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SubjectRe: [PATCH] [v2] staging: iio: ad5933: avoid uninitialized variable in error case
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On 24/10/16 16:22, Arnd Bergmann wrote:
> The ad5933_i2c_read function returns an error code to indicate
> whether it could read data or not. However ad5933_work() ignores
> this return code and just accesses the data unconditionally,
> which gets detected by gcc as a possible bug:
>
> drivers/staging/iio/impedance-analyzer/ad5933.c: In function 'ad5933_work':
> drivers/staging/iio/impedance-analyzer/ad5933.c:649:16: warning: 'status' may be used uninitialized in this function [-Wmaybe-uninitialized]
>
> This adds minimal error handling so we only evaluate the
> data if it was correctly read.
>
> Link: https://patchwork.kernel.org/patch/8110281/
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Looks good to me.

Lars?


> ---
> v2: handle failure for both affected reads instead of just the one
> we get a warning for
> v2: do not retry on failure to avoid looping in case of permanent
> errors
> ---
> drivers/staging/iio/impedance-analyzer/ad5933.c | 17 ++++++++++-------
> 1 file changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/staging/iio/impedance-analyzer/ad5933.c b/drivers/staging/iio/impedance-analyzer/ad5933.c
> index 5eecf1cb1028..3892a7470410 100644
> --- a/drivers/staging/iio/impedance-analyzer/ad5933.c
> +++ b/drivers/staging/iio/impedance-analyzer/ad5933.c
> @@ -655,6 +655,7 @@ static void ad5933_work(struct work_struct *work)
> __be16 buf[2];
> int val[2];
> unsigned char status;
> + int ret;
>
> mutex_lock(&indio_dev->mlock);
> if (st->state == AD5933_CTRL_INIT_START_FREQ) {
> @@ -662,19 +663,22 @@ static void ad5933_work(struct work_struct *work)
> ad5933_cmd(st, AD5933_CTRL_START_SWEEP);
> st->state = AD5933_CTRL_START_SWEEP;
> schedule_delayed_work(&st->work, st->poll_time_jiffies);
> - mutex_unlock(&indio_dev->mlock);
> - return;
> + goto out;
> }
>
> - ad5933_i2c_read(st->client, AD5933_REG_STATUS, 1, &status);
> + ret = ad5933_i2c_read(st->client, AD5933_REG_STATUS, 1, &status);
> + if (ret)
> + goto out;
>
> if (status & AD5933_STAT_DATA_VALID) {
> int scan_count = bitmap_weight(indio_dev->active_scan_mask,
> indio_dev->masklength);
> - ad5933_i2c_read(st->client,
> + ret = ad5933_i2c_read(st->client,
> test_bit(1, indio_dev->active_scan_mask) ?
> AD5933_REG_REAL_DATA : AD5933_REG_IMAG_DATA,
> scan_count * 2, (u8 *)buf);
> + if (ret)
> + goto out;
>
> if (scan_count == 2) {
> val[0] = be16_to_cpu(buf[0]);
> @@ -686,8 +690,7 @@ static void ad5933_work(struct work_struct *work)
> } else {
> /* no data available - try again later */
> schedule_delayed_work(&st->work, st->poll_time_jiffies);
> - mutex_unlock(&indio_dev->mlock);
> - return;
> + goto out;
> }
>
> if (status & AD5933_STAT_SWEEP_DONE) {
> @@ -700,7 +703,7 @@ static void ad5933_work(struct work_struct *work)
> ad5933_cmd(st, AD5933_CTRL_INC_FREQ);
> schedule_delayed_work(&st->work, st->poll_time_jiffies);
> }
> -
> +out:
> mutex_unlock(&indio_dev->mlock);
> }
>
>

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