2019-09-29 16:48:51

by Yizhuo Zhai

Subject: [PATCH] iio: adc: meson-saradc: Variables could be uninitalized if regmap_read() fails

Several functions in this file are trying to use regmap_read() to
initialize the specific variable, however, if regmap_read() fails,
the variable could be uninitialized but used directly, which is
potentially unsafe. The return value of regmap_read() should be
checked and handled.

Signed-off-by: Yizhuo <[email protected]>
---
drivers/iio/adc/meson_saradc.c | 30 ++++++++++++++++++++++++------
1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/drivers/iio/adc/meson_saradc.c b/drivers/iio/adc/meson_saradc.c
index 7b28d045d271..4b6c2983ef39 100644
--- a/drivers/iio/adc/meson_saradc.c
+++ b/drivers/iio/adc/meson_saradc.c
@@ -323,6 +323,7 @@ static int meson_sar_adc_wait_busy_clear(struct iio_dev *indio_dev)
{
struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
int regval, timeout = 10000;
+ int ret;

/*
* NOTE: we need a small delay before reading the status, otherwise
@@ -331,7 +332,9 @@ static int meson_sar_adc_wait_busy_clear(struct iio_dev *indio_dev)
*/
do {
udelay(1);
- regmap_read(priv->regmap, MESON_SAR_ADC_REG0, &regval);
+ ret = regmap_read(priv->regmap, MESON_SAR_ADC_REG0, &regval);
+ if (ret)
+ return ret;
} while (FIELD_GET(MESON_SAR_ADC_REG0_BUSY_MASK, regval) && timeout--);

if (timeout < 0)
@@ -346,6 +349,7 @@ static int meson_sar_adc_read_raw_sample(struct iio_dev *indio_dev,
{
struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
int regval, fifo_chan, fifo_val, count;
+ int ret;

if(!wait_for_completion_timeout(&priv->done,
msecs_to_jiffies(MESON_SAR_ADC_TIMEOUT)))
@@ -358,7 +362,10 @@ static int meson_sar_adc_read_raw_sample(struct iio_dev *indio_dev,
return -EINVAL;
}

- regmap_read(priv->regmap, MESON_SAR_ADC_FIFO_RD, &regval);
+ ret = regmap_read(priv->regmap, MESON_SAR_ADC_FIFO_RD, &regval);
+ if (ret)
+ return ret;
+
fifo_chan = FIELD_GET(MESON_SAR_ADC_FIFO_RD_CHAN_ID_MASK, regval);
if (fifo_chan != chan->address) {
dev_err(&indio_dev->dev,
@@ -491,6 +498,7 @@ static int meson_sar_adc_lock(struct iio_dev *indio_dev)
{
struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
int val, timeout = 10000;
+ int ret;

mutex_lock(&indio_dev->mlock);

@@ -506,7 +514,10 @@ static int meson_sar_adc_lock(struct iio_dev *indio_dev)
*/
do {
udelay(1);
- regmap_read(priv->regmap, MESON_SAR_ADC_DELAY, &val);
+ ret = regmap_read(priv->regmap,
+ MESON_SAR_ADC_DELAY, &val);
+ if (ret)
+ return ret;
} while (val & MESON_SAR_ADC_DELAY_BL30_BUSY && timeout--);

if (timeout < 0) {
@@ -771,7 +782,7 @@ static int meson_sar_adc_init(struct iio_dev *indio_dev)
{
struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
int regval, i, ret;
-
+ int ret;
/*
* make sure we start at CH7 input since the other muxes are only used
* for internal calibration.
@@ -784,7 +795,10 @@ static int meson_sar_adc_init(struct iio_dev *indio_dev)
* BL30 to make sure BL30 gets the values it expects when
* reading the temperature sensor.
*/
- regmap_read(priv->regmap, MESON_SAR_ADC_REG3, &regval);
+ ret = regmap_read(priv->regmap, MESON_SAR_ADC_REG3, &regval);
+ if (ret)
+ return ret;
+
if (regval & MESON_SAR_ADC_REG3_BL30_INITIALIZED)
return 0;
}
@@ -1013,8 +1027,12 @@ static irqreturn_t meson_sar_adc_irq(int irq, void *data)
struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
unsigned int cnt, threshold;
u32 regval;
+ int ret;
+
+ ret = regmap_read(priv->regmap, MESON_SAR_ADC_REG0, &regval);
+ if (ret)
+ return ret;

- regmap_read(priv->regmap, MESON_SAR_ADC_REG0, &regval);
cnt = FIELD_GET(MESON_SAR_ADC_REG0_FIFO_COUNT_MASK, regval);
threshold = FIELD_GET(MESON_SAR_ADC_REG0_FIFO_CNT_IRQ_MASK, regval);

--
2.17.1

2019-09-30 21:17:58

by Martin Blumenstingl

Subject: Re: [PATCH] iio: adc: meson-saradc: Variables could be uninitalized if regmap_read() fails

Hi Yizhuo,

thank you for this patch

On Sun, Sep 29, 2019 at 6:48 PM Yizhuo <[email protected]> wrote:
>
> Several functions in this file are trying to use regmap_read() to
> initialize the specific variable, however, if regmap_read() fails,
> the variable could be uninitialized but used directly, which is
> potentially unsafe. The return value of regmap_read() should be
> checked and handled.
the meson_saradc driver is using a MMIO regmap so read failures are
unlikely (unless there's a bug in the code somewhere)
did you find these issues with some static code analysis tool or did
you experience a real world problem?

> Signed-off-by: Yizhuo <[email protected]>
> ---
> drivers/iio/adc/meson_saradc.c | 30 ++++++++++++++++++++++++------
> 1 file changed, 24 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/iio/adc/meson_saradc.c b/drivers/iio/adc/meson_saradc.c
> index 7b28d045d271..4b6c2983ef39 100644
> --- a/drivers/iio/adc/meson_saradc.c
> +++ b/drivers/iio/adc/meson_saradc.c
> @@ -323,6 +323,7 @@ static int meson_sar_adc_wait_busy_clear(struct iio_dev *indio_dev)
> {
> struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
> int regval, timeout = 10000;
> + int ret;
why not add "ret" to the variables in the line above?
so this could be shortened to (which is also consistent with the
coding style in meson_saradc):
int ret, regval, timeout = 10000;

> @@ -506,7 +514,10 @@ static int meson_sar_adc_lock(struct iio_dev *indio_dev)
> */
> do {
> udelay(1);
> - regmap_read(priv->regmap, MESON_SAR_ADC_DELAY, &val);
> + ret = regmap_read(priv->regmap,
> + MESON_SAR_ADC_DELAY, &val);
> + if (ret)
> + return ret;
this is a big problem because we're returning with &indio_dev->mlock held
see the "timeout < 0" block below

> @@ -771,7 +782,7 @@ static int meson_sar_adc_init(struct iio_dev *indio_dev)
> {
> struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
> int regval, i, ret;
> -
> + int ret;
this removes an empty line between the variable declarations and the
first code (comment)
also "ret" is already defined in the line before
(I haven't compile-tested this myself yet but I'm surprised that this
doesn't give an error or at least a warning)

> @@ -1013,8 +1027,12 @@ static irqreturn_t meson_sar_adc_irq(int irq, void *data)
> struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
> unsigned int cnt, threshold;
> u32 regval;
> + int ret;
> +
> + ret = regmap_read(priv->regmap, MESON_SAR_ADC_REG0, &regval);
> + if (ret)
> + return ret;
this function doesn't return "int" but irqreturn_t
the only allowed values are: [0]


Martin


[0] https://elixir.bootlin.com/linux/v5.3/source/include/linux/irqreturn.h#L11