return value is ESRCH or zero.

> 3 net/netlink/genetlink.c genl_notify 1506 nlmsg_notify(sk, skb, info->snd_portid, group, report,
> flags);
> 
It doesn't matter because there is no return value.

I think the caller for nlmsg_notify() doesn't need deal with the ESRCH. It also deal with ESRCH
when report variable is not zero.

>> ---
>> 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;
>> }
>>>

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

[Cong Wang]

On Sun, Jul 18, 2021 at 10:19 PM Yajun Deng <yajun.deng@linux.dev> wrote:
> 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.

Looks like the tc-testing failure I saw is also due to this...

Why not just revert the above commit which does not have
much value? It at most saves some instructions.

Thanks.

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

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (refs/heads/master):

On Mon, 19 Jul 2021 13:18:16 +0800 you 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)
> 
> [...]

Here is the summary with links:
  - netlink: Deal with ESRCH error in nlmsg_notify()
    https://git.kernel.org/netdev/net-next/c/fef773fc8110

You are awesome, thank you!
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