net/sched: cls_flower: add policy for TCA_FLOWER_KEY_FLAGS

This policy guards fl_set_key_flags() from seeing flags
not used in the context of TCA_FLOWER_KEY_FLAGS.

In order For the policy check to be performed with the
correct endianness, then we also needs to change the
attribute type to NLA_BE32 (Thanks Davide).

TCA_FLOWER_KEY_FLAGS{,_MASK} already has a be32 comment
in include/uapi/linux/pkt_cls.h.

Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Tested-by: Davide Caratti <dcaratti@redhat.com>
Reviewed-by: Davide Caratti <dcaratti@redhat.com>
Link: https://patch.msgid.link/20240713021911.1631517-6-ast@fiberby.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Asbjørn Sloth Tønnesen

net/sched/cls_flower.c

@@ -41,6 +41,10 @@
 #define TCA_FLOWER_KEY_CT_FLAGS_MASK \
 		(TCA_FLOWER_KEY_CT_FLAGS_MAX - 1)
 
+#define TCA_FLOWER_KEY_FLAGS_POLICY_MASK \
+		(TCA_FLOWER_KEY_FLAGS_IS_FRAGMENT | \
+		TCA_FLOWER_KEY_FLAGS_FRAG_IS_FIRST)
+
 #define TUNNEL_FLAGS_PRESENT (\
 	_BITUL(IP_TUNNEL_CSUM_BIT) |		\
 	_BITUL(IP_TUNNEL_DONT_FRAGMENT_BIT) |	\
@@ -676,8 +680,10 @@ static const struct nla_policy fl_policy[TCA_FLOWER_MAX + 1] = {
 	[TCA_FLOWER_KEY_ENC_UDP_SRC_PORT_MASK]	= { .type = NLA_U16 },
 	[TCA_FLOWER_KEY_ENC_UDP_DST_PORT]	= { .type = NLA_U16 },
 	[TCA_FLOWER_KEY_ENC_UDP_DST_PORT_MASK]	= { .type = NLA_U16 },
-	[TCA_FLOWER_KEY_FLAGS]		= { .type = NLA_U32 },
-	[TCA_FLOWER_KEY_FLAGS_MASK]	= { .type = NLA_U32 },
+	[TCA_FLOWER_KEY_FLAGS]		= NLA_POLICY_MASK(NLA_BE32,
+							  TCA_FLOWER_KEY_FLAGS_POLICY_MASK),
+	[TCA_FLOWER_KEY_FLAGS_MASK]	= NLA_POLICY_MASK(NLA_BE32,
+							  TCA_FLOWER_KEY_FLAGS_POLICY_MASK),
 	[TCA_FLOWER_KEY_ICMPV4_TYPE]	= { .type = NLA_U8 },
 	[TCA_FLOWER_KEY_ICMPV4_TYPE_MASK] = { .type = NLA_U8 },
 	[TCA_FLOWER_KEY_ICMPV4_CODE]	= { .type = NLA_U8 },