Subject: Re: [PATCH ipsec-next v4 5/5] xfrm: add XFRM_MSG_MIGRATE_STATE for single SA migration

From: Steffen Klassert <[email-masked]>
Date: Thu, 22 Jan 2026 11:33:42 +0100

On Mon, Jan 19, 2026 at 09:54:55AM +0100, Antony Antony wrote:
> +
> +static int xfrm_do_migrate_state(struct sk_buff *skb, struct nlmsghdr *nlh,
> +				 struct nlattr **attrs, struct netlink_ext_ack *extack)
> +{
> +	int err = -ESRCH;
> +	struct xfrm_state *x;
> +	struct net *net = sock_net(skb->sk);
> +	struct xfrm_encap_tmpl *encap = NULL;
> +	struct xfrm_user_offload *xuo = NULL;
> +	struct xfrm_migrate m = { .old_saddr.a4 = 0,};
> +	struct xfrm_user_migrate_state *um = nlmsg_data(nlh);
> +
> +	if (!um->id.spi) {
> +		NL_SET_ERR_MSG(extack, "Invalid SPI 0x0");
> +		return -EINVAL;
> +	}
> +
> +	err = copy_from_user_migrate_state(&m, um);
> +	if (err)
> +		return err;
> +
> +	x = xfrm_user_state_lookup(net, &um->id, attrs, &err);
> +
> +	if (x) {
> +		struct xfrm_state *xc;
> +
> +		if (!x->dir) {
> +			NL_SET_ERR_MSG(extack, "State direction is invalid");
> +			err = -EINVAL;
> +			goto error;
> +		}
> +
> +		if (attrs[XFRMA_ENCAP]) {
> +			encap = kmemdup(nla_data(attrs[XFRMA_ENCAP]),
> +					sizeof(*encap), GFP_KERNEL);
> +			if (!encap) {
> +				err = -ENOMEM;
> +				goto error;
> +			}
> +		}
> +		if (attrs[XFRMA_OFFLOAD_DEV]) {
> +			xuo = kmemdup(nla_data(attrs[XFRMA_OFFLOAD_DEV]),
> +				      sizeof(*xuo), GFP_KERNEL);
> +			if (!xuo) {
> +				err = -ENOMEM;
> +				goto error;
> +			}
> +		}
> +		xc = xfrm_state_migrate(x, &m, encap, net, xuo, extack);
> +		if (xc) {
> +			xfrm_state_delete(x);

This xfrm_state_delete() comes too late. You need to synchronize this
with xfrm_state_clone_and_setup() by holding the state lock.
Otherwise we might hand out the same sequence number etc. more than
one time. Unfortunately xfrm_migrate() has the same problem, the
error recovery mechanism in xfrm_migrate() looks broken.