* [PATCH] hwmon: (adt7470) Prevent divide by zero in adt7470_fan_write()
@ 2022-01-21 5:39 Dan Carpenter
2022-01-21 6:10 ` Guenter Roeck
0 siblings, 1 reply; 4+ messages in thread
From: Dan Carpenter @ 2022-01-21 5:39 UTC (permalink / raw)
To: Jean Delvare, Chris Packham; +Cc: Guenter Roeck, linux-hwmon, kernel-janitors
The "val" variable is controlled by the user and comes from
hwmon_attr_store(). The FAN_RPM_TO_PERIOD() macro divides by "val"
so a zero will crash the system. Check for that and return -EINVAL.
Fixes: fc958a61ff6d ("hwmon: (adt7470) Convert to devm_hwmon_device_register_with_info API")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
drivers/hwmon/adt7470.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/hwmon/adt7470.c b/drivers/hwmon/adt7470.c
index d519aca4a9d6..cd474584dc0b 100644
--- a/drivers/hwmon/adt7470.c
+++ b/drivers/hwmon/adt7470.c
@@ -662,6 +662,9 @@ static int adt7470_fan_write(struct device *dev, u32 attr, int channel, long val
struct adt7470_data *data = dev_get_drvdata(dev);
int err;
+ if (!val)
+ return -EINVAL;
+
val = FAN_RPM_TO_PERIOD(val);
val = clamp_val(val, 1, 65534);
--
2.20.1
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] hwmon: (adt7470) Prevent divide by zero in adt7470_fan_write()
2022-01-21 5:39 [PATCH] hwmon: (adt7470) Prevent divide by zero in adt7470_fan_write() Dan Carpenter
@ 2022-01-21 6:10 ` Guenter Roeck
2022-01-21 7:37 ` Dan Carpenter
0 siblings, 1 reply; 4+ messages in thread
From: Guenter Roeck @ 2022-01-21 6:10 UTC (permalink / raw)
To: Dan Carpenter, Jean Delvare, Chris Packham; +Cc: linux-hwmon, kernel-janitors
On 1/20/22 9:39 PM, Dan Carpenter wrote:
> The "val" variable is controlled by the user and comes from
> hwmon_attr_store(). The FAN_RPM_TO_PERIOD() macro divides by "val"
> so a zero will crash the system. Check for that and return -EINVAL.
>
> Fixes: fc958a61ff6d ("hwmon: (adt7470) Convert to devm_hwmon_device_register_with_info API")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> drivers/hwmon/adt7470.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/hwmon/adt7470.c b/drivers/hwmon/adt7470.c
> index d519aca4a9d6..cd474584dc0b 100644
> --- a/drivers/hwmon/adt7470.c
> +++ b/drivers/hwmon/adt7470.c
> @@ -662,6 +662,9 @@ static int adt7470_fan_write(struct device *dev, u32 attr, int channel, long val
> struct adt7470_data *data = dev_get_drvdata(dev);
> int err;
>
> + if (!val)
> + return -EINVAL;
> +
Technically that restores old (pre-fc958a61ff6d) behavior, but it is still bad:
Userspace can provide a value of -1 (or any other negative number), and it will
translate to 5400000 RPM. So it should either be
if (val <= 0)
return -EINVAL;
or
if (val <= 0)
val = 1;
Thanks,
Guenter
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] hwmon: (adt7470) Prevent divide by zero in adt7470_fan_write()
2022-01-21 6:10 ` Guenter Roeck
@ 2022-01-21 7:37 ` Dan Carpenter
2022-01-21 14:03 ` Guenter Roeck
0 siblings, 1 reply; 4+ messages in thread
From: Dan Carpenter @ 2022-01-21 7:37 UTC (permalink / raw)
To: Guenter Roeck; +Cc: Jean Delvare, Chris Packham, linux-hwmon, kernel-janitors
On Thu, Jan 20, 2022 at 10:10:45PM -0800, Guenter Roeck wrote:
> On 1/20/22 9:39 PM, Dan Carpenter wrote:
> > The "val" variable is controlled by the user and comes from
> > hwmon_attr_store(). The FAN_RPM_TO_PERIOD() macro divides by "val"
> > so a zero will crash the system. Check for that and return -EINVAL.
> >
> > Fixes: fc958a61ff6d ("hwmon: (adt7470) Convert to devm_hwmon_device_register_with_info API")
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > ---
> > drivers/hwmon/adt7470.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/hwmon/adt7470.c b/drivers/hwmon/adt7470.c
> > index d519aca4a9d6..cd474584dc0b 100644
> > --- a/drivers/hwmon/adt7470.c
> > +++ b/drivers/hwmon/adt7470.c
> > @@ -662,6 +662,9 @@ static int adt7470_fan_write(struct device *dev, u32 attr, int channel, long val
> > struct adt7470_data *data = dev_get_drvdata(dev);
> > int err;
> > + if (!val)
> > + return -EINVAL;
> > +
>
> Technically that restores old (pre-fc958a61ff6d) behavior, but it is still bad:
> Userspace can provide a value of -1 (or any other negative number), and it will
> translate to 5400000 RPM. So it should either be
>
> if (val <= 0)
> return -EINVAL;
>
> or
> if (val <= 0)
> val = 1;
There is a clamp() which does already turn invalid values into something
valid.
val = FAN_RPM_TO_PERIOD(val);
val = clamp_val(val, 1, 65534);
But I will make the <= 0 return -EINVAL change and resend.
regards,
dan carpenter
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] hwmon: (adt7470) Prevent divide by zero in adt7470_fan_write()
2022-01-21 7:37 ` Dan Carpenter
@ 2022-01-21 14:03 ` Guenter Roeck
0 siblings, 0 replies; 4+ messages in thread
From: Guenter Roeck @ 2022-01-21 14:03 UTC (permalink / raw)
To: Dan Carpenter; +Cc: Jean Delvare, Chris Packham, linux-hwmon, kernel-janitors
On 1/20/22 11:37 PM, Dan Carpenter wrote:
> On Thu, Jan 20, 2022 at 10:10:45PM -0800, Guenter Roeck wrote:
>> On 1/20/22 9:39 PM, Dan Carpenter wrote:
>>> The "val" variable is controlled by the user and comes from
>>> hwmon_attr_store(). The FAN_RPM_TO_PERIOD() macro divides by "val"
>>> so a zero will crash the system. Check for that and return -EINVAL.
>>>
>>> Fixes: fc958a61ff6d ("hwmon: (adt7470) Convert to devm_hwmon_device_register_with_info API")
>>> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>>> ---
>>> drivers/hwmon/adt7470.c | 3 +++
>>> 1 file changed, 3 insertions(+)
>>>
>>> diff --git a/drivers/hwmon/adt7470.c b/drivers/hwmon/adt7470.c
>>> index d519aca4a9d6..cd474584dc0b 100644
>>> --- a/drivers/hwmon/adt7470.c
>>> +++ b/drivers/hwmon/adt7470.c
>>> @@ -662,6 +662,9 @@ static int adt7470_fan_write(struct device *dev, u32 attr, int channel, long val
>>> struct adt7470_data *data = dev_get_drvdata(dev);
>>> int err;
>>> + if (!val)
>>> + return -EINVAL;
>>> +
>>
>> Technically that restores old (pre-fc958a61ff6d) behavior, but it is still bad:
>> Userspace can provide a value of -1 (or any other negative number), and it will
>> translate to 5400000 RPM. So it should either be
>>
>> if (val <= 0)
>> return -EINVAL;
>>
>> or
>> if (val <= 0)
>> val = 1;
>
> There is a clamp() which does already turn invalid values into something
> valid.
>
Yes, but
-1 -> -5400000 -> 1, which translates to 5400000 rpm.
This is in contrast to
1 -> 5400000 -> 65534
which translates to a more reasonable 82 rpm.
> val = FAN_RPM_TO_PERIOD(val);
> val = clamp_val(val, 1, 65534);
>
> But I will make the <= 0 return -EINVAL change and resend.
>
Thanks,
Guenter
^ permalink raw reply [flat|nested] 4+ messages in thread
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2022-01-21 5:39 [PATCH] hwmon: (adt7470) Prevent divide by zero in adt7470_fan_write() Dan Carpenter
2022-01-21 6:10 ` Guenter Roeck
2022-01-21 7:37 ` Dan Carpenter
2022-01-21 14:03 ` Guenter Roeck
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