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Message-Id: <40d6e189e3661dc996f7646c848bfb067ac324cb.1584292182.git.mkubecek@suse.cz>
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From:   Michal Kubecek <mkubecek@suse.cz>
Subject: [PATCH net 3/3] ethtool: reject unrecognized request flags
To:     David Miller <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>, netdev@vger.kernel.org
Cc:     Johannes Berg <johannes@sipsolutions.net>,
        linux-kernel@vger.kernel.org
Date:   Sun, 15 Mar 2020 18:17:53 +0100 (CET)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

As pointed out by Jakub Kicinski, we ethtool netlink code should respond
with an error if request head has flags set which are not recognized by
kernel, either as a mistake or because it expects functionality introduced
in later kernel versions.

To avoid unnecessary roundtrips, use extack cookie to  provide the
information about supported request flags.

Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
---
 net/ethtool/netlink.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index 180c194fab07..fc9e0b806889 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -40,6 +40,7 @@ int ethnl_parse_header(struct ethnl_req_info *req_info,
 	struct nlattr *tb[ETHTOOL_A_HEADER_MAX + 1];
 	const struct nlattr *devname_attr;
 	struct net_device *dev = NULL;
+	u32 flags = 0;
 	int ret;
 
 	if (!header) {
@@ -50,8 +51,17 @@ int ethnl_parse_header(struct ethnl_req_info *req_info,
 			       ethnl_header_policy, extack);
 	if (ret < 0)
 		return ret;
-	devname_attr = tb[ETHTOOL_A_HEADER_DEV_NAME];
+	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]) {
 		u32 ifindex = nla_get_u32(tb[ETHTOOL_A_HEADER_DEV_INDEX]);
 
@@ -90,9 +100,7 @@ int ethnl_parse_header(struct ethnl_req_info *req_info,
 	}
 
 	req_info->dev = dev;
-	if (tb[ETHTOOL_A_HEADER_FLAGS])
-		req_info->flags = nla_get_u32(tb[ETHTOOL_A_HEADER_FLAGS]);
-
+	req_info->flags = flags;
 	return 0;
 }
 
-- 
2.25.1