linux-kernel - Re: drivers/firmware/google/vpd.c: duplicate sysfs file

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Message-ID: <CABXOdTeBzGMrSquEyhCn1Oh4Fg_AfuoSOgUrtVC+zxLxOxDzmw@mail.gmail.com>
Date:   Mon, 13 Nov 2017 11:09:21 -0800
From:   Guenter Roeck <groeck@...gle.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Randy Dunlap <rdunlap@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guenter Roeck <groeck@...omium.org>,
        Wei-Ning Huang <wnhuang@...gle.com>
Subject: Re: drivers/firmware/google/vpd.c: duplicate sysfs file

On Mon, Nov 13, 2017 at 11:04 AM, Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:
>
> On Mon, Nov 13, 2017 at 10:18:35AM -0800, Randy Dunlap wrote:
> > On 11/13/2017 06:41 AM, Guenter Roeck wrote:
> > >
> > >
> > > On Sun, Nov 12, 2017 at 10:36 PM, Randy Dunlap <rdunlap@...radead.org <mailto:rdunlap@...radead.org>> wrote:
> > >
> > >     sysfs: cannot create duplicate filename '/devices/platform/vpd'
> > >
> > >     on the second load of this driver.  I.e.,
> > >
> > >     modprobe vpd-sysfs
> > >     rmmod vpd-sysfs
> > >     modprobe vpd-sysfs
> > >     [boom]
> > >
> > > Neither the platform device nor the platform driver driver are ever unregistered, so this isn't entirely surprising. I'll try to reproduce and send a patch.
> >
> >
> > Seems to be a common theme:
> >
> > google> grep --color=never "platform.*register" *.c
> > coreboot_table-acpi.c:        return platform_driver_register(&coreboot_table_acpi_driver);
> > coreboot_table-of.c:  return platform_driver_register(&coreboot_table_of_driver);
>
> These are not unloadable (for better or worse) - they do not have
> module_exit() in them.
>
> >
> > gsmi.c:       gsmi_dev.pdev = platform_device_register_full(&gsmi_dev_info);
> > gsmi.c:       platform_device_unregister(gsmi_dev.pdev);
> > gsmi.c:       platform_device_unregister(gsmi_dev.pdev);
> > [looks good]
> >
> > memconsole-coreboot.c:        pdev = platform_device_register_simple("memconsole", -1, NULL, 0);
> > memconsole-coreboot.c:        platform_driver_register(&memconsole_driver);
>
> Same here: not unloadable.
>
> >
> > vpd.c:        pdev = platform_device_register_simple("vpd", -1, NULL, 0);
> > vpd.c:        platform_driver_register(&vpd_driver);
>
> Arguably this should not even be a platform driver, there is no hardware
> behind it. I was planning on purring some notifiers into coreboot table
> driver and using notifiers to attach vpd to them. -ENOTIME though.
>
Two options for now: clean it up and make it unloadable, or make it bool
and drop the exit function. Any preference ?

The problem is easy to reproduce even with the driver is built into
the kernel with a simple unbind/bind sequence. And after the unbind,
it is easy to crash the system since the sysfs attributes are still there.

Guenter