xfrm: Check if_id in xfrm_migrate

This patch enables distinguishing SAs and SPs based on if_id during
the xfrm_migrate flow. This ensures support for xfrm interfaces
throughout the SA/SP lifecycle.

When there are multiple existing SPs with the same direction,
the same xfrm_selector and different endpoint addresses,
xfrm_migrate might fail with ENODATA.

Specifically, the code path for performing xfrm_migrate is:
  Stage 1: find policy to migrate with
    xfrm_migrate_policy_find(sel, dir, type, net)
  Stage 2: find and update state(s) with
    xfrm_migrate_state_find(mp, net)
  Stage 3: update endpoint address(es) of template(s) with
    xfrm_policy_migrate(pol, m, num_migrate)

Currently "Stage 1" always returns the first xfrm_policy that
matches, and "Stage 3" looks for the xfrm_tmpl that matches the
old endpoint address. Thus if there are multiple xfrm_policy
with same selector, direction, type and net, "Stage 1" might
rertun a wrong xfrm_policy and "Stage 3" will fail with ENODATA
because it cannot find a xfrm_tmpl with the matching endpoint
address.

The fix is to allow userspace to pass an if_id and add if_id
to the matching rule in Stage 1 and Stage 2 since if_id is a
unique ID for xfrm_policy and xfrm_state. For compatibility,
if_id will only be checked if the attribute is set.

Tested with additions to Android's kernel unit test suite:
https://android-review.googlesource.com/c/kernel/tests/+/1668886

Signed-off-by: Yan Yan <evitayan@google.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

1 files changed, 8 insertions, 6 deletions

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 04d1ce9b510f..882526159d3a 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -4256,7 +4256,7 @@ static bool xfrm_migrate_selector_match(const struct xfrm_selector *sel_cmp,
 }
 
 static struct xfrm_policy *xfrm_migrate_policy_find(const struct xfrm_selector *sel,
-						    u8 dir, u8 type, struct net *net)
+						    u8 dir, u8 type, struct net *net, u32 if_id)
 {
 	struct xfrm_policy *pol, *ret = NULL;
 	struct hlist_head *chain;
@@ -4265,7 +4265,8 @@ static struct xfrm_policy *xfrm_migrate_policy_find(const struct xfrm_selector *
 	spin_lock_bh(&net->xfrm.xfrm_policy_lock);
 	chain = policy_hash_direct(net, &sel->daddr, &sel->saddr, sel->family, dir);
 	hlist_for_each_entry(pol, chain, bydst) {
-		if (xfrm_migrate_selector_match(sel, &pol->selector) &&
+		if ((if_id == 0 || pol->if_id == if_id) &&
+		    xfrm_migrate_selector_match(sel, &pol->selector) &&
 		    pol->type == type) {
 			ret = pol;
 			priority = ret->priority;
@@ -4277,7 +4278,8 @@ static struct xfrm_policy *xfrm_migrate_policy_find(const struct xfrm_selector *
 		if ((pol->priority >= priority) && ret)
 			break;
 
-		if (xfrm_migrate_selector_match(sel, &pol->selector) &&
+		if ((if_id == 0 || pol->if_id == if_id) &&
+		    xfrm_migrate_selector_match(sel, &pol->selector) &&
 		    pol->type == type) {
 			ret = pol;
 			break;
@@ -4393,7 +4395,7 @@ static int xfrm_migrate_check(const struct xfrm_migrate *m, int num_migrate)
 int xfrm_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
 		 struct xfrm_migrate *m, int num_migrate,
 		 struct xfrm_kmaddress *k, struct net *net,
-		 struct xfrm_encap_tmpl *encap)
+		 struct xfrm_encap_tmpl *encap, u32 if_id)
 {
 	int i, err, nx_cur = 0, nx_new = 0;
 	struct xfrm_policy *pol = NULL;
@@ -4412,14 +4414,14 @@ int xfrm_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
 	}
 
 	/* Stage 1 - find policy */
-	if ((pol = xfrm_migrate_policy_find(sel, dir, type, net)) == NULL) {
+	if ((pol = xfrm_migrate_policy_find(sel, dir, type, net, if_id)) == NULL) {
 		err = -ENOENT;
 		goto out;
 	}
 
 	/* Stage 2 - find and update state(s) */
 	for (i = 0, mp = m; i < num_migrate; i++, mp++) {
-		if ((x = xfrm_migrate_state_find(mp, net))) {
+		if ((x = xfrm_migrate_state_find(mp, net, if_id))) {
 			x_cur[nx_cur] = x;
 			nx_cur++;
 			xc = xfrm_state_migrate(x, mp, encap);