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SubjectRe: [PATCH] leds: lp5523: fix out-of-bounds bug in lp5523_selftest()
Hi!

> When not all LED channels of the led chip are configured, the
> sysfs selftest functionality gives erroneous results and tries to
> test all channels of the chip.
> There is a potential for LED overcurrent conditions since the
> test current will be set to values from out-of-bound regions.
>
> It is wrong to use pdata->led_config[i].led_current to skip absent
> channels as led_config[] only contains the configured LED channels.
>
> Instead of iterating over all the physical channels of the device,
> loop over the available LED configurations and use led->chan_nr to
> access the correct i2c registers. Keep the zero-check for the LED
> current as existing users might depend on this to disable a channel.

Thanks, applied, I'll push eventually.

I wonder, should we do these kind of actions on attribute _read_? I'd
preffer some kind of write action to trigger this.

Best regards,
Pavel

> Reported-by: Arne Staessen <a.staessen@televic.com>
> Signed-off-by: Maarten Zanders <maarten.zanders@mind.be>
> ---
> drivers/leds/leds-lp5523.c | 27 +++++++++++++++------------
> 1 file changed, 15 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/leds/leds-lp5523.c b/drivers/leds/leds-lp5523.c
> index 369d40b0b65b..e08e3de1428d 100644
> --- a/drivers/leds/leds-lp5523.c
> +++ b/drivers/leds/leds-lp5523.c
> @@ -581,8 +581,8 @@ static ssize_t lp5523_selftest(struct device *dev,
> struct lp55xx_led *led = i2c_get_clientdata(to_i2c_client(dev));
> struct lp55xx_chip *chip = led->chip;
> struct lp55xx_platform_data *pdata = chip->pdata;
> - int i, ret, pos = 0;
> - u8 status, adc, vdd;
> + int ret, pos = 0;
> + u8 status, adc, vdd, i;
>
> mutex_lock(&chip->lock);
>
> @@ -612,20 +612,21 @@ static ssize_t lp5523_selftest(struct device *dev,
>
> vdd--; /* There may be some fluctuation in measurement */
>
> - for (i = 0; i < LP5523_MAX_LEDS; i++) {
> - /* Skip non-existing channels */
> + for (i = 0; i < pdata->num_channels; i++) {
> + /* Skip disabled channels */
> if (pdata->led_config[i].led_current == 0)
> continue;
>
> /* Set default current */
> - lp55xx_write(chip, LP5523_REG_LED_CURRENT_BASE + i,
> + lp55xx_write(chip, LP5523_REG_LED_CURRENT_BASE + led->chan_nr,
> pdata->led_config[i].led_current);
>
> - lp55xx_write(chip, LP5523_REG_LED_PWM_BASE + i, 0xff);
> + lp55xx_write(chip, LP5523_REG_LED_PWM_BASE + led->chan_nr,
> + 0xff);
> /* let current stabilize 2 - 4ms before measurements start */
> usleep_range(2000, 4000);
> lp55xx_write(chip, LP5523_REG_LED_TEST_CTRL,
> - LP5523_EN_LEDTEST | i);
> + LP5523_EN_LEDTEST | led->chan_nr);
> /* ADC conversion time is 2.7 ms typically */
> usleep_range(3000, 6000);
> ret = lp55xx_read(chip, LP5523_REG_STATUS, &status);
> @@ -633,20 +634,22 @@ static ssize_t lp5523_selftest(struct device *dev,
> goto fail;
>
> if (!(status & LP5523_LEDTEST_DONE))
> - usleep_range(3000, 6000);/* Was not ready. Wait. */
> + usleep_range(3000, 6000); /* Was not ready. Wait. */
>
> ret = lp55xx_read(chip, LP5523_REG_LED_TEST_ADC, &adc);
> if (ret < 0)
> goto fail;
>
> if (adc >= vdd || adc < LP5523_ADC_SHORTCIRC_LIM)
> - pos += sprintf(buf + pos, "LED %d FAIL\n", i);
> + pos += sprintf(buf + pos, "LED %d FAIL\n",
> + led->chan_nr);
>
> - lp55xx_write(chip, LP5523_REG_LED_PWM_BASE + i, 0x00);
> + lp55xx_write(chip, LP5523_REG_LED_PWM_BASE + led->chan_nr,
> + 0x00);
>
> /* Restore current */
> - lp55xx_write(chip, LP5523_REG_LED_CURRENT_BASE + i,
> - led->led_current);
> + lp55xx_write(chip, LP5523_REG_LED_CURRENT_BASE + led->chan_nr,
> + led->led_current);
> led++;
> }
> if (pos == 0)
> --
> 2.37.3

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