xfrm: provide message size for XFRM_MSG_MAPPING

The compat 64=>32 translation path handles XFRM_MSG_MAPPING, but
xfrm_msg_min[] does not provide the native payload size for this
message type.

Add the missing XFRM_MSG_MAPPING entry so compat translation can size
and translate mapping notifications correctly.

Fixes: 5461fc0 ("xfrm/compat: Add 64=>32-bit messages translator")
Cc: stable@kernel.org
Reported-by: Yuan Tan <yuantan098@gmail.com>
Reported-by: Yifan Wu <yifanwucs@gmail.com>
Reported-by: Juefei Pu <tomapufckgml@gmail.com>
Reported-by: Xin Liu <bird@lzu.edu.cn>
Signed-off-by: Ruijie Li <ruijieli51@gmail.com>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

Author: ruijieli51

net/xfrm/xfrm_user.c

@@ -3323,6 +3323,7 @@ const int xfrm_msg_min[XFRM_NR_MSGTYPES] = {
 	[XFRM_MSG_GETSADINFO  - XFRM_MSG_BASE] = sizeof(u32),
 	[XFRM_MSG_NEWSPDINFO  - XFRM_MSG_BASE] = sizeof(u32),
 	[XFRM_MSG_GETSPDINFO  - XFRM_MSG_BASE] = sizeof(u32),
+	[XFRM_MSG_MAPPING     - XFRM_MSG_BASE] = XMSGSIZE(xfrm_user_mapping),
 	[XFRM_MSG_SETDEFAULT  - XFRM_MSG_BASE] = XMSGSIZE(xfrm_userpolicy_default),
 	[XFRM_MSG_GETDEFAULT  - XFRM_MSG_BASE] = XMSGSIZE(xfrm_userpolicy_default),
 };