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Subject[PATCH net 3/3] ethtool: reject unrecognized request flags
Date
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
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