Re: [PATCH net-next 11/13] netlink: add net device refcount tracker to struct ethnl_req_info

On Tue, Jan 4, 2022 at 8:07 AM Johannes Berg [off-list ref] wrote:

Hi Eric,

quoted

quoted

quoted

@@ -624,6 +625,7 @@ static void ethnl_default_notify(struct net_device *dev, unsigned int cmd,
      }

      req_info->dev = dev;
+     netdev_tracker_alloc(dev, &req_info->dev_tracker, GFP_KERNEL);
      req_info->flags |= ETHTOOL_FLAG_COMPACT_BITSETS;

I may have missed a follow-up patch (did a search on netdev now, but
...), but I'm hitting warnings from this and I'm not sure it's right?

This req_info is just allocated briefly and freed again, and I'm not
even sure there's a dev_get/dev_put involved here, I didn't see any?

We had a fix.

commit 34ac17ecbf575eb079094d44f1bd30c66897aa21
Author: Eric Dumazet [off-list ref]
Date:   Tue Dec 14 00:42:30 2021 -0800

    ethtool: use ethnl_parse_header_dev_put()

Hmm. I have this in my tree, and I don't think it affected
ethnl_default_notify() anyway?

Strange, syzbot have not reported anything there.

ethnl_parse_header_dev_get() needs to take a ref, but
indeed ethnl_default_notify() does its own allocation/freeing.

diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index ea23659fab28..5fe8f4ae2ceb 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c

@@ -627,7 +627,6 @@ static void ethnl_default_notify(struct net_device

*dev, unsigned int cmd,
        }

        req_info->dev = dev;
-       netdev_tracker_alloc(dev, &req_info->dev_tracker, GFP_KERNEL);
        req_info->flags |= ETHTOOL_FLAG_COMPACT_BITSETS;

        ethnl_init_reply_data(reply_data, ops, dev);