Re: [syzbot ci] Re: net: move netdev_compute_master_upper_features to ndo_set_features

[Paolo Abeni <pabeni@redhat.com>]

On 3/12/26 4:58 PM, Sabrina Dubroca wrote:
> 2026-03-12, 14:34:44 +0000, Hangbin Liu wrote:
>> On Thu, Mar 12, 2026 at 12:13:52PM +0100, Sabrina Dubroca wrote:
>>> Proper fix (so that the notification we're sending during
>>> upper_dev_link has full linkinfo) would be to move
>>> netdev_upper_dev_link() to after macsec_changelink_common() and fix up
>>> the error handling. I don't see anything in macsec_add_dev or
>>> macsec_changelink_common that needs the device to be linked. But
>>
>> If we move the netdev_upper_dev_link() after macsec_changelink_common(),
>> we will not goto nla_put_failure via default, right?
> 
> Yes.
> 
>>> anyway it doesn't make sense for macsec_fill_info to return -EMSGSIZE
>>> on invalid data, so the "bandaid" should be included as well.
>>>
>>> Should this be part of this series (either just the "bandaid" or the
>>> "proper fix"+bandaid), since we never saw a problem before?
>>
>> Since macsec need the "bandaid" fix either way. How about you post the
>> "bandaid" fix to net. And I include the "proper fix" in this series for
>> net-next?
> 
> But I don't think it's needed in net. Am I missing a codepath (before
> your series) where macsec_fill_info could be called for the new device
> before macsec_newlink returns? If not, it doesn't really qualify as a
> fix, that's why I was asking Paolo.

FWIW, I don't see a codepath calling into rtmsg_ifinfo_build_skb()
before device initialization, so I would be fine targeting net-next with
the EMSGSIZE-related change.

Side note, it looks like that the WARN() in the rnnetlink code here
helped identifying a real problem and correctly returning 0 when the
key_len is not yet initialized will silence it forever, what about
preserving a warning for this kind of race? something alike:

---
diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
index f6cad0746a02..82974d4fa3f6 100644
--- a/drivers/net/macsec.c
+++ b/drivers/net/macsec.c
@@ -4337,7 +4337,8 @@ static int macsec_fill_info(struct sk_buff *skb,
 		csid = secy->xpn ? MACSEC_CIPHER_ID_GCM_AES_XPN_256 :
MACSEC_CIPHER_ID_GCM_AES_256;
 		break;
 	default:
-		goto nla_put_failure;
+		WARN_ON_ONCE(1);
+		return 0;
 	}