[SRU][J/N][PATCH 2/2] xfrm: also call xfrm_state_delete_tunnel at destroy time for states that were never added

[Tim Whisonant]

From: Sabrina Dubroca <sd at queasysnail.net>

[ Upstream commit 10deb69864840ccf96b00ac2ab3a2055c0c04721 ]

In commit b441cf3f8c4b ("xfrm: delete x->tunnel as we delete x"), I
missed the case where state creation fails between full
initialization (->init_state has been called) and being inserted on
the lists.

In this situation, ->init_state has been called, so for IPcomp
tunnels, the fallback tunnel has been created and added onto the
lists, but the user state never gets added, because we fail before
that. The user state doesn't go through __xfrm_state_delete, so we
don't call xfrm_state_delete_tunnel for those states, and we end up
leaking the FB tunnel.

There are several codepaths affected by this: the add/update paths, in
both net/key and xfrm, and the migrate code (xfrm_migrate,
xfrm_state_migrate). A "proper" rollback of the init_state work would
probably be doable in the add/update code, but for migrate it gets
more complicated as multiple states may be involved.

At some point, the new (not-inserted) state will be destroyed, so call
xfrm_state_delete_tunnel during xfrm_state_gc_destroy. Most states
will have their fallback tunnel cleaned up during __xfrm_state_delete,
which solves the issue that b441cf3f8c4b (and other patches before it)
aimed at. All states (including FB tunnels) will be removed from the
lists once xfrm_state_fini has called flush_work(&xfrm_state_gc_work).

Reported-by: syzbot+999eb23467f83f9bf9bf at syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=999eb23467f83f9bf9bf
Fixes: b441cf3f8c4b ("xfrm: delete x->tunnel as we delete x")
Signed-off-by: Sabrina Dubroca <sd at queasysnail.net>
Signed-off-by: Steffen Klassert <steffen.klassert at secunet.com>
Signed-off-by: Sasha Levin <sashal at kernel.org>
(backported from commit f7d879c19d306512c2e260f37e8a3e5c85e37c50 linux-6.12.y)
[tswhison: context adjusted due to missing commit
2a198bbec691 ("Revert "xfrm: destroy xfrm_state synchronously on net exit path"")]
CVE-2025-40256
Signed-off-by: Tim Whisonant <tim.whisonant at canonical.com>
---
 net/xfrm/xfrm_state.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 25db343b0ef60..dcd17c81794e4 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -531,6 +531,7 @@ void xfrm_state_free(struct xfrm_state *x)
 }
 EXPORT_SYMBOL(xfrm_state_free);
 
+static void xfrm_state_delete_tunnel(struct xfrm_state *x);
 static void ___xfrm_state_destroy(struct xfrm_state *x)
 {
 	hrtimer_cancel(&x->mtimer);
@@ -545,6 +546,7 @@ static void ___xfrm_state_destroy(struct xfrm_state *x)
 	kfree(x->preplay_esn);
 	if (x->type_offload)
 		xfrm_put_type_offload(x->type_offload);
+	xfrm_state_delete_tunnel(x);
 	if (x->type) {
 		x->type->destructor(x);
 		xfrm_put_type(x->type);
@@ -748,7 +750,6 @@ void __xfrm_state_destroy(struct xfrm_state *x, bool sync)
 }
 EXPORT_SYMBOL(__xfrm_state_destroy);
 
-static void xfrm_state_delete_tunnel(struct xfrm_state *x);
 int __xfrm_state_delete(struct xfrm_state *x)
 {
 	struct net *net = xs_net(x);
-- 
2.43.0