From: Matti Vaittinen <mazziesaccount@gmail.com>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: "Alexandre Belloni" <alexandre.belloni@bootlin.com>,
linux-iio@vger.kernel.org,
"Gwendal Grignou" <gwendal@chromium.org>,
linux-kernel@vger.kernel.org,
"Paul Cercueil" <paul@crapouillou.net>,
"Miquel Raynal" <miquel.raynal@bootlin.com>,
"Guenter Roeck" <groeck@chromium.org>,
chrome-platform@lists.linux.dev,
"Lars-Peter Clausen" <lars@metafoo.de>,
"Miaoqian Lin" <linmq006@gmail.com>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Alexandru Ardelean" <alexandru.ardelean@analog.com>,
"Mihail Chindris" <mihail.chindris@analog.com>,
"Michael Hennerich" <Michael.Hennerich@analog.com>,
"Cosmin Tanislav" <cosmin.tanislav@analog.com>,
"Nathan Chancellor" <nathan@kernel.org>,
"Benson Leung" <bleung@chromium.org>,
linux-arm-kernel@lists.infradead.org,
"Matti Vaittinen" <matti.vaittinen@fi.rohmeurope.com>,
"Eugen Hristev" <eugen.hristev@microchip.com>,
"Claudiu Beznea" <claudiu.beznea@microchip.com>,
"Jonathan Cameron" <jic23@kernel.org>
Subject: Re: [RFT PATCH v3 10/10] iio: Don't silently expect attribute types
Date: Mon, 3 Oct 2022 12:02:56 +0300 [thread overview]
Message-ID: <7ae09809-4f3c-9872-5a87-0a05e73d39b4@gmail.com> (raw)
In-Reply-To: <b36ee317-abfe-9f55-70b5-bbf3138f50c0@gmail.com>
On 10/3/22 11:58, Matti Vaittinen wrote:
> Hi Andy,
>
> Thanks for taking the time to review :) Much appreciated.
>
> On 10/3/22 11:43, Andy Shevchenko wrote:
>> On Mon, Oct 03, 2022 at 11:13:53AM +0300, Matti Vaittinen wrote:
>>> The iio_triggered_buffer_setup_ext() and the
>>> devm_iio_kfifo_buffer_setup_ext() were changed by
>>> commit 15097c7a1adc ("iio: buffer: wrap all buffer attributes into
>>> iio_dev_attr")
>>> to silently expect that all attributes given in buffer_attrs array are
>>> device-attributes. This expectation was not forced by the API - and some
>>> drivers did register attributes created by IIO_CONST_ATTR().
>>>
>>> When using IIO_CONST_ATTRs the added attribute "wrapping" does not copy
>>> the pointer to stored string constant and when the sysfs file is read
>>> the
>>> kernel will access to invalid location.
>>>
>>> Change the function signatures to expect an array of iio_dev_attrs to
>>> avoid similar errors in the future.
>>
>> ...
>>
>>> + attr[ARRAY_SIZE(iio_buffer_attrs) + i] =
>>> + (struct attribute *)&id_attr->dev_attr.attr;
>>
>> ...and explicit casting here. Isn't attr is already of a struct
>> attribute?
>
> I am glad you asked :)
> This is one of the "things" I was not really happy about. Here we hide
> the fact that our array is full of pointers to _const_ data. If we don't
> cast the compiler points this out. Old code did the same thing but it
> did this by just doing a memcpy for the pointers - which I personally
> consider even worse as it gets really easy to miss this. The cast at
> least hints there is something slightly "fishy" going on.
>
> My "gut feeling" about the correct fix is we should check if some
> attributes in the array (stored to the struct here) actually need to be
> modified later (which I doubt). If I was keen on betting I'd bet we
> could switch the struct definition to also contain pointers to const
> attributes. I am afraid this would mean quite a few more changes to the
> function signatures (changing struct attribute * to const struct
> attribute *) here and there - and possibly also require some changes to
> drivers. Thus I didn't even look at that option in the scope of this
> fix. It should probably be a separate refactoring series. But yes - this
> cast should catch attention as it did.
>
Actually, now that you pointed it out - do you think this would warrant
a FIXME comment?
> Yours,
> -- Matti Vaittinen
>
--
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland
~~ When things go utterly wrong vim users can always type :help! ~~
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next prev parent reply other threads:[~2022-10-03 9:04 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-03 8:09 [PATCH v3 00/10] iio: Fix unsafe buffer attributes Matti Vaittinen
2022-10-03 8:11 ` [PATCH v3 04/10] iio: at91-sama5d2_adc: " Matti Vaittinen
2022-10-06 8:34 ` Claudiu.Beznea
2022-10-16 11:14 ` Jonathan Cameron
2022-10-03 8:13 ` [PATCH v3 09/10] iio: at91-sama5d2_adc: Use IIO_STATIC_CONST_DEVICE_ATTR() Matti Vaittinen
2022-10-06 8:35 ` Claudiu.Beznea
2022-10-03 8:13 ` [RFT PATCH v3 10/10] iio: Don't silently expect attribute types Matti Vaittinen
2022-10-03 8:43 ` Andy Shevchenko
2022-10-03 8:58 ` Matti Vaittinen
2022-10-03 9:02 ` Matti Vaittinen [this message]
2022-10-03 9:39 ` Andy Shevchenko
2022-10-03 9:42 ` Andy Shevchenko
2022-10-06 8:35 ` Claudiu.Beznea
2022-10-06 12:53 ` Matti Vaittinen
2022-10-09 17:38 ` Jonathan Cameron
2022-10-10 9:36 ` Matti Vaittinen
2022-11-05 14:45 ` Jonathan Cameron
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