Merge branch 'ethtool-fail-with-error-if-request-has-unknown-flags'

Michal Kubecek says:

====================
ethtool: fail with error if request has unknown flags

Jakub Kicinski pointed out that if unrecognized flags are set in netlink
header request, kernel shoud fail with an error rather than silently
ignore them so that we have more freedom in future flags semantics.

To help userspace with handling such errors, inform the client which
flags are supported by kernel. For that purpose, we need to allow
passing cookies as part of extack also in case of error (they can be
only passed on success now).
====================

Signed-off-by: David S. Miller <[email protected]>

3 files changed, 38 insertions, 30 deletions

diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index 205fa7b1f07a..4090524c3462 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -119,6 +119,15 @@ static inline void nl_set_extack_cookie_u64(struct netlink_ext_ack *extack,
 	extack->cookie_len = sizeof(__cookie);
 }
 
+static inline void nl_set_extack_cookie_u32(struct netlink_ext_ack *extack,
+					    u32 cookie)
+{
+	u32 __cookie = cookie;
+
+	memcpy(extack->cookie, &__cookie, sizeof(__cookie));
+	extack->cookie_len = sizeof(__cookie);
+}
+
 void netlink_kernel_release(struct sock *sk);
 int __netlink_change_ngroups(struct sock *sk, unsigned int groups);
 int netlink_change_ngroups(struct sock *sk, unsigned int groups);
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;
 }
 
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 5313f1cec170..2f234791b879 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2392,19 +2392,14 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
 	if (nlk_has_extack && extack && extack->_msg)
 		tlvlen += nla_total_size(strlen(extack->_msg) + 1);
 
-	if (err) {
-		if (!(nlk->flags & NETLINK_F_CAP_ACK))
-			payload += nlmsg_len(nlh);
-		else
-			flags |= NLM_F_CAPPED;
-		if (nlk_has_extack && extack && extack->bad_attr)
-			tlvlen += nla_total_size(sizeof(u32));
-	} else {
+	if (err && !(nlk->flags & NETLINK_F_CAP_ACK))
+		payload += nlmsg_len(nlh);
+	else
 		flags |= NLM_F_CAPPED;
-
-		if (nlk_has_extack && extack && extack->cookie_len)
-			tlvlen += nla_total_size(extack->cookie_len);
-	}
+	if (err && nlk_has_extack && extack && extack->bad_attr)
+		tlvlen += nla_total_size(sizeof(u32));
+	if (nlk_has_extack && extack && extack->cookie_len)
+		tlvlen += nla_total_size(extack->cookie_len);
 
 	if (tlvlen)
 		flags |= NLM_F_ACK_TLVS;
@@ -2427,20 +2422,16 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
 			WARN_ON(nla_put_string(skb, NLMSGERR_ATTR_MSG,
 					       extack->_msg));
 		}
-		if (err) {
-			if (extack->bad_attr &&
-			    !WARN_ON((u8 *)extack->bad_attr < in_skb->data ||
-				     (u8 *)extack->bad_attr >= in_skb->data +
-							       in_skb->len))
-				WARN_ON(nla_put_u32(skb, NLMSGERR_ATTR_OFFS,
-						    (u8 *)extack->bad_attr -
-						    (u8 *)nlh));
-		} else {
-			if (extack->cookie_len)
-				WARN_ON(nla_put(skb, NLMSGERR_ATTR_COOKIE,
-						extack->cookie_len,
-						extack->cookie));
-		}
+		if (err && extack->bad_attr &&
+		    !WARN_ON((u8 *)extack->bad_attr < in_skb->data ||
+			     (u8 *)extack->bad_attr >= in_skb->data +
+						       in_skb->len))
+			WARN_ON(nla_put_u32(skb, NLMSGERR_ATTR_OFFS,
+					    (u8 *)extack->bad_attr -
+					    (u8 *)nlh));
+		if (extack->cookie_len)
+			WARN_ON(nla_put(skb, NLMSGERR_ATTR_COOKIE,
+					extack->cookie_len, extack->cookie));
 	}
 
 	nlmsg_end(skb, rep);