linux-kernel - [PATCH] leds: lp5523: fix out-of-bounds bug in lp5523

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Message-Id: <20211025122346.28771-1-maarten.zanders@mind.be>
Date:   Mon, 25 Oct 2021 14:23:46 +0200
From:   Maarten Zanders <maarten.zanders@...d.be>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Maarten Zanders <maarten.zanders@...d.be>, stable@...r.kernel.org,
        dmurphy@...com, milo.kim@...com,
        Arne Staessen <a.staessen@...evic.com>,
        Pavel Machek <pavel@....cz>, linux-leds@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] leds: lp5523: fix out-of-bounds bug in lp5523_selftest()

When not all LED channels of the device are configured in OF, the
array size of pdata->led_config is smaller than the max number of
channels on the device. Subsequent accesses to pdata->led_config[i]
are going beyond the bounds of the allocated array. The check on
the configured led_current is also invalid, resulting in erroneous
test results for this function.

There is a potential for LED overcurrent conditions since the
test current will be set to values from these out-of-bound regions.
For the test, the PWM is set to 100%, although for a short amount
of time.

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 configurations might depend on this to disable
a channel.

Cc: <stable@...r.kernel.org>
Cc: <dmurphy@...com>
Cc: <milo.kim@...com>
Reported-by: Arne Staessen <a.staessen@...evic.com>
Signed-off-by: Maarten Zanders <maarten.zanders@...d.be>
---
 drivers/leds/leds-lp5523.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/leds/leds-lp5523.c b/drivers/leds/leds-lp5523.c
index b1590cb4a188..f3782759c8d8 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 +612,20 @@ 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);
@@ -640,12 +640,12 @@ static ssize_t lp5523_selftest(struct device *dev,
 			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,
+		lp55xx_write(chip, LP5523_REG_LED_CURRENT_BASE + led->chan_nr,
 			led->led_current);
 		led++;
 	}
-- 
2.31.1