net: ethtool: pse-pd: Fix possible null-deref

Fix a possible null dereference when a PSE supports both c33 and PoDL, but
only one of the netlink attributes is specified. The c33 or PoDL PSE
capabilities are already validated in the ethnl_set_pse_validate() call.

Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
Reported-by: Jakub Kicinski <kuba@kernel.org>
Closes: https://lore.kernel.org/netdev/20240705184116.13d8235a@kernel.org/
Fixes: 4d18e3d ("net: ethtool: pse-pd: Expand pse commands with the PSE PoE interface")
Link: https://patch.msgid.link/20240711-fix_pse_pd_deref-v3-2-edd78fc4fe42@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kmaincent

net/ethtool/pse-pd.c

@@ -178,9 +178,9 @@ ethnl_set_pse(struct ethnl_req_info *req_info, struct genl_info *info)
 
 	phydev = dev->phydev;
 	/* These values are already validated by the ethnl_pse_set_policy */
-	if (pse_has_podl(phydev->psec))
+	if (tb[ETHTOOL_A_PODL_PSE_ADMIN_CONTROL])
 		config.podl_admin_control = nla_get_u32(tb[ETHTOOL_A_PODL_PSE_ADMIN_CONTROL]);
-	if (pse_has_c33(phydev->psec))
+	if (tb[ETHTOOL_A_C33_PSE_ADMIN_CONTROL])
 		config.c33_admin_control = nla_get_u32(tb[ETHTOOL_A_C33_PSE_ADMIN_CONTROL]);
 
 	/* Return errno directly - PSE has no notification