Subject: [PATCH net-next 6/6] ethtool: specify which header flags are supported per command

From: Jakub Kicinski <[email-masked]>
Date: Mon, 5 Oct 2020 08:57:53 -0700

Perform header flags validation through the policy.

Only pause command supports ETHTOOL_FLAG_STATS. Create a separate
policy to be able to express that in policy dumps to user space.

Note that even though the core will validate the header policy,
it cannot record multiple layers of attributes and we have to
re-parse header sub-attrs. When doing so we could skip attribute
validation, or use most permissive policy.

Signed-off-by: Jakub Kicinski <[email-masked]>
---
 net/ethtool/netlink.c | 31 +++++++++++++++++++++----------
 net/ethtool/netlink.h |  1 +
 net/ethtool/pause.c   |  2 +-
 3 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index e78ff7ce2a7d..b972789d6b8d 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -9,12 +9,26 @@ static struct genl_family ethtool_genl_family;
 static bool ethnl_ok __read_mostly;
 static u32 ethnl_bcast_seq;
 
+#define ETHTOOL_FLAGS_BASIC (ETHTOOL_FLAG_COMPACT_BITSETS |	\
+			     ETHTOOL_FLAG_OMIT_REPLY)
+#define ETHTOOL_FLAGS_STATS (ETHTOOL_FLAGS_BASIC | ETHTOOL_FLAG_STATS)
+
 const struct nla_policy ethnl_header_policy[ETHTOOL_A_HEADER_MAX + 1] = {
 	[ETHTOOL_A_HEADER_UNSPEC]	= { .type = NLA_REJECT },
 	[ETHTOOL_A_HEADER_DEV_INDEX]	= { .type = NLA_U32 },
 	[ETHTOOL_A_HEADER_DEV_NAME]	= { .type = NLA_NUL_STRING,
 					    .len = ALTIFNAMSIZ - 1 },
-	[ETHTOOL_A_HEADER_FLAGS]	= { .type = NLA_U32 },
+	[ETHTOOL_A_HEADER_FLAGS]	= NLA_POLICY_MASK(NLA_U32,
+							  ETHTOOL_FLAGS_BASIC),
+};
+
+const struct nla_policy ethnl_header_policy_stats[ETHTOOL_A_HEADER_MAX + 1] = {
+	[ETHTOOL_A_HEADER_UNSPEC]	= { .type = NLA_REJECT },
+	[ETHTOOL_A_HEADER_DEV_INDEX]	= { .type = NLA_U32 },
+	[ETHTOOL_A_HEADER_DEV_NAME]	= { .type = NLA_NUL_STRING,
+					    .len = ALTIFNAMSIZ - 1 },
+	[ETHTOOL_A_HEADER_FLAGS]	= NLA_POLICY_MASK(NLA_U32,
+							  ETHTOOL_FLAGS_STATS),
 };
 
 /**
@@ -47,19 +61,16 @@ int ethnl_parse_header_dev_get(struct ethnl_req_info *req_info,
 		NL_SET_ERR_MSG(extack, "request header missing");
 		return -EINVAL;
 	}
+	/* Use most permissive header policy here, ops should specify their
+	 * actual header policy via NLA_POLICY_NESTED(), and the real
+	 * validation will happen in genetlink code.
+	 */
 	ret = nla_parse_nested(tb, ETHTOOL_A_HEADER_MAX, header,
-			       ethnl_header_policy, extack);
+			       ethnl_header_policy_stats, extack);
 	if (ret < 0)
 		return ret;
-	if (tb[ETHTOOL_A_HEADER_FLAGS]) {
+	if (tb[ETHTOOL_A_HEADER_FLAGS])
 		flags = nla_get_u32(tb[ETHTOOL_A_HEADER_FLAGS]);
-		if (flags & ~ETHTOOL_FLAG_ALL) {
-			NL_SET_ERR_MSG_ATTR(extack, tb[ETHTOOL_A_HEADER_FLAGS],
-					    "unrecognized request flags");
-			nl_set_extack_cookie_u32(extack, ETHTOOL_FLAG_ALL);
-			return -EOPNOTSUPP;
-		}
-	}
 
 	devname_attr = tb[ETHTOOL_A_HEADER_DEV_NAME];
 	if (tb[ETHTOOL_A_HEADER_DEV_INDEX]) {
diff --git a/net/ethtool/netlink.h b/net/ethtool/netlink.h
index 4fcd2e8b259b..f04d94e5fa77 100644
--- a/net/ethtool/netlink.h
+++ b/net/ethtool/netlink.h
@@ -348,6 +348,7 @@ extern const struct ethnl_request_ops ethnl_eee_request_ops;
 extern const struct ethnl_request_ops ethnl_tsinfo_request_ops;
 
 extern const struct nla_policy ethnl_header_policy[ETHTOOL_A_HEADER_MAX + 1];
+extern const struct nla_policy ethnl_header_policy_stats[ETHTOOL_A_HEADER_MAX + 1];
 extern const struct nla_policy ethnl_strset_get_policy[ETHTOOL_A_STRSET_MAX + 1];
 extern const struct nla_policy ethnl_linkinfo_get_policy[ETHTOOL_A_LINKINFO_MAX + 1];
 extern const struct nla_policy ethnl_linkinfo_set_policy[ETHTOOL_A_LINKINFO_MAX + 1];
diff --git a/net/ethtool/pause.c b/net/ethtool/pause.c
index a7fbe0e4dca6..a5c2abddc992 100644
--- a/net/ethtool/pause.c
+++ b/net/ethtool/pause.c
@@ -19,7 +19,7 @@ struct pause_reply_data {
 const struct nla_policy ethnl_pause_get_policy[ETHTOOL_A_PAUSE_MAX + 1] = {
 	[ETHTOOL_A_PAUSE_UNSPEC]		= { .type = NLA_REJECT },
 	[ETHTOOL_A_PAUSE_HEADER]		=
-		NLA_POLICY_NESTED(ethnl_header_policy),
+		NLA_POLICY_NESTED(ethnl_header_policy_stats),
 	[ETHTOOL_A_PAUSE_AUTONEG]		= { .type = NLA_REJECT },
 	[ETHTOOL_A_PAUSE_RX]			= { .type = NLA_REJECT },
 	[ETHTOOL_A_PAUSE_TX]			= { .type = NLA_REJECT },
-- 
2.26.2