[PATCH net-next] net: phylink: reject unsupported speed/duplex in ksettings_set() with PHY

From: Nazim Amirul <redacted>

When using ethtool to change speed and duplex on a phylink-managed
interface with a PHY attached, the requested speed/duplex combination
is not validated against the MAC's supported capabilities before being
passed down to the PHY layer.

commit df0acdc59b09 ("net: phylink: fix ksettings_set() ethtool call")
and commit 03c44a21d033 ("net: phylink: actually fix ksettings_set()
ethtool call") introduced masking of the PHY advertising modes against
pl->supported, but did not add an explicit check that the requested
speed/duplex itself is within the MAC's capability set.

The AUTONEG_DISABLE path in the non-PHY case already uses
phy_caps_lookup() to validate speed/duplex against pl->supported.
Extend the same validation to the pl->phydev path so that ethtool
requests for unsupported speed/duplex combinations are rejected with
-EINVAL before reaching the PHY layer.

Signed-off-by: Nazim Amirul <redacted>
---
 drivers/net/phy/phylink.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index 087ac63f9193..22f9bbd381bd 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c

@@ -2989,6 +2989,10 @@ int phylink_ethtool_ksettings_set(struct phylink *pl,
 	if (pl->phydev) {
 		struct ethtool_link_ksettings phy_kset = *kset;
 
+		if (!phy_caps_lookup(kset->base.speed, kset->base.duplex,
+				     pl->supported, true))
+			return -EINVAL;
+
 		linkmode_and(phy_kset.link_modes.advertising,
 			     phy_kset.link_modes.advertising,
 			     pl->supported);

-- 
2.43.7