net: ethtool: Don't call .cleanup_data when prepare_data fails

JIRA: https://issues.redhat.com/browse/RHEL-75603

commit 4f038a6
Author: Maxime Chevallier <maxime.chevallier@bootlin.com>
Date:   Mon Apr 7 15:05:10 2025 +0200

    net: ethtool: Don't call .cleanup_data when prepare_data fails

    There's a consistent pattern where the .cleanup_data() callback is
    called when .prepare_data() fails, when it should really be called to
    clean after a successful .prepare_data() as per the documentation.

    Rewrite the error-handling paths to make sure we don't cleanup
    un-prepared data.

    Fixes: c781ff1 ("ethtool: Allow network drivers to dump arbitrary EEPROM data")
    Reviewed-by: Kory Maincent <kory.maincent@bootlin.com>
    Reviewed-by: Simon Horman <horms@kernel.org>
    Reviewed-by: Michal Kubecek <mkubecek@suse.cz>
    Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
    Link: https://patch.msgid.link/20250407130511.75621-1-maxime.chevallier@bootlin.com
    Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Signed-off-by: Mohammad Heib <mheib@redhat.com>

Author: mohammadheib

net/ethtool/netlink.c

@@ -493,7 +493,7 @@ static int ethnl_default_doit(struct sk_buff *skb, struct genl_info *info)
 	ret = ops->prepare_data(req_info, reply_data, info);
 	rtnl_unlock();
 	if (ret < 0)
-		goto err_cleanup;
+		goto err_dev;
 	ret = ops->reply_size(req_info, reply_data);
 	if (ret < 0)
 		goto err_cleanup;
@@ -551,7 +551,7 @@ static int ethnl_default_dump_one(struct sk_buff *skb, struct net_device *dev,
 	ret = ctx->ops->prepare_data(ctx->req_info, ctx->reply_data, info);
 	rtnl_unlock();
 	if (ret < 0)
-		goto out;
+		goto out_cancel;
 	ret = ethnl_fill_reply_header(skb, dev, ctx->ops->hdr_attr);
 	if (ret < 0)
 		goto out;
@@ -560,6 +560,7 @@ static int ethnl_default_dump_one(struct sk_buff *skb, struct net_device *dev,
 out:
 	if (ctx->ops->cleanup_data)
 		ctx->ops->cleanup_data(ctx->reply_data);
+out_cancel:
 	ctx->reply_data->dev = NULL;
 	if (ret < 0)
 		genlmsg_cancel(skb, ehdr);
@@ -780,7 +781,7 @@ static void ethnl_default_notify(struct net_device *dev, unsigned int cmd,
 	ethnl_init_reply_data(reply_data, ops, dev);
 	ret = ops->prepare_data(req_info, reply_data, &info);
 	if (ret < 0)
-		goto err_cleanup;
+		goto err_rep;
 	ret = ops->reply_size(req_info, reply_data);
 	if (ret < 0)
 		goto err_cleanup;
@@ -815,6 +816,7 @@ static void ethnl_default_notify(struct net_device *dev, unsigned int cmd,
 err_cleanup:
 	if (ops->cleanup_data)
 		ops->cleanup_data(reply_data);
+err_rep:
 	kfree(reply_data);
 	kfree(req_info);
 	return;