2020-07-22 13:42:46

by Tom Rix

Subject: [PATCH] media: dvb-frontends/cxd2099: report errors

From: Tom Rix <[email protected]>

Clang static analysis reports this error

drivers/media/dvb-frontends/cxd2099.c:420:2: warning: Undefined
or garbage value returned to caller
return val;
^~~~~~~~~~

In read_cam_control, the call to read_io can fail.
When it fails val is not set.

The failure status should be returned to the caller,
not the unset val.

Similar problem with read_attribute_mem

Fixes: 0f0b270f905b ("[media] ngene: CXD2099AR Common Interface driver")

Signed-off-by: Tom Rix <[email protected]>
---
drivers/media/dvb-frontends/cxd2099.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/media/dvb-frontends/cxd2099.c b/drivers/media/dvb-frontends/cxd2099.c
index f88b5355493e..9dfaf18fc4b4 100644
--- a/drivers/media/dvb-frontends/cxd2099.c
+++ b/drivers/media/dvb-frontends/cxd2099.c
@@ -387,12 +387,15 @@ static int read_attribute_mem(struct dvb_ca_en50221 *ca,
{
struct cxd *ci = ca->data;
u8 val;
+ int ret;

mutex_lock(&ci->lock);
set_mode(ci, 1);
- read_pccard(ci, address, &val, 1);
+ ret = read_pccard(ci, address, &val, 1);
+ if (!ret)
+ ret = val;
mutex_unlock(&ci->lock);
- return val;
+ return ret;
}

static int write_attribute_mem(struct dvb_ca_en50221 *ca, int slot,
@@ -412,12 +415,15 @@ static int read_cam_control(struct dvb_ca_en50221 *ca,
{
struct cxd *ci = ca->data;
unsigned int val;
+ int ret;

mutex_lock(&ci->lock);
set_mode(ci, 0);
- read_io(ci, address, &val);
+ ret = read_io(ci, address, &val);
+ if (!ret)
+ ret = val;
mutex_unlock(&ci->lock);
- return val;
+ return ret;
}

static int write_cam_control(struct dvb_ca_en50221 *ca, int slot,
--
2.18.1

2020-09-03 14:43:39

by Tom Rix

Subject: Re: [PATCH] media: dvb-frontends/cxd2099: report errors

On 9/3/20 7:13 AM, Mauro Carvalho Chehab wrote:
> Em Wed, 22 Jul 2020 06:41:26 -0700
> [email protected] escreveu:
>
>> From: Tom Rix <[email protected]>
>>
>> Clang static analysis reports this error
>>
>> drivers/media/dvb-frontends/cxd2099.c:420:2: warning: Undefined
>> or garbage value returned to caller
>> return val;
>> ^~~~~~~~~~
>>
>> In read_cam_control, the call to read_io can fail.
>> When it fails val is not set.
>>
>> The failure status should be returned to the caller,
>> not the unset val.
>>
>> Similar problem with read_attribute_mem
>>
>> Fixes: 0f0b270f905b ("[media] ngene: CXD2099AR Common Interface driver")
>>
>> Signed-off-by: Tom Rix <[email protected]>
>> ---
>> drivers/media/dvb-frontends/cxd2099.c | 14 ++++++++++----
>> 1 file changed, 10 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/media/dvb-frontends/cxd2099.c b/drivers/media/dvb-frontends/cxd2099.c
>> index f88b5355493e..9dfaf18fc4b4 100644
>> --- a/drivers/media/dvb-frontends/cxd2099.c
>> +++ b/drivers/media/dvb-frontends/cxd2099.c
>> @@ -387,12 +387,15 @@ static int read_attribute_mem(struct dvb_ca_en50221 *ca,
>> {
>> struct cxd *ci = ca->data;
>> u8 val;
>> + int ret;
>>
>> mutex_lock(&ci->lock);
>> set_mode(ci, 1);
>> - read_pccard(ci, address, &val, 1);
>> + ret = read_pccard(ci, address, &val, 1);
>> + if (!ret)
>> + ret = val;
>> mutex_unlock(&ci->lock);
>> - return val;
>> + return ret;
>> }
>>
>> static int write_attribute_mem(struct dvb_ca_en50221 *ca, int slot,
>> @@ -412,12 +415,15 @@ static int read_cam_control(struct dvb_ca_en50221 *ca,
>> {
>> struct cxd *ci = ca->data;
>> unsigned int val;
>> + int ret;
>>
>> mutex_lock(&ci->lock);
>> set_mode(ci, 0);
>> - read_io(ci, address, &val);
>> + ret = read_io(ci, address, &val);
>> + if (!ret)
>> + ret = val;
>> mutex_unlock(&ci->lock);
>> - return val;
>> + return ret;
>> }
>>
>> static int write_cam_control(struct dvb_ca_en50221 *ca, int slot,
> Hmm... Had you test this one on a real hardware? It is not
> uncommon to have some DVB devices that would fail reading
> when the firmware is on cold state.
>
> Without testing a patch like that at a real hardware, there's
> no way to know if this is intentional or if the original
> developer forgot to add a check for the error.

No, I do not have hw.  I understand your concerns, it is ok if you want to drop this patch, else i'll beef up the warnings.

Tom

>
> So, at most, it could print some warning message for
> non-zero return codes.
>
>
> Thanks,
> Mauro
>

2020-09-03 14:53:24

by Mauro Carvalho Chehab

Subject: Re: [PATCH] media: dvb-frontends/cxd2099: report errors

Em Wed, 22 Jul 2020 06:41:26 -0700
[email protected] escreveu:

> From: Tom Rix <[email protected]>
>
> Clang static analysis reports this error
>
> drivers/media/dvb-frontends/cxd2099.c:420:2: warning: Undefined
> or garbage value returned to caller
> return val;
> ^~~~~~~~~~
>
> In read_cam_control, the call to read_io can fail.
> When it fails val is not set.
>
> The failure status should be returned to the caller,
> not the unset val.
>
> Similar problem with read_attribute_mem
>
> Fixes: 0f0b270f905b ("[media] ngene: CXD2099AR Common Interface driver")
>
> Signed-off-by: Tom Rix <[email protected]>
> ---
> drivers/media/dvb-frontends/cxd2099.c | 14 ++++++++++----
> 1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/media/dvb-frontends/cxd2099.c b/drivers/media/dvb-frontends/cxd2099.c
> index f88b5355493e..9dfaf18fc4b4 100644
> --- a/drivers/media/dvb-frontends/cxd2099.c
> +++ b/drivers/media/dvb-frontends/cxd2099.c
> @@ -387,12 +387,15 @@ static int read_attribute_mem(struct dvb_ca_en50221 *ca,
> {
> struct cxd *ci = ca->data;
> u8 val;
> + int ret;
>
> mutex_lock(&ci->lock);
> set_mode(ci, 1);
> - read_pccard(ci, address, &val, 1);
> + ret = read_pccard(ci, address, &val, 1);
> + if (!ret)
> + ret = val;
> mutex_unlock(&ci->lock);
> - return val;
> + return ret;
> }
>
> static int write_attribute_mem(struct dvb_ca_en50221 *ca, int slot,
> @@ -412,12 +415,15 @@ static int read_cam_control(struct dvb_ca_en50221 *ca,
> {
> struct cxd *ci = ca->data;
> unsigned int val;
> + int ret;
>
> mutex_lock(&ci->lock);
> set_mode(ci, 0);
> - read_io(ci, address, &val);
> + ret = read_io(ci, address, &val);
> + if (!ret)
> + ret = val;
> mutex_unlock(&ci->lock);
> - return val;
> + return ret;
> }
>
> static int write_cam_control(struct dvb_ca_en50221 *ca, int slot,

Hmm... Had you test this one on a real hardware? It is not
uncommon to have some DVB devices that would fail reading
when the firmware is on cold state.

Without testing a patch like that at a real hardware, there's
no way to know if this is intentional or if the original
developer forgot to add a check for the error.

So, at most, it could print some warning message for
non-zero return codes.


Thanks,
Mauro