[PATCH net 1/2] net: ethtool: netlink: Allow NULL nlattrs when getting a phy_device

Maxime Chevallier
2025-02-27T18:25:00Z

ethnl_req_get_phydev() is used to lookup a phy_device, in the case an
ethtool netlink command targets a specific phydev within a netdev's
topology.

It takes as a parameter a const struct nlattr *header that's used for
error handling :

if (!phydev) {
NL_SET_ERR_MSG_ATTR(extack, header,
"no phy matching phyindex");
return ERR_PTR(-ENODEV);
}

In the notify path after a ->set operation however, there's no request
attributes available.

The typical callsite for the above function looks like:

phydev = ethnl_req_get_phydev(req_base, tb[ETHTOOL_A_XXX_HEADER],
info->extack);

So, when tb is NULL (such as in the ethnl notify path), we have a nice
crash.

It turns out that there's only the PLCA command that is in that case, as
the other phydev-specific commands don't have a notification.

This commit fixes the crash by passing the cmd index and the nlattr
array separately, allowing NULL-checking it directly inside the helper.

Fixes: c15e065b46dc ("net: ethtool: Allow passing a phy index for some commands")
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---

I didn't include a Reported-by tag as the report was done outside of the
mailing list, and checkpatch wants a "Closes:" if I add Reported-by...

net/ethtool/cabletest.c | 8 ++++----
net/ethtool/linkstate.c | 2 +-
net/ethtool/netlink.c | 6 +++---
net/ethtool/netlink.h | 5 +++--
net/ethtool/phy.c | 2 +-
net/ethtool/plca.c | 6 +++---
net/ethtool/pse-pd.c | 4 ++--
net/ethtool/stats.c | 2 +-
net/ethtool/strset.c | 2 +-
9 files changed, 19 insertions(+), 18 deletions(-)

diff --git a/net/ethtool/cabletest.c b/net/ethtool/cabletest.c
index f22051f33868..84096f6b0236 100644
--- a/net/ethtool/cabletest.c
+++ b/net/ethtool/cabletest.c
@@ -72,8 +72,8 @@ int ethnl_act_cable_test(struct sk_buff *skb, struct genl_info *info)
dev = req_info.dev;

rtnl_lock();
- phydev = ethnl_req_get_phydev(&req_info,
- tb[ETHTOOL_A_CABLE_TEST_HEADER],
+ phydev = ethnl_req_get_phydev(&req_info, tb,
+ ETHTOOL_A_CABLE_TEST_HEADER,
info->extack);
if (IS_ERR_OR_NULL(phydev)) {
ret = -EOPNOTSUPP;
@@ -339,8 +339,8 @@ int ethnl_act_cable_test_tdr(struct sk_buff *skb, struct genl_info *info)
goto out_dev_put;

rtnl_lock();
- phydev = ethnl_req_get_phydev(&req_info,
- tb[ETHTOOL_A_CABLE_TEST_TDR_HEADER],
+ phydev = ethnl_req_get_phydev(&req_info, tb,
+ ETHTOOL_A_CABLE_TEST_TDR_HEADER,
info->extack);
if (IS_ERR_OR_NULL(phydev)) {
ret = -EOPNOTSUPP;
diff --git a/net/ethtool/linkstate.c b/net/ethtool/linkstate.c
index af19e1bed303..05a5f72c99fa 100644
--- a/net/ethtool/linkstate.c
+++ b/net/ethtool/linkstate.c
@@ -103,7 +103,7 @@ static int linkstate_prepare_data(const struct ethnl_req_info *req_base,
struct phy_device *phydev;
int ret;

- phydev = ethnl_req_get_phydev(req_base, tb[ETHTOOL_A_LINKSTATE_HEADER],
+ phydev = ethnl_req_get_phydev(req_base, tb, ETHTOOL_A_LINKSTATE_HEADER,
info->extack);
if (IS_ERR(phydev)) {
ret = PTR_ERR(phydev);
diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index b4c45207fa32..734849a57369 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -211,7 +211,7 @@ int ethnl_parse_header_dev_get(struct ethnl_req_info *req_info,
}

struct phy_device *ethnl_req_get_phydev(const struct ethnl_req_info *req_info,
- const struct nlattr *header,
+ struct nlattr **tb, unsigned int header,
struct netlink_ext_ack *extack)
{
struct phy_device *phydev;
@@ -225,8 +225,8 @@ struct phy_device *ethnl_req_get_phydev(const struct ethnl_req_info *req_info,
return req_info->dev->phydev;

phydev = phy_link_topo_get_phy(req_info->dev, req_info->phy_index);
- if (!phydev) {
- NL_SET_ERR_MSG_ATTR(extack, header,
+ if (!phydev && tb) {
+ NL_SET_ERR_MSG_ATTR(extack, tb[header],
"no phy matching phyindex");
return ERR_PTR(-ENODEV);
}
diff --git a/net/ethtool/netlink.h b/net/ethtool/netlink.h
index ff69ca0715de..ec6ab5443a6f 100644
--- a/net/ethtool/netlink.h
+++ b/net/ethtool/netlink.h
@@ -275,7 +275,8 @@ static inline void ethnl_parse_header_dev_put(struct ethnl_req_info *req_info)
* ethnl_req_get_phydev() - Gets the phy_device targeted by this request,
* if any. Must be called under rntl_lock().
* @req_info: The ethnl request to get the phy from.
- * @header: The netlink header, used for error reporting.
+ * @tb: The netlink attributes array, for error reporting.
+ * @header: The netlink header index, used for error reporting.
* @extack: The netlink extended ACK, for error reporting.
*
* The caller must hold RTNL, until it's done interacting with the returned
@@ -289,7 +290,7 @@ static inline void ethnl_parse_header_dev_put(struct ethnl_req_info *req_info)
* is returned.
*/
struct phy_device *ethnl_req_get_phydev(const struct ethnl_req_info *req_info,
- const struct nlattr *header,
+ struct nlattr **tb, unsigned int header,
struct netlink_ext_ack *extack);

/**
diff --git a/net/ethtool/phy.c b/net/ethtool/phy.c
index ed8f690f6bac..e067cc234419 100644
--- a/net/ethtool/phy.c
+++ b/net/ethtool/phy.c
@@ -125,7 +125,7 @@ static int ethnl_phy_parse_request(struct ethnl_req_info *req_base,
struct phy_req_info *req_info = PHY_REQINFO(req_base);
struct phy_device *phydev;

- phydev = ethnl_req_get_phydev(req_base, tb[ETHTOOL_A_PHY_HEADER],
+ phydev = ethnl_req_get_phydev(req_base, tb, ETHTOOL_A_PHY_HEADER,
extack);
if (!phydev)
return 0;
diff --git a/net/ethtool/plca.c b/net/ethtool/plca.c
index d95d92f173a6..e1f7820a6158 100644
--- a/net/ethtool/plca.c
+++ b/net/ethtool/plca.c
@@ -62,7 +62,7 @@ static int plca_get_cfg_prepare_data(const struct ethnl_req_info *req_base,
struct phy_device *phydev;
int ret;

- phydev = ethnl_req_get_phydev(req_base, tb[ETHTOOL_A_PLCA_HEADER],
+ phydev = ethnl_req_get_phydev(req_base, tb, ETHTOOL_A_PLCA_HEADER,
info->extack);
// check that the PHY device is available and connected
if (IS_ERR_OR_NULL(phydev)) {
@@ -152,7 +152,7 @@ ethnl_set_plca(struct ethnl_req_info *req_info, struct genl_info *info)
bool mod = false;
int ret;

- phydev = ethnl_req_get_phydev(req_info, tb[ETHTOOL_A_PLCA_HEADER],
+ phydev = ethnl_req_get_phydev(req_info, tb, ETHTOOL_A_PLCA_HEADER,
info->extack);
// check that the PHY device is available and connected
if (IS_ERR_OR_NULL(phydev))
@@ -211,7 +211,7 @@ static int plca_get_status_prepare_data(const struct ethnl_req_info *req_base,
struct phy_device *phydev;
int ret;

- phydev = ethnl_req_get_phydev(req_base, tb[ETHTOOL_A_PLCA_HEADER],
+ phydev = ethnl_req_get_phydev(req_base, tb, ETHTOOL_A_PLCA_HEADER,
info->extack);
// check that the PHY device is available and connected
if (IS_ERR_OR_NULL(phydev)) {
diff --git a/net/ethtool/pse-pd.c b/net/ethtool/pse-pd.c
index 2819e2ba6be2..4f6b99eab2a6 100644
--- a/net/ethtool/pse-pd.c
+++ b/net/ethtool/pse-pd.c
@@ -64,7 +64,7 @@ static int pse_prepare_data(const struct ethnl_req_info *req_base,
if (ret < 0)
return ret;

- phydev = ethnl_req_get_phydev(req_base, tb[ETHTOOL_A_PSE_HEADER],
+ phydev = ethnl_req_get_phydev(req_base, tb, ETHTOOL_A_PSE_HEADER,
info->extack);
if (IS_ERR(phydev))
return -ENODEV;
@@ -261,7 +261,7 @@ ethnl_set_pse(struct ethnl_req_info *req_info, struct genl_info *info)
struct phy_device *phydev;
int ret;

- phydev = ethnl_req_get_phydev(req_info, tb[ETHTOOL_A_PSE_HEADER],
+ phydev = ethnl_req_get_phydev(req_info, tb, ETHTOOL_A_PSE_HEADER,
info->extack);
ret = ethnl_set_pse_validate(phydev, info);
if (ret)
diff --git a/net/ethtool/stats.c b/net/ethtool/stats.c
index 038a2558f052..3ca8eb2a3b31 100644
--- a/net/ethtool/stats.c
+++ b/net/ethtool/stats.c
@@ -138,7 +138,7 @@ static int stats_prepare_data(const struct ethnl_req_info *req_base,
struct phy_device *phydev;
int ret;

- phydev = ethnl_req_get_phydev(req_base, tb[ETHTOOL_A_STATS_HEADER],
+ phydev = ethnl_req_get_phydev(req_base, tb, ETHTOOL_A_STATS_HEADER,
info->extack);
if (IS_ERR(phydev))
return PTR_ERR(phydev);
diff --git a/net/ethtool/strset.c b/net/ethtool/strset.c
index 6b76c05caba4..f6a67109beda 100644
--- a/net/ethtool/strset.c
+++ b/net/ethtool/strset.c
@@ -309,7 +309,7 @@ static int strset_prepare_data(const struct ethnl_req_info *req_base,
return 0;
}

- phydev = ethnl_req_get_phydev(req_base, tb[ETHTOOL_A_HEADER_FLAGS],
+ phydev = ethnl_req_get_phydev(req_base, tb, ETHTOOL_A_HEADER_FLAGS,
info->extack);

/* phydev can be NULL, check for errors only */
--
2.48.1