Commit 7081d46d authored by Keenan Dong's avatar Keenan Dong Committed by Steffen Klassert
Browse files

xfrm: account XFRMA_IF_ID in aevent size calculation 



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: 7e652640 ("xfrm: Add a new lookup key to match xfrm interfaces.")
Reported-by: default avatarKeenan Dong <keenanat2000@gmail.com>
Signed-off-by: default avatarKeenan Dong <keenanat2000@gmail.com>
Signed-off-by: default avatarSteffen Klassert <steffen.klassert@secunet.com>
parent 71a98248

net/xfrm/xfrm_user.c

+8 −2
Original line number Diff line number Diff line
@@ -2677,7 +2677,8 @@ 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)
@@ -2789,7 +2790,12 @@ 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(xfrm_net_nlsk(net, skb), r_skb, NETLINK_CB(skb).portid);

	spin_unlock_bh(&x->lock);