We need to call hwmon_device_unregister() if an error is detected after
sucessfully register hwmon device.
Signed-off-by: Axel Lin <[email protected]>
---
drivers/hwmon/ads7871.c | 4 +++-
1 files changed, 3 insertions(+), 1 deletions(-)
diff --git a/drivers/hwmon/ads7871.c b/drivers/hwmon/ads7871.c
index b300a20..303db92 100644
--- a/drivers/hwmon/ads7871.c
+++ b/drivers/hwmon/ads7871.c
@@ -201,11 +201,13 @@ static int __devinit ads7871_probe(struct spi_device *spi)
we need to make sure we really have a chip*/
if (val != ret) {
err = -ENODEV;
- goto error_remove;
+ goto error_unregister;
}
return 0;
+error_unregister:
+ hwmon_device_unregister(pdata->hwmon_dev);
error_remove:
sysfs_remove_group(&spi->dev.kobj, &ads7871_group);
error_free:
--
1.7.2
Hi Alex,
On Mon, 16 Aug 2010 09:31:17 +0800, Axel Lin wrote:
> We need to call hwmon_device_unregister() if an error is detected after
> sucessfully register hwmon device.
>
> Signed-off-by: Axel Lin <[email protected]>
> ---
> drivers/hwmon/ads7871.c | 4 +++-
> 1 files changed, 3 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/hwmon/ads7871.c b/drivers/hwmon/ads7871.c
> index b300a20..303db92 100644
> --- a/drivers/hwmon/ads7871.c
> +++ b/drivers/hwmon/ads7871.c
> @@ -201,11 +201,13 @@ static int __devinit ads7871_probe(struct spi_device *spi)
> we need to make sure we really have a chip*/
> if (val != ret) {
> err = -ENODEV;
> - goto error_remove;
> + goto error_unregister;
> }
>
> return 0;
>
> +error_unregister:
> + hwmon_device_unregister(pdata->hwmon_dev);
> error_remove:
> sysfs_remove_group(&spi->dev.kobj, &ads7871_group);
> error_free:
The bug is real, but I don't think the fix is correct. You should never
have to unregister the hwmon device in the error path, because you
should ensure the hardware is there and working _before_ you register
the hwmon device.
User-space could watch for hwmon devices being added or removed, and
you don't want to trigger such events for a device which isn't going to
work.
So I would suggest reworking the order in which things are done,
leaving hwmon_device_register() at the end of the function. This won't
only fix the error path, this will also close a race window, as for the
moment, the device is exposed to user-space _before_ it it properly
initialized, which is wrong.
Please send an updated patch and I'll be happy to apply it.
--
Jean Delvare
On Tue, Aug 17, 2010 at 4:07 AM, Jean Delvare <[email protected]> wrote:
> Hi Alex,
>
> On Mon, 16 Aug 2010 09:31:17 +0800, Axel Lin wrote:
>> We need to call hwmon_device_unregister() if an error is detected after
>> sucessfully register hwmon device.
>>
>> Signed-off-by: Axel Lin <[email protected]>
>> ---
>> ?drivers/hwmon/ads7871.c | ? ?4 +++-
>> ?1 files changed, 3 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/hwmon/ads7871.c b/drivers/hwmon/ads7871.c
>> index b300a20..303db92 100644
>> --- a/drivers/hwmon/ads7871.c
>> +++ b/drivers/hwmon/ads7871.c
>> @@ -201,11 +201,13 @@ static int __devinit ads7871_probe(struct spi_device *spi)
>> ? ? ? we need to make sure we really have a chip*/
>> ? ? ? if (val != ret) {
>> ? ? ? ? ? ? ? err = -ENODEV;
>> - ? ? ? ? ? ? goto error_remove;
>> + ? ? ? ? ? ? goto error_unregister;
>> ? ? ? }
>>
>> ? ? ? return 0;
>>
>> +error_unregister:
>> + ? ? hwmon_device_unregister(pdata->hwmon_dev);
>> ?error_remove:
>> ? ? ? sysfs_remove_group(&spi->dev.kobj, &ads7871_group);
>> ?error_free:
>
> The bug is real, but I don't think the fix is correct. You should never
> have to unregister the hwmon device in the error path, because you
> should ensure the hardware is there and working _before_ you register
> the hwmon device.
>
> User-space could watch for hwmon devices being added or removed, and
> you don't want to trigger such events for a device which isn't going to
> work.
>
> So I would suggest reworking the order in which things are done,
> leaving hwmon_device_register() at the end of the function. This won't
> only fix the error path, this will also close a race window, as for the
> moment, the device is exposed to user-space _before_ it it properly
> initialized, which is wrong.
>
> Please send an updated patch and I'll be happy to apply it.
>
> --
> Jean Delvare
>
Should the kzalloc, sysfs_create_group and hwmon_device_register all
stay in the same order just following the register check? I can send a
patch for that.
thanks,
Paul
On Tue, 17 Aug 2010 08:15:59 -0700, Paul Thomas wrote:
> On Tue, Aug 17, 2010 at 4:07 AM, Jean Delvare <[email protected]> wrote:
> > Hi Alex,
> >
> > On Mon, 16 Aug 2010 09:31:17 +0800, Axel Lin wrote:
> >> We need to call hwmon_device_unregister() if an error is detected after
> >> sucessfully register hwmon device.
> >>
> >> Signed-off-by: Axel Lin <[email protected]>
> >> ---
> >> drivers/hwmon/ads7871.c | 4 +++-
> >> 1 files changed, 3 insertions(+), 1 deletions(-)
> >>
> >> diff --git a/drivers/hwmon/ads7871.c b/drivers/hwmon/ads7871.c
> >> index b300a20..303db92 100644
> >> --- a/drivers/hwmon/ads7871.c
> >> +++ b/drivers/hwmon/ads7871.c
> >> @@ -201,11 +201,13 @@ static int __devinit ads7871_probe(struct spi_device *spi)
> >> we need to make sure we really have a chip*/
> >> if (val != ret) {
> >> err = -ENODEV;
> >> - goto error_remove;
> >> + goto error_unregister;
> >> }
> >>
> >> return 0;
> >>
> >> +error_unregister:
> >> + hwmon_device_unregister(pdata->hwmon_dev);
> >> error_remove:
> >> sysfs_remove_group(&spi->dev.kobj, &ads7871_group);
> >> error_free:
> >
> > The bug is real, but I don't think the fix is correct. You should never
> > have to unregister the hwmon device in the error path, because you
> > should ensure the hardware is there and working _before_ you register
> > the hwmon device.
> >
> > User-space could watch for hwmon devices being added or removed, and
> > you don't want to trigger such events for a device which isn't going to
> > work.
> >
> > So I would suggest reworking the order in which things are done,
> > leaving hwmon_device_register() at the end of the function. This won't
> > only fix the error path, this will also close a race window, as for the
> > moment, the device is exposed to user-space _before_ it it properly
> > initialized, which is wrong.
> >
> > Please send an updated patch and I'll be happy to apply it.
> >
> > --
> > Jean Delvare
> >
>
> Should the kzalloc, sysfs_create_group and hwmon_device_register all
> stay in the same order just following the register check? I can send a
> patch for that.
Axel already sent an updated patch, so it's all OK.
--
Jean Delvare