[PATCH] platform/x86: huawei-wmi: Fix misuse of strcmp() function

[PATCH] platform/x86: huawei-wmi: Fix misuse of strcmp() function

[Gustavo A. R. Silva]

Comparing the result of strcmp directly with 1 may cause it to be
misinterpreted. Note that strcmp may return an integer besides -1,
0, or 1.

Fix this by returning -ENODEV only when strcmp() returns a value
other than 0.

Addresses-Coverity-ID: 1487035 ("Misuse of memcmp-style function")
Fixes: b7527d0f4502 ("platform/x86: huawei-wmi: Add battery charging thresholds")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 drivers/platform/x86/huawei-wmi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/platform/x86/huawei-wmi.c b/drivers/platform/x86/huawei-wmi.c
index 6720f78c60c2..b43f76acbfea 100644
--- a/drivers/platform/x86/huawei-wmi.c
+++ b/drivers/platform/x86/huawei-wmi.c
@@ -470,7 +470,7 @@ static DEVICE_ATTR_RW(charge_control_thresholds);
 static int huawei_wmi_battery_add(struct power_supply *battery)
 {
 	/* Huawei laptops come with one battery only */
-	if (strcmp(battery->desc->name, "BAT") != 1)
+	if (strcmp(battery->desc->name, "BAT"))
 		return -ENODEV;
 
 	device_create_file(&battery->dev, &dev_attr_charge_control_start_threshold);
-- 
2.23.0

Re: [PATCH] platform/x86: huawei-wmi: Fix misuse of strcmp() function

[ayman.bagabas]

Hi Gustavo,

On Tue, 2019-10-15 at 13:25 -0500, Gustavo A. R. Silva wrote:
> Comparing the result of strcmp directly with 1 may cause it to be
> misinterpreted. Note that strcmp may return an integer besides -1,
> 0, or 1.
> 
> Fix this by returning -ENODEV only when strcmp() returns a value
> other than 0.
> 
> Addresses-Coverity-ID: 1487035 ("Misuse of memcmp-style function")
> Fixes: b7527d0f4502 ("platform/x86: huawei-wmi: Add battery charging
> thresholds")
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
>  drivers/platform/x86/huawei-wmi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/x86/huawei-wmi.c
> b/drivers/platform/x86/huawei-wmi.c
> index 6720f78c60c2..b43f76acbfea 100644
> --- a/drivers/platform/x86/huawei-wmi.c
> +++ b/drivers/platform/x86/huawei-wmi.c
> @@ -470,7 +470,7 @@ static DEVICE_ATTR_RW(charge_control_thresholds);
>  static int huawei_wmi_battery_add(struct power_supply *battery)
>  {
>  	/* Huawei laptops come with one battery only */
> -	if (strcmp(battery->desc->name, "BAT") != 1)

Note we don't have a battery number in BATx, strcmp would return 1 if
battery->desc->name is "BAT0" or any one digit. This is a desired
behavior where some Huawei laptops identify the first battery as "BAT1"
and this would match if name is greater than "BAT" by one digit.

Maybe strcmp(battery->desc->name, "BAT") < 0 is a better way to go.

> +	if (strcmp(battery->desc->name, "BAT"))
>  		return -ENODEV;

Now this would always return ENODEV.

Thank you,
Ayman

>  
>  	device_create_file(&battery->dev,
> &dev_attr_charge_control_start_threshold);

Re: [PATCH] platform/x86: huawei-wmi: Fix misuse of strcmp() function

[Gustavo A. R. Silva]

Hi Ayman,

On 10/15/19 14:08, ayman.bagabas@gmail.com wrote:

>>  	/* Huawei laptops come with one battery only */
>> -	if (strcmp(battery->desc->name, "BAT") != 1)
> 
> Note we don't have a battery number in BATx, strcmp would return 1 if
> battery->desc->name is "BAT0" or any one digit. This is a desired
> behavior where some Huawei laptops identify the first battery as "BAT1"
> and this would match if name is greater than "BAT" by one digit.
> 

Great to know this is not a bug. I don't think there is any
other instance in the whole codebase like this one: strcmp(...) != 1
So, that's an odd thing to see...  Maybe you can consider adding
the whole description above as a code comment? :)

> Maybe strcmp(battery->desc->name, "BAT") < 0 is a better way to go.
> 

Yeah; this is bit more specific.

Thanks!
--
Gustavo