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From: geert@linux-m68k.org (Geert Uytterhoeven)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/2] Initial support for Allwinner's Security ID fuses
Date: Wed, 26 Jun 2013 11:22:30 +0200	[thread overview]
Message-ID: <CAMuHMdVkyTXDsEyAvD4pHBiXHADbncGUHeeqXBCQMbU7t6TTDQ@mail.gmail.com> (raw)
In-Reply-To: <20130624160440.GA15201@kroah.com>

On Mon, Jun 24, 2013 at 6:04 PM, Greg KH <gregkh@linuxfoundation.org> wrote:
> On Mon, Jun 24, 2013 at 11:29:42AM +0200, Maxime Ripard wrote:
>> On Mon, Jun 17, 2013 at 03:58:47PM -0700, Greg KH wrote:
>> > On Mon, Jun 17, 2013 at 10:59:37PM +0200, Oliver Schinagl wrote:
>> > > +static int __init sunxi_sid_probe(struct platform_device *pdev)
>> > > +{
>> > > + u8 entropy[SID_SIZE];
>> > > + unsigned int i;
>> > > + struct resource *res;
>> > > + void __iomem *sid_reg_base;
>> > > + int ret;
>> > > +
>> > > + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> > > + sid_reg_base = devm_ioremap_resource(&pdev->dev, res);
>> > > + if (IS_ERR(sid_reg_base))
>> > > +         return PTR_ERR(sid_reg_base);
>> > > + platform_set_drvdata(pdev, sid_reg_base);
>> > > +
>> > > + ret = device_create_bin_file(&pdev->dev, &sid_bin_attr);
>> > > + if (ret)
>> > > +         return ret;
>> >
>> > You just raced with userspace, having the file show up after the device
>> > was announced to users that it was there.  Please use the proper device
>> > file api to add default attributes to prevent this from happening.
>>
>> Sorry if the question looks dumb, but what kind of race can we generate
>> here?
>
> Userspace gets told about the device from the driver core, udev runs and
> reads all of the attributes, then your probe function comes along and
> adds a new attribute.  Userspace will then not know about it at all.
>
>> The device_create_bin_file is the last call that we make (if we except
>> the entropy stuff, but it doesn't really matter here), so after we
>> created the file, we have everything properly initialised so that our
>> functions can be called, right?
>>
>> And another dumb question for you, what is the "proper device file API"
>> you are referring to ? :)
>
> Please read Documentation/driver_model/device.txt and see the section on
> Attributes for what to do.  If you have specific questions after reading
> that, please let me know.

Woops, then we have plenty of existing drivers to fix, e.g. all/most RTC drivers
exposing an NVRAM file through sysfs:

$ git grep -w sysfs_create_bin_file drivers/rtc/
drivers/rtc/rtc-cmos.c: retval = sysfs_create_bin_file(&dev->kobj, &nvram);
drivers/rtc/rtc-ds1305.c: status =
sysfs_create_bin_file(&spi->dev.kobj, &nvram);
drivers/rtc/rtc-ds1307.c: err =
sysfs_create_bin_file(&client->dev.kobj, ds1307->nvram);
drivers/rtc/rtc-ds1511.c: ret = sysfs_create_bin_file(&pdev->dev.kobj,
&ds1511_nvram_attr);
drivers/rtc/rtc-ds1553.c: ret = sysfs_create_bin_file(&pdev->dev.kobj,
&ds1553_nvram_attr);
drivers/rtc/rtc-ds1742.c: ret = sysfs_create_bin_file(&pdev->dev.kobj,
&pdata->nvram_attr);
drivers/rtc/rtc-m48t59.c: ret = sysfs_create_bin_file(&pdev->dev.kobj,
&m48t59_nvram_attr);
drivers/rtc/rtc-rp5c01.c: error =
sysfs_create_bin_file(&dev->dev.kobj, &priv->nvram_attr);
drivers/rtc/rtc-stk17ta8.c: ret =
sysfs_create_bin_file(&pdev->dev.kobj, &stk17ta8_nvram_attr);
drivers/rtc/rtc-tx4939.c: ret = sysfs_create_bin_file(&pdev->dev.kobj,
&tx4939_rtc_nvram_attr);

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

  parent reply	other threads:[~2013-06-26  9:22 UTC|newest]

Thread overview: 70+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-06-17 20:59 [PATCH 0/2] v4 Driver for Allwinner sunxi Security ID Oliver Schinagl
2013-06-17 20:59 ` [PATCH 1/2] Initial support for Allwinner's Security ID fuses Oliver Schinagl
2013-06-17 21:06   ` Tomasz Figa
2013-06-17 22:58   ` Greg KH
2013-06-17 23:23     ` [linux-sunxi] " Henrik Nordström
2013-06-24  9:29     ` Maxime Ripard
2013-06-24 16:04       ` Greg KH
2013-06-24 17:11         ` Oliver Schinagl
2013-06-24 18:15           ` Greg KH
2013-06-24 21:21             ` Oliver Schinagl
2013-06-24 21:46               ` Greg KH
2013-06-26  8:32                 ` Oliver Schinagl
2013-06-26 17:51                   ` Greg KH
2013-07-05  7:24                     ` Oliver Schinagl
2013-07-06 19:36                       ` Greg KH
2013-07-07  0:17                         ` Greg KH
2013-07-15 21:16                         ` [linux-sunxi] " Oliver Schinagl
2013-07-16  6:41                           ` Greg KH
2013-07-16 21:02                             ` Oliver Schinagl
2013-07-17  4:20                               ` Greg KH
2013-07-17 11:46                             ` Maxime Ripard
2013-07-17 16:17                               ` Greg KH
2013-07-19  9:42                                 ` Maxime Ripard
2013-07-19 23:49                                   ` Greg KH
2013-07-30 13:22                                     ` Oliver Schinagl
2013-07-30 14:20                                       ` Greg KH
2013-07-30 17:39                                         ` Oliver Schinagl
2013-06-26  9:10                 ` Russell King - ARM Linux
2013-06-26 17:51                   ` Greg KH
2013-06-24 21:04         ` Maxime Ripard
2013-06-26  9:22         ` Geert Uytterhoeven [this message]
2013-06-26 17:49           ` Greg KH
2013-06-18  5:41   ` Andy Shevchenko
  -- strict thread matches above, loose matches on Subject: below --
2013-08-27 14:13 [PATCHv5 0/2] Driver for Allwinner sunxi Security ID oliver+list at schinagl.nl
2013-08-27 14:13 ` [PATCH 1/2] Initial support for Allwinner's Security ID fuses oliver+list at schinagl.nl
2013-08-27 15:42   ` Maxime Ripard
2013-06-14 23:16 [PATCH 0/2] v3 Driver for Allwinner sunxi Security ID Oliver Schinagl
2013-06-14 23:16 ` [PATCH 1/2] Initial support for Allwinner's Security ID fuses Oliver Schinagl
2013-06-15  2:14   ` Andy Shevchenko
2013-06-15  9:34     ` Oliver Schinagl
2013-06-15 10:28   ` Tomasz Figa
2013-06-17 10:36     ` Oliver Schinagl
2013-06-17 11:25       ` Russell King - ARM Linux
2013-06-17 11:32         ` Oliver Schinagl
2013-06-17 11:51       ` Maxime Ripard
2013-06-17 12:04         ` Oliver Schinagl
2013-06-17 12:51       ` Tomasz Figa
2013-06-17 13:10         ` Oliver Schinagl
2013-06-17 13:23           ` Tomasz Figa
2013-06-17 13:47             ` Oliver Schinagl
2013-06-02 14:58 [PATCH 0/2] v2 Driver for Allwinner sunxi Security ID Oliver Schinagl
2013-06-02 14:58 ` [PATCH 1/2] Initial support for Allwinner's Security ID fuses Oliver Schinagl
2013-06-02 15:09   ` Russell King - ARM Linux
2013-06-02 15:21     ` Oliver Schinagl
2013-06-06 19:16   ` Andy Shevchenko
2013-06-10 21:43     ` Oliver Schinagl
2013-06-11 10:51       ` Andy Shevchenko
2013-05-17 13:35 [PATCH 0/2] Driver for Allwinner sunxi Security ID Oliver Schinagl
2013-05-17 13:35 ` [PATCH 1/2] Initial support for Allwinner's Security ID fuses Oliver Schinagl
2013-05-17 13:45   ` Arnd Bergmann
2013-05-17 18:54     ` Oliver Schinagl
2013-05-17 21:18   ` Maxime Ripard
2013-05-18 17:19     ` Oliver Schinagl
2013-05-19 15:22       ` Maxime Ripard
2013-05-24 21:50       ` Oliver Schinagl
2013-05-25 12:22         ` Maxime Ripard
2013-05-25 19:25           ` Oliver Schinagl
2013-05-26  9:35             ` Maxime Ripard
2013-05-23  7:56   ` Linus Walleij
2013-05-23  8:10     ` Oliver Schinagl
2013-05-23  8:20       ` Linus Walleij
2013-05-23 14:58       ` Maxime Ripard
2013-05-23 15:05         ` Oliver Schinagl
2013-05-23 15:27           ` Maxime Ripard

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