From: Vincent MAILHOL <mailhol.vincent@wanadoo.fr>
To: Andrew Lunn <andrew@lunn.ch>
Cc: linux-can@vger.kernel.org, Marc Kleine-Budde <mkl@pengutronix.de>,
linux-kernel@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
netdev@vger.kernel.org, linux-usb@vger.kernel.org,
Saeed Mahameed <saeed@kernel.org>, Jiri Pirko <jiri@nvidia.com>,
Lukas Magel <lukas.magel@posteo.net>
Subject: Re: [PATCH v4 2/6] can: etas_es58x: add devlink support
Date: Sun, 27 Nov 2022 14:10:32 +0900 [thread overview]
Message-ID: <CAMZ6RqK6AQVsRufw5Jr5aKpPQcy+05jq3TjrKqbaqk7NVgK+_Q@mail.gmail.com> (raw)
In-Reply-To: <Y4JEGYMtIWX9clxo@lunn.ch>
On Tue. 27 Nov. 2022 at 01:51, Andrew Lunn <andrew@lunn.ch> wrote:
> > @@ -2196,11 +2198,12 @@ static struct es58x_device *es58x_init_es58x_dev(struct usb_interface *intf,
> > ops = &es581_4_ops;
> > }
> >
> > - es58x_dev = devm_kzalloc(dev, es58x_sizeof_es58x_device(param),
> > - GFP_KERNEL);
> > - if (!es58x_dev)
> > + devlink = devlink_alloc(&es58x_dl_ops, es58x_sizeof_es58x_device(param),
> > + dev);
> > + if (!devlink)
> > return ERR_PTR(-ENOMEM);
> >
> > + es58x_dev = devlink_priv(devlink);
>
> That is 'interesting'.
Another interesting thing I found is:
https://elixir.bootlin.com/linux/v6.1-rc6/source/drivers/net/ethernet/intel/ice/ice_devlink.c#L866
Because devlink does not have an equivalent to devm_kzalloc(), that
driver uses devm_add_action_or_reset() instead. But any other drivers
will call devlink_free() in their disconnect function. So here, I just
followed the trend.
> Makes me wonder about lifetimes of different
> objects. Previously your es58x_dev structure would disappear when the
> driver is released, or an explicit call to devm_kfree(). Now it
> disappears when devlink_free() is called.
Even before that, this driver used to release es58x_dev in its
disconnect() function. I changed it to use devm_kzalloc() last year
after discovering its existence.
https://git.kernel.org/torvalds/linux/c/6bde4c7fd845
>Any danger of use after free here?
devlink_alloc() allocates one continuous block for both the devlink
and the device priv (struct es58x_dev here):
https://elixir.bootlin.com/linux/v6.1-rc6/source/net/core/devlink.c#L9629
So calling devlink_free() also releases struct es58x_dev.
> USB devices always make me wonder about life times rules since they
> are probably the mode dynamic sort of device the kernel has the
> handle, them just abruptly disappearing.
>
> > es58x_dev->param = param;
> > es58x_dev->ops = ops;
> > es58x_dev->dev = dev;
> > @@ -2247,6 +2250,8 @@ static int es58x_probe(struct usb_interface *intf,
> > if (ret)
> > return ret;
> >
> > + devlink_register(priv_to_devlink(es58x_dev));
> > +
> > for (ch_idx = 0; ch_idx < es58x_dev->num_can_ch; ch_idx++) {
> > ret = es58x_init_netdev(es58x_dev, ch_idx);
> > if (ret) {
> > @@ -2272,8 +2277,10 @@ static void es58x_disconnect(struct usb_interface *intf)
> > dev_info(&intf->dev, "Disconnecting %s %s\n",
> > es58x_dev->udev->manufacturer, es58x_dev->udev->product);
> >
> > + devlink_unregister(priv_to_devlink(es58x_dev));
> > es58x_free_netdevs(es58x_dev);
> > es58x_free_urbs(es58x_dev);
> > + devlink_free(priv_to_devlink(es58x_dev));
> > usb_set_intfdata(intf, NULL);
>
> Should devlink_free() be after usb_set_inftdata()?
A look at
$ git grep -W "usb_set_intfdata(.*NULL)"
shows that the two patterns (freeing before or after
usb_set_intfdata()) coexist.
You are raising an important question here. usb_set_intfdata() does
not have documentation that freeing before it is risky. And the
documentation of usb_driver::disconnect says that:
"@disconnect: Called when the interface is no longer accessible,
usually because its device has been (or is being) disconnected
or the driver module is being unloaded."
Ref: https://elixir.bootlin.com/linux/v6.1-rc6/source/include/linux/usb.h#L1130
So the interface no longer being accessible makes me assume that the
order does not matter. If it indeed matters, then this is a foot gun
and there is some clean-up work waiting for us on many drivers.
@Greg, any thoughts on whether or not the order of usb_set_intfdata()
and resource freeing matters or not?
Yours sincerely,
Vincent Mailhol
next prev parent reply other threads:[~2022-11-27 5:10 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20221104073659.414147-1-mailhol.vincent@wanadoo.fr>
2022-11-13 4:01 ` [PATCH v3 0/3] can: etas_es58x: report firmware, bootloader and hardware version Vincent Mailhol
2022-11-13 4:01 ` [PATCH v3 1/3] USB: core: export usb_cache_string() Vincent Mailhol
2022-11-22 16:00 ` Greg Kroah-Hartman
2022-11-13 4:01 ` [PATCH v3 2/3] can: etas_es58x: export firmware, bootloader and hardware versions in sysfs Vincent Mailhol
2022-11-15 22:47 ` Saeed Mahameed
2022-11-16 0:36 ` Vincent MAILHOL
2022-11-16 23:20 ` Saeed Mahameed
2022-11-13 4:01 ` [PATCH v3 3/3] can: etas_es58x: report firmware-version through ethtool Vincent Mailhol
2022-11-13 16:48 ` [PATCH v3 0/3] can: etas_es58x: report firmware, bootloader and hardware version Andrew Lunn
2022-11-14 16:49 ` Vincent MAILHOL
2022-11-14 17:08 ` Andrew Lunn
2022-11-26 16:22 ` [PATCH v4 0/6] " Vincent Mailhol
2022-11-26 16:22 ` [PATCH v4 1/6] USB: core: export usb_cache_string() Vincent Mailhol
2022-11-26 16:22 ` [PATCH v4 2/6] can: etas_es58x: add devlink support Vincent Mailhol
2022-11-26 16:51 ` Andrew Lunn
2022-11-27 5:10 ` Vincent MAILHOL [this message]
2022-11-27 15:36 ` Alan Stern
2022-11-28 1:34 ` Vincent MAILHOL
2022-11-28 5:32 ` Vincent MAILHOL
2022-11-28 15:50 ` Alan Stern
2022-11-28 23:30 ` Vincent MAILHOL
2022-11-28 13:42 ` Andrew Lunn
2022-11-28 14:29 ` Vincent MAILHOL
2022-11-26 16:22 ` [PATCH v4 3/6] can: etas_es58x: export product information through devlink_ops::info_get() Vincent Mailhol
2022-11-26 17:16 ` Andrew Lunn
2022-11-27 3:42 ` Vincent MAILHOL
2022-11-27 4:31 ` Vincent MAILHOL
2022-11-27 15:07 ` Andrew Lunn
2022-11-28 1:21 ` Vincent MAILHOL
2022-11-28 13:43 ` Andrew Lunn
2022-11-28 13:47 ` Andrew Lunn
2022-11-28 14:43 ` Vincent MAILHOL
2022-11-28 22:27 ` Jakub Kicinski
2022-11-28 23:17 ` Vincent MAILHOL
2022-11-26 16:22 ` [PATCH v4 4/6] can: etas_es58x: remove es58x_get_product_info() Vincent Mailhol
2022-11-28 13:44 ` Andrew Lunn
2022-11-28 14:36 ` Vincent MAILHOL
2022-11-26 16:22 ` [PATCH v4 5/6] can: etas_es58x: report the firmware version through ethtool Vincent Mailhol
2022-11-28 13:44 ` Andrew Lunn
2022-11-28 22:29 ` Jakub Kicinski
2022-11-29 17:12 ` Vincent MAILHOL
2022-11-30 2:31 ` Jakub Kicinski
2022-11-26 16:22 ` [PATCH v4 6/6] Documentation: devlink: add devlink documentation for the etas_es58x driver Vincent Mailhol
2022-11-30 17:46 ` [PATCH v5 0/7] can: etas_es58x: report firmware, bootloader and hardware version Vincent Mailhol
2022-11-30 17:46 ` [PATCH v5 1/7] can: etas_es58x: add devlink support Vincent Mailhol
2022-11-30 17:46 ` [PATCH v5 2/7] can: etas_es58x: add devlink port support Vincent Mailhol
2022-11-30 17:46 ` [PATCH v5 3/7] USB: core: export usb_cache_string() Vincent Mailhol
2022-11-30 17:46 ` [PATCH v5 4/7] net: devlink: add DEVLINK_INFO_VERSION_GENERIC_FW_BOOTLOADER Vincent Mailhol
2022-11-30 17:46 ` [PATCH v5 5/7] can: etas_es58x: export product information through devlink_ops::info_get() Vincent Mailhol
2022-11-30 17:46 ` [PATCH v5 6/7] can: etas_es58x: remove es58x_get_product_info() Vincent Mailhol
2022-11-30 17:46 ` [PATCH v5 7/7] Documentation: devlink: add devlink documentation for the etas_es58x driver Vincent Mailhol
2022-12-02 12:27 ` Marc Kleine-Budde
2022-12-02 13:15 ` Vincent MAILHOL
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAMZ6RqK6AQVsRufw5Jr5aKpPQcy+05jq3TjrKqbaqk7NVgK+_Q@mail.gmail.com \
--to=mailhol.vincent@wanadoo.fr \
--cc=andrew@lunn.ch \
--cc=gregkh@linuxfoundation.org \
--cc=jiri@nvidia.com \
--cc=linux-can@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-usb@vger.kernel.org \
--cc=lukas.magel@posteo.net \
--cc=mkl@pengutronix.de \
--cc=netdev@vger.kernel.org \
--cc=saeed@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).