netdev - [PATCH bpf v2] netkit: Reject IFLA_NETKIT_PEER_INFO in netkit_change

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Date: Mon, 27 Nov 2023 21:05:33 +0100
From: Daniel Borkmann <daniel@...earbox.net>
To: martin.lau@...ux.dev
Cc: razor@...ckwall.org,
	bpf@...r.kernel.org,
	netdev@...r.kernel.org,
	Daniel Borkmann <daniel@...earbox.net>,
	Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH bpf v2] netkit: Reject IFLA_NETKIT_PEER_INFO in netkit_change_link

The IFLA_NETKIT_PEER_INFO attribute can only be used during device
creation, but not via changelink callback. Hence reject it there.

Fixes: 35dfaad7188c ("netkit, bpf: Add bpf programmable net device")
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Acked-by: Nikolay Aleksandrov <razor@...ckwall.org>
Cc: Jakub Kicinski <kuba@...nel.org>
---
 v1 -> v2:
   - Switch error code from EACCES to EINVAL (Jakub)

 drivers/net/netkit.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/netkit.c b/drivers/net/netkit.c
index 97bd6705c241..39171380ccf2 100644
--- a/drivers/net/netkit.c
+++ b/drivers/net/netkit.c
@@ -851,6 +851,12 @@ static int netkit_change_link(struct net_device *dev, struct nlattr *tb[],
 		return -EACCES;
 	}
 
+	if (data[IFLA_NETKIT_PEER_INFO]) {
+		NL_SET_ERR_MSG_ATTR(extack, data[IFLA_NETKIT_PEER_INFO],
+				    "netkit peer info cannot be changed after device creation");
+		return -EINVAL;
+	}
+
 	if (data[IFLA_NETKIT_POLICY]) {
 		attr = data[IFLA_NETKIT_POLICY];
 		policy = nla_get_u32(attr);
-- 
2.21.0