[PATCH net 06/10] ethtool: tsinfo: fix uninitialized stats on the by-PHC path

[Jakub Kicinski <kuba@kernel.org>]

tsinfo_prepare_data() has two code paths: a "by-PHC" path for
user-specified hardware timestamping providers, and the old path.
Commit 89e281ebff72 ("ethtool: init tsinfo stats if requested") added
ethtool_stats_init() to mark stat slots as ETHTOOL_STAT_NOT_SET before
the driver callback populates them, but placed the call inside the
old-path block.

When commit b9e3f7dc9ed9 ("net: ethtool: tsinfo: Enhance tsinfo to
support several hwtstamp by net topology") added the by-PHC early
return, it landed above the stats initialization. On that path
the stats array retains the zero-fill from ethnl_init_reply_data()'s
zalloc. This leads to the reply including a stats nest with four
zero-valued attributes that should have been absent.

Reject GET requests for stats with HWTSTAMP_PROVIDER or dump.

Fixes: b9e3f7dc9ed9 ("net: ethtool: tsinfo: Enhance tsinfo to support several hwtstamp by net topology")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
CC: andrew@lunn.ch
CC: maxime.chevallier@bootlin.com
CC: kory.maincent@bootlin.com
CC: kees@kernel.org
---
 net/ethtool/tsinfo.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/net/ethtool/tsinfo.c b/net/ethtool/tsinfo.c
index a865f0fdd26b..f54fe6b662b2 100644
--- a/net/ethtool/tsinfo.c
+++ b/net/ethtool/tsinfo.c
@@ -83,6 +83,11 @@ tsinfo_parse_request(struct ethnl_req_info *req_base,
 	if (!tb[ETHTOOL_A_TSINFO_HWTSTAMP_PROVIDER])
 		return 0;
 
+	if (req_base->flags & ETHTOOL_FLAG_STATS) {
+		NL_SET_ERR_MSG(extack, "can't query statistics for a provider");
+		return -EOPNOTSUPP;
+	}
+
 	return ts_parse_hwtst_provider(tb[ETHTOOL_A_TSINFO_HWTSTAMP_PROVIDER],
 				       &req->hwprov_desc, extack, &mod);
 }
@@ -523,6 +528,12 @@ int ethnl_tsinfo_start(struct netlink_callback *cb)
 	if (ret < 0)
 		goto free_reply_data;
 
+	if (req_info->base.flags & ETHTOOL_FLAG_STATS) {
+		NL_SET_ERR_MSG(cb->extack, "stats not supported in dump");
+		ret = -EOPNOTSUPP;
+		goto err_dev_put;
+	}
+
 	ctx->req_info = req_info;
 	ctx->reply_data = reply_data;
 	ctx->pos_ifindex = 0;
@@ -532,6 +543,8 @@ int ethnl_tsinfo_start(struct netlink_callback *cb)
 
 	return 0;
 
+err_dev_put:
+	ethnl_parse_header_dev_put(&req_info->base);
 free_reply_data:
 	kfree(reply_data);
 free_req_info:
-- 
2.54.0