From: Andy Shevchenko <andriy.shevchenko@intel.com>
To: David Carlier <devnexen@gmail.com>
Cc: "Jonathan Cameron" <jic23@kernel.org>,
"Ariana Lazar" <ariana.lazar@microchip.com>,
"David Lechner" <dlechner@baylibre.com>,
"Nuno Sá" <nuno.sa@analog.com>,
"Andy Shevchenko" <andy@kernel.org>,
linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH] iio: dac: mcp47feb02: reject out-of-range raw values
Date: Sun, 25 Oct 2026 22:37:22 +0200 [thread overview]
Message-ID: <at5ogu8JaXFbQpHg@ashevche-desk.local> (raw)
In-Reply-To: <20261024214423.865635-1-devnexen@gmail.com>
On Sat, Oct 24, 2026 at 10:44:23PM +0100, David Carlier wrote:
> mcp47feb02_write_raw() writes the user supplied raw value to the DAC
> register without checking it against the chip resolution. The parts
> are 8, 10 or 12 bit, and the bits above the resolution are not
> implemented, so writing 300 to out_voltage0_raw on an 8-bit part sets
> the output to code 44 instead of failing, and -1 is written as 0xffff.
>
> The out-of-range value is also cached in dac_data, so it is written
> back on resume and stored to EEPROM by store_eeprom.
>
> Return -EINVAL for values outside [0, 2^resolution - 1].
>
> Found by code inspection. Build tested with W=1 (=m and =y) only;
> no hardware was available for runtime testing.
...
> case IIO_CHAN_INFO_RAW:
> + if (val < 0 || val >= BIT(data->chip_features->resolution))
If resolution is 32, this will suck. (Yes, this is a bit theoretical case.)
> + return -EINVAL;
Not sure about this error code. Do other IIO drivers use same in the similar
situation?
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2026-10-25 20:37 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-24 21:44 David Carlier
2026-10-25 10:17 ` Joshua Crofts
2026-10-25 20:37 ` Andy Shevchenko [this message]
[not found] ` <CA+XhMqx5jusLqo8G2XCY9gy_P=3-jAwTacgzrR4XFyjpagi8dA@mail.gmail.com>
2026-10-25 21:07 ` Andy Shevchenko
[not found] ` <CA+XhMqzZZyN80nP2ER3jyTsM9UC2xMRLiqdCsAtp+K=hDbqtQg@mail.gmail.com>
2026-10-25 21:25 ` Andy Shevchenko
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