--- /dev/null
+From a3d9001b4e287fc043e5539d03d71a32ab114bcb Mon Sep 17 00:00:00 2001
+From: Kai Lueke <kailueke@linux.microsoft.com>
+Date: Thu, 3 Mar 2022 15:55:10 +0100
+Subject: Revert "xfrm: state and policy should fail if XFRMA_IF_ID 0"
+
+From: Kai Lueke <kailueke@linux.microsoft.com>
+
+commit a3d9001b4e287fc043e5539d03d71a32ab114bcb upstream.
+
+This reverts commit 68ac0f3810e76a853b5f7b90601a05c3048b8b54 because ID
+0 was meant to be used for configuring the policy/state without
+matching for a specific interface (e.g., Cilium is affected, see
+https://github.com/cilium/cilium/pull/18789 and
+https://github.com/cilium/cilium/pull/19019).
+
+Signed-off-by: Kai Lueke <kailueke@linux.microsoft.com>
+Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ net/xfrm/xfrm_user.c | 21 +++------------------
+ 1 file changed, 3 insertions(+), 18 deletions(-)
+
+--- a/net/xfrm/xfrm_user.c
++++ b/net/xfrm/xfrm_user.c
+@@ -629,13 +629,8 @@ static struct xfrm_state *xfrm_state_con
+
+ xfrm_smark_init(attrs, &x->props.smark);
+
+- if (attrs[XFRMA_IF_ID]) {
++ if (attrs[XFRMA_IF_ID])
+ x->if_id = nla_get_u32(attrs[XFRMA_IF_ID]);
+- if (!x->if_id) {
+- err = -EINVAL;
+- goto error;
+- }
+- }
+
+ err = __xfrm_init_state(x, false, attrs[XFRMA_OFFLOAD_DEV]);
+ if (err)
+@@ -1371,13 +1366,8 @@ static int xfrm_alloc_userspi(struct sk_
+
+ mark = xfrm_mark_get(attrs, &m);
+
+- if (attrs[XFRMA_IF_ID]) {
++ if (attrs[XFRMA_IF_ID])
+ if_id = nla_get_u32(attrs[XFRMA_IF_ID]);
+- if (!if_id) {
+- err = -EINVAL;
+- goto out_noput;
+- }
+- }
+
+ if (p->info.seq) {
+ x = xfrm_find_acq_byseq(net, mark, p->info.seq);
+@@ -1690,13 +1680,8 @@ static struct xfrm_policy *xfrm_policy_c
+
+ xfrm_mark_get(attrs, &xp->mark);
+
+- if (attrs[XFRMA_IF_ID]) {
++ if (attrs[XFRMA_IF_ID])
+ xp->if_id = nla_get_u32(attrs[XFRMA_IF_ID]);
+- if (!xp->if_id) {
+- err = -EINVAL;
+- goto error;
+- }
+- }
+
+ return xp;
+ error: