[PATCH 6.18 061/198] xfrm: account XFRMA_IF_ID in aevent size calculation

Greg Kroah-Hartman
2026-04-20T15:58:41Z

From: Keenan Dong <keenanat2000@gmail.com>

[ Upstream commit 7081d46d32312f1a31f0e0e99c6835a394037599 ]

xfrm_get_ae() allocates the reply skb with xfrm_aevent_msgsize(), then
build_aevent() appends attributes including XFRMA_IF_ID when x->if_id is
set.

xfrm_aevent_msgsize() does not include space for XFRMA_IF_ID. For states
with if_id, build_aevent() can fail with -EMSGSIZE and hit BUG_ON(err < 0)
in xfrm_get_ae(), turning a malformed netlink interaction into a kernel
panic.

Account XFRMA_IF_ID in the size calculation unconditionally and replace
the BUG_ON with normal error unwinding.

Fixes: 7e6526404ade ("xfrm: Add a new lookup key to match xfrm interfaces.")
Reported-by: Keenan Dong <keenanat2000@gmail.com>
Signed-off-by: Keenan Dong <keenanat2000@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/xfrm/xfrm_user.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index 306e4f65ce264..1ddcf2a1eff7a 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -2668,7 +2668,8 @@ static inline unsigned int xfrm_aevent_msgsize(struct xfrm_state *x)
+ nla_total_size(4) /* XFRM_AE_RTHR */
+ nla_total_size(4) /* XFRM_AE_ETHR */
+ nla_total_size(sizeof(x->dir)) /* XFRMA_SA_DIR */
- + nla_total_size(4); /* XFRMA_SA_PCPU */
+ + nla_total_size(4) /* XFRMA_SA_PCPU */
+ + nla_total_size(sizeof(x->if_id)); /* XFRMA_IF_ID */
}

static int build_aevent(struct sk_buff *skb, struct xfrm_state *x, const struct km_event *c)
@@ -2780,7 +2781,12 @@ static int xfrm_get_ae(struct sk_buff *skb, struct nlmsghdr *nlh,
c.portid = nlh->nlmsg_pid;

err = build_aevent(r_skb, x, &c);
- BUG_ON(err < 0);
+ if (err < 0) {
+ spin_unlock_bh(&x->lock);
+ xfrm_state_put(x);
+ kfree_skb(r_skb);
+ return err;
+ }

err = nlmsg_unicast(net->xfrm.nlsk, r_skb, NETLINK_CB(skb).portid);
spin_unlock_bh(&x->lock);
--
2.53.0