Re: [PATCH 1/2] hwmon: (dell-smm) Simplify ioctl handler

[Armin Wolf]

Am 23.11.21 um 17:13 schrieb Pali Rohár:

> On Saturday 20 November 2021 18:03:18 Armin Wolf wrote:
> > The second switch-case has no real purpose:
> >
> > - for I8K_BIOS_VERSION, val does not represent a return value,
> >    making the check for error values unnecessary.
> > - for I8K_MACHINE_ID, val remains zero, so the error check is
> >    unnecessary too.
> >
> > Remove the switch-case and move the calls to copy_to_user()
> > into the first switch-case for I8K_BIOS_VERSION/_MACHINE_ID.
> > Omit buff[] since data->machineid already contains the string
> s/->machineid/->bios_machineid/
>
> > with the necessary zero padding.
> data is allocated by devm_kzalloc() so data->bios_machineid is really
> zero padded.
>
> > Tested on a Dell Inspiron 3505.
> >
> > Signed-off-by: Armin Wolf <W_Armin@xxxxxx>
> > ---
> >   drivers/hwmon/dell-smm-hwmon.c | 30 +++++++++---------------------
> >   1 file changed, 9 insertions(+), 21 deletions(-)
> >
> > diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
> > index 5596c211f38d..b5d1703faa62 100644
> > --- a/drivers/hwmon/dell-smm-hwmon.c
> > +++ b/drivers/hwmon/dell-smm-hwmon.c
> > @@ -454,7 +454,6 @@ i8k_ioctl_unlocked(struct file *fp, struct dell_smm_data *data, unsigned int cmd
> >   {
> >   	int val = 0;
> >   	int speed, err;
> > -	unsigned char buff[16];
> >   	int __user *argp = (int __user *)arg;
> >
> >   	if (!argp)
> > @@ -468,15 +467,19 @@ i8k_ioctl_unlocked(struct file *fp, struct dell_smm_data *data, unsigned int cmd
> >
> >   		val = (data->bios_version[0] << 16) |
> >   				(data->bios_version[1] << 8) | data->bios_version[2];
> > -		break;
> >
> > +		if (copy_to_user(argp, &val, 4))
> > +			return -EFAULT;
> > +
> > +		return 0;
> >   	case I8K_MACHINE_ID:
> >   		if (restricted && !capable(CAP_SYS_ADMIN))
> >   			return -EPERM;
> >
> > -		strscpy_pad(buff, data->bios_machineid, sizeof(buff));
> > -		break;
> > +		if (copy_to_user(argp, data->bios_machineid, 16))
> What about usage of sizeof(data->bios_machineid) instead of hardcoded
> constant 16? And maybe same for constant 4?

For the string yes, but maybe i should change the int to an u32?

> > +			return -EFAULT;
> >
> > +		return 0;
> >   	case I8K_FN_STATUS:
> >   		val = i8k_get_fn_status();
> >   		break;
> > @@ -527,23 +530,8 @@ i8k_ioctl_unlocked(struct file *fp, struct dell_smm_data *data, unsigned int cmd
> >   	if (val < 0)
> >   		return val;
> >
> > -	switch (cmd) {
> > -	case I8K_BIOS_VERSION:
> > -		if (copy_to_user(argp, &val, 4))
> > -			return -EFAULT;
> > -
> > -		break;
> > -	case I8K_MACHINE_ID:
> > -		if (copy_to_user(argp, buff, 16))
> > -			return -EFAULT;
> > -
> > -		break;
> > -	default:
> > -		if (copy_to_user(argp, &val, sizeof(int)))
> > -			return -EFAULT;
> > -
> > -		break;
> > -	}
> > +	if (copy_to_user(argp, &val, sizeof(int)))
> > +		return -EFAULT;
> >
> >   	return 0;
> >   }
> > --
> > 2.30.2