[PATCH 18/18] xfrm: Enable compat syscalls

[Dmitry Safonov]

Compatible syscalls were disabled for xfrm with the following commits:
19d7df69fdb2 ("xfrm: Refuse to insert 32 bit userspace socket policies
on 64 bit systems") and 74005991b78a ("xfrm: Do not parse 32bits
compiled xfrm netlink msg on 64bits host").

As some structures in xfrm uapi header were not packed by a mistake,
they differ in size between 64-bit and 32-bit applications:

          32-bit UABI                 |             64-bit UABI
--------------------------------------|--------------------------------------
sizeof(xfrm_usersa_info)     = 220    |    sizeof(xfrm_usersa_info)     = 224
sizeof(xfrm_userpolicy_info) = 164    |    sizeof(xfrm_userpolicy_info) = 168
sizeof(xfrm_userspi_info)    = 228    |    sizeof(xfrm_userspi_info)    = 232
sizeof(xfrm_user_acquire)    = 276    |    sizeof(xfrm_user_acquire)    = 280
sizeof(xfrm_user_expire)     = 224    |    sizeof(xfrm_user_expire)     = 232
sizeof(xfrm_user_polexpire)  = 168    |    sizeof(xfrm_user_polexpire)  = 176

With previous patches compatible layer was added to xfrm, so now we
support users of both ABI. A selftest to check work of ipsec tunnel is
present in net/ipsec. It can be easily compiled as compat application
and doesn't require any compat libraries.

Revert the mentioned commits and check the size of received message
according to native/compat syscall.

Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Fan Du <fan.du@xxxxxxxxx>
Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Cc: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
Cc: netdev@xxxxxxxxxxxxxxx
Signed-off-by: Dmitry Safonov <dima@xxxxxxxxxx>
---
 net/xfrm/xfrm_state.c |  3 ---
 net/xfrm/xfrm_user.c  | 35 ++++++++++++++++++++++++++++++-----
 2 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 3f48a6925606..515a565bfc37 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -2057,9 +2057,6 @@ int xfrm_user_policy(struct sock *sk, int optname, u8 __user *optval, int optlen
 	struct xfrm_mgr *km;
 	struct xfrm_policy *pol = NULL;
 
-	if (in_compat_syscall())
-		return -EOPNOTSUPP;
-
 	if (!optval && !optlen) {
 		xfrm_sk_policy_insert(sk, XFRM_POLICY_IN, NULL);
 		xfrm_sk_policy_insert(sk, XFRM_POLICY_OUT, NULL);
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index 7e3a132b76fb..f6da6ea65d37 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -2634,6 +2634,30 @@ static const int xfrm_msg_min[XFRM_NR_MSGTYPES] = {
 	[XFRM_MSG_GETSPDINFO  - XFRM_MSG_BASE] = sizeof(u32),
 };
 
+static const int xfrm_msg_min_compat[XFRM_NR_MSGTYPES] = {
+	[XFRM_MSG_NEWSA       - XFRM_MSG_BASE] = XMSGSIZE(xfrm_usersa_info_packed),
+	[XFRM_MSG_DELSA       - XFRM_MSG_BASE] = XMSGSIZE(xfrm_usersa_id),
+	[XFRM_MSG_GETSA       - XFRM_MSG_BASE] = XMSGSIZE(xfrm_usersa_id),
+	[XFRM_MSG_NEWPOLICY   - XFRM_MSG_BASE] = XMSGSIZE(xfrm_userpolicy_info_packed),
+	[XFRM_MSG_DELPOLICY   - XFRM_MSG_BASE] = XMSGSIZE(xfrm_userpolicy_id),
+	[XFRM_MSG_GETPOLICY   - XFRM_MSG_BASE] = XMSGSIZE(xfrm_userpolicy_id),
+	[XFRM_MSG_ALLOCSPI    - XFRM_MSG_BASE] = XMSGSIZE(xfrm_userspi_info_packed),
+	[XFRM_MSG_ACQUIRE     - XFRM_MSG_BASE] = XMSGSIZE(xfrm_user_acquire_packed),
+	[XFRM_MSG_EXPIRE      - XFRM_MSG_BASE] = XMSGSIZE(xfrm_user_expire_packed),
+	[XFRM_MSG_UPDPOLICY   - XFRM_MSG_BASE] = XMSGSIZE(xfrm_userpolicy_info_packed),
+	[XFRM_MSG_UPDSA       - XFRM_MSG_BASE] = XMSGSIZE(xfrm_usersa_info_packed),
+	[XFRM_MSG_POLEXPIRE   - XFRM_MSG_BASE] = XMSGSIZE(xfrm_user_polexpire_packed),
+	[XFRM_MSG_FLUSHSA     - XFRM_MSG_BASE] = XMSGSIZE(xfrm_usersa_flush),
+	[XFRM_MSG_FLUSHPOLICY - XFRM_MSG_BASE] = 0,
+	[XFRM_MSG_NEWAE       - XFRM_MSG_BASE] = XMSGSIZE(xfrm_aevent_id),
+	[XFRM_MSG_GETAE       - XFRM_MSG_BASE] = XMSGSIZE(xfrm_aevent_id),
+	[XFRM_MSG_REPORT      - XFRM_MSG_BASE] = XMSGSIZE(xfrm_user_report),
+	[XFRM_MSG_MIGRATE     - XFRM_MSG_BASE] = XMSGSIZE(xfrm_userpolicy_id),
+	[XFRM_MSG_GETSADINFO  - XFRM_MSG_BASE] = sizeof(u32),
+	[XFRM_MSG_NEWSPDINFO  - XFRM_MSG_BASE] = sizeof(u32),
+	[XFRM_MSG_GETSPDINFO  - XFRM_MSG_BASE] = sizeof(u32),
+};
+
 #undef XMSGSIZE
 
 static const struct nla_policy xfrma_policy[XFRMA_MAX+1] = {
@@ -2715,10 +2739,7 @@ static int xfrm_user_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
 	struct net *net = sock_net(skb->sk);
 	struct nlattr *attrs[XFRMA_MAX+1];
 	const struct xfrm_link *link;
-	int type, err;
-
-	if (in_compat_syscall())
-		return -EOPNOTSUPP;
+	int type, err, hdrlen;
 
 	type = nlh->nlmsg_type;
 	if (type > XFRM_MSG_MAX)
@@ -2747,7 +2768,11 @@ static int xfrm_user_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
 		}
 	}
 
-	err = nlmsg_parse(nlh, xfrm_msg_min[type], attrs,
+	hdrlen = xfrm_msg_min[type];
+	if (in_compat_syscall())
+		hdrlen = xfrm_msg_min_compat[type];
+
+	err = nlmsg_parse(nlh, hdrlen, attrs,
 			  link->nla_max ? : XFRMA_MAX,
 			  link->nla_pol ? : xfrma_policy, extack);
 	if (err < 0)
-- 
2.13.6