* [PATCH] staging: iio: ad5933: avoid uninitialized variable in error case
@ 2016-01-25 15:50 Arnd Bergmann
2016-01-30 14:18 ` Jonathan Cameron
0 siblings, 1 reply; 3+ messages in thread
From: Arnd Bergmann @ 2016-01-25 15:50 UTC (permalink / raw)
To: linux-arm-kernel
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.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
drivers/staging/iio/impedance-analyzer/ad5933.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/staging/iio/impedance-analyzer/ad5933.c b/drivers/staging/iio/impedance-analyzer/ad5933.c
index 10c43dda0f5a..304bb464e478 100644
--- a/drivers/staging/iio/impedance-analyzer/ad5933.c
+++ b/drivers/staging/iio/impedance-analyzer/ad5933.c
@@ -647,6 +647,7 @@ 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) {
@@ -658,9 +659,9 @@ static void ad5933_work(struct work_struct *work)
return;
}
- ad5933_i2c_read(st->client, AD5933_REG_STATUS, 1, &status);
+ ret = ad5933_i2c_read(st->client, AD5933_REG_STATUS, 1, &status);
- if (status & AD5933_STAT_DATA_VALID) {
+ if (!ret && (status & AD5933_STAT_DATA_VALID)) {
int scan_count = bitmap_weight(indio_dev->active_scan_mask,
indio_dev->masklength);
ad5933_i2c_read(st->client,
--
2.7.0
^ permalink raw reply related [flat|nested] 3+ messages in thread* [PATCH] staging: iio: ad5933: avoid uninitialized variable in error case
2016-01-25 15:50 [PATCH] staging: iio: ad5933: avoid uninitialized variable in error case Arnd Bergmann
@ 2016-01-30 14:18 ` Jonathan Cameron
2016-01-30 15:06 ` Lars-Peter Clausen
0 siblings, 1 reply; 3+ messages in thread
From: Jonathan Cameron @ 2016-01-30 14:18 UTC (permalink / raw)
To: linux-arm-kernel
On 25/01/16 15:50, 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.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Hi Arnd,
Thanks for the patch. The handling in here is a little fiddly
by the look of things. Lars can you take a look at this when
you have a minute?
At a very high level, it doesn't make sense to fix this instance and
not the one in the context of the patch below.
See below...
> ---
> drivers/staging/iio/impedance-analyzer/ad5933.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/staging/iio/impedance-analyzer/ad5933.c b/drivers/staging/iio/impedance-analyzer/ad5933.c
> index 10c43dda0f5a..304bb464e478 100644
> --- a/drivers/staging/iio/impedance-analyzer/ad5933.c
> +++ b/drivers/staging/iio/impedance-analyzer/ad5933.c
> @@ -647,6 +647,7 @@ 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) {
> @@ -658,9 +659,9 @@ static void ad5933_work(struct work_struct *work)
> return;
> }
>
> - ad5933_i2c_read(st->client, AD5933_REG_STATUS, 1, &status);
> + ret = ad5933_i2c_read(st->client, AD5933_REG_STATUS, 1, &status);
>
> - if (status & AD5933_STAT_DATA_VALID) {
> + if (!ret && (status & AD5933_STAT_DATA_VALID)) {
The else is non trivial here as it assumes we will get the data later. If we
get such a failure, we probably want to drop out completely rather than paper
over the gaps..
> int scan_count = bitmap_weight(indio_dev->active_scan_mask,
> indio_dev->masklength);
Same issue on the next line - this results in known garbage data being spooled
out.
> ad5933_i2c_read(st->client,
>
^ permalink raw reply [flat|nested] 3+ messages in thread* [PATCH] staging: iio: ad5933: avoid uninitialized variable in error case
2016-01-30 14:18 ` Jonathan Cameron
@ 2016-01-30 15:06 ` Lars-Peter Clausen
0 siblings, 0 replies; 3+ messages in thread
From: Lars-Peter Clausen @ 2016-01-30 15:06 UTC (permalink / raw)
To: linux-arm-kernel
On 01/30/2016 03:18 PM, Jonathan Cameron wrote:
> On 25/01/16 15:50, 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.
>>
>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Hi Arnd,
>
> Thanks for the patch. The handling in here is a little fiddly
> by the look of things. Lars can you take a look at this when
> you have a minute?
>
> At a very high level, it doesn't make sense to fix this instance and
> not the one in the context of the patch below.
> See below...
>> ---
>> drivers/staging/iio/impedance-analyzer/ad5933.c | 5 +++--
>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/staging/iio/impedance-analyzer/ad5933.c b/drivers/staging/iio/impedance-analyzer/ad5933.c
>> index 10c43dda0f5a..304bb464e478 100644
>> --- a/drivers/staging/iio/impedance-analyzer/ad5933.c
>> +++ b/drivers/staging/iio/impedance-analyzer/ad5933.c
>> @@ -647,6 +647,7 @@ 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) {
>> @@ -658,9 +659,9 @@ static void ad5933_work(struct work_struct *work)
>> return;
>> }
>>
>> - ad5933_i2c_read(st->client, AD5933_REG_STATUS, 1, &status);
>> + ret = ad5933_i2c_read(st->client, AD5933_REG_STATUS, 1, &status);
>>
>> - if (status & AD5933_STAT_DATA_VALID) {
>> + if (!ret && (status & AD5933_STAT_DATA_VALID)) {
> The else is non trivial here as it assumes we will get the data later. If we
> get such a failure, we probably want to drop out completely rather than paper
> over the gaps..
I agree. Although we could argue that Arnd's approach allows to recover from
temporary failure. But then again we don't want to keep polling forever if
it's a permanent failure. I'd say the best thing for a quick fix is to just
error out and assume the error is permanent.
>> int scan_count = bitmap_weight(indio_dev->active_scan_mask,
>> indio_dev->masklength);
> Same issue on the next line - this results in known garbage data being spooled
> out.
Also agreed.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2016-01-25 15:50 [PATCH] staging: iio: ad5933: avoid uninitialized variable in error case Arnd Bergmann
2016-01-30 14:18 ` Jonathan Cameron
2016-01-30 15:06 ` Lars-Peter Clausen
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