netdev - [PATCH ipsec] xfrm: Don't allow optional intermediate templates that changes the address family

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Date:   Fri, 31 Mar 2023 08:21:40 +0200
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     <netdev@...r.kernel.org>, <devel@...ux-ipsec.org>
CC:     Hyunwoo Kim <v4bel@...ori.io>,
        Tudor Ambarus <tudordana@...gle.com>,
        "Eric Dumazet" <edumazet@...gle.com>
Subject: [PATCH ipsec] xfrm: Don't allow optional intermediate templates that
 changes the address family

When an optional intermediate template changes the address family,
it is unclear which family the next template should have. This can
lead to misinterpretations of IPv4/IPv6 addresses. So reject
optional intermediate templates on insertion time.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Hyunwoo Kim <v4bel@...ori.io>
Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
---
 net/xfrm/xfrm_user.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index 103af2b3e986..df4e840b630e 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1770,6 +1770,7 @@ static void copy_templates(struct xfrm_policy *xp, struct xfrm_user_tmpl *ut,
 static int validate_tmpl(int nr, struct xfrm_user_tmpl *ut, u16 family,
 			 struct netlink_ext_ack *extack)
 {
+	bool opt_family_change;
 	u16 prev_family;
 	int i;
 
@@ -1778,6 +1779,7 @@ static int validate_tmpl(int nr, struct xfrm_user_tmpl *ut, u16 family,
 		return -EINVAL;
 	}
 
+	opt_family_change = false;
 	prev_family = family;
 
 	for (i = 0; i < nr; i++) {
@@ -1791,9 +1793,16 @@ static int validate_tmpl(int nr, struct xfrm_user_tmpl *ut, u16 family,
 		if (!ut[i].family)
 			ut[i].family = family;
 
+		if (opt_family_change) {
+			NL_SET_ERR_MSG(extack, "Optional intermediate templates don't support family changes");
+			return -EINVAL;
+		}
+
 		switch (ut[i].mode) {
 		case XFRM_MODE_TUNNEL:
 		case XFRM_MODE_BEET:
+			if (ut[i].optional && ut[i].family != prev_family)
+				opt_family_change = true;
 			break;
 		default:
 			if (ut[i].family != prev_family) {
-- 
2.34.1