Messages in this thread | | | Date | Tue, 17 Aug 2010 08:15:59 -0700 | Subject | Re: [PATCH] hwmon: (ads7871) Fix ads7871_probe error path | From | Paul Thomas <> |
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On Tue, Aug 17, 2010 at 4:07 AM, Jean Delvare <khali@linux-fr.org> 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 <axel.lin@gmail.com> >> --- >> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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