netlink: introduce NLA_POLICY_MAX_BE

netlink allows to specify allowed ranges for integer types.
Unfortunately, nfnetlink passes integers in big endian, so the existing
NLA_POLICY_MAX() cannot be used.

At the moment, nfnetlink users, such as nf_tables, need to resort to
programmatic checking via helpers such as nft_parse_u32_check().

This is both cumbersome and error prone.  This adds NLA_POLICY_MAX_BE
which adds range check support for BE16, BE32 and BE64 integers.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 27 insertions, 4 deletions

diff --git a/lib/nlattr.c b/lib/nlattr.c
index 86029ad5ead4..40f22b177d69 100644
--- a/lib/nlattr.c
+++ b/lib/nlattr.c
@@ -159,6 +159,31 @@ void nla_get_range_unsigned(const struct nla_policy *pt,
 	}
 }
 
+static u64 nla_get_attr_bo(const struct nla_policy *pt,
+			   const struct nlattr *nla)
+{
+	switch (pt->type) {
+	case NLA_U16:
+		if (pt->network_byte_order)
+			return ntohs(nla_get_be16(nla));
+
+		return nla_get_u16(nla);
+	case NLA_U32:
+		if (pt->network_byte_order)
+			return ntohl(nla_get_be32(nla));
+
+		return nla_get_u32(nla);
+	case NLA_U64:
+		if (pt->network_byte_order)
+			return be64_to_cpu(nla_get_be64(nla));
+
+		return nla_get_u64(nla);
+	}
+
+	WARN_ON_ONCE(1);
+	return 0;
+}
+
 static int nla_validate_range_unsigned(const struct nla_policy *pt,
 				       const struct nlattr *nla,
 				       struct netlink_ext_ack *extack,
@@ -172,12 +197,10 @@ static int nla_validate_range_unsigned(const struct nla_policy *pt,
 		value = nla_get_u8(nla);
 		break;
 	case NLA_U16:
-		value = nla_get_u16(nla);
-		break;
 	case NLA_U32:
-		value = nla_get_u32(nla);
-		break;
 	case NLA_U64:
+		value = nla_get_attr_bo(pt, nla);
+		break;
 	case NLA_MSECS:
 		value = nla_get_u64(nla);
 		break;