| Message ID | 20200312133244.9564-1-wsa@the-dreams.de (mailing list archive) |
|---|---|
| State | RFC, archived |
| Headers | show |
| Series | [RFC] i2c: acpi: put device when verifying client fails | expand |
On Thu, Mar 12, 2020 at 2:32 PM Wolfram Sang <wsa@the-dreams.de> wrote: > From: Wolfram Sang <wsa+renesas@sang-engineering.com> > > i2c_verify_client() can fail, so we need to put the device when that > happens. > > Fixes: 525e6fabeae2 ("i2c / ACPI: add support for ACPI reconfigure notifications") > Reported-by: Geert Uytterhoeven <geert+renesas@glider.be> > Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be> Gr{oetje,eeting}s, Geert
On Thu, Mar 12, 2020 at 02:32:44PM +0100, Wolfram Sang wrote: > From: Wolfram Sang <wsa+renesas@sang-engineering.com> > > i2c_verify_client() can fail, so we need to put the device when that > happens. NAK, this will do double put and messing up with reference counters. Besides the fact, that device may disappear after looking up which leads us to even more problems. See how i2c_acpi_find_client_by_adev() is used in callers. > > Fixes: 525e6fabeae2 ("i2c / ACPI: add support for ACPI reconfigure notifications") > Reported-by: Geert Uytterhoeven <geert+renesas@glider.be> > Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> > --- > > RFC because I don't know if it can be that the returned dev is not an > i2c_client. Yet, since it can happen theoretically, I think we should > have the checks. > > drivers/i2c/i2c-core-acpi.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/drivers/i2c/i2c-core-acpi.c b/drivers/i2c/i2c-core-acpi.c > index 8f3dbc97a057..8b0ff780919b 100644 > --- a/drivers/i2c/i2c-core-acpi.c > +++ b/drivers/i2c/i2c-core-acpi.c > @@ -394,9 +394,17 @@ EXPORT_SYMBOL_GPL(i2c_acpi_find_adapter_by_handle); > static struct i2c_client *i2c_acpi_find_client_by_adev(struct acpi_device *adev) > { > struct device *dev; > + struct i2c_client *client; > > dev = bus_find_device_by_acpi_dev(&i2c_bus_type, adev); > - return dev ? i2c_verify_client(dev) : NULL; > + if (!dev) > + return NULL; > + > + client = i2c_verify_client(dev); > + if (!client) > + put_device(dev); > + > + return client; > } > > static int i2c_acpi_notify(struct notifier_block *nb, unsigned long value, > -- > 2.20.1 >
On Thu, Mar 12, 2020 at 04:47:39PM +0200, Andy Shevchenko wrote: > On Thu, Mar 12, 2020 at 02:32:44PM +0100, Wolfram Sang wrote: > > From: Wolfram Sang <wsa+renesas@sang-engineering.com> > > > > i2c_verify_client() can fail, so we need to put the device when that > > happens. > > NAK, this will do double put and messing up with reference counters. > Besides the fact, that device may disappear after looking up which leads us to > even more problems. > > See how i2c_acpi_find_client_by_adev() is used in callers. Perhaps proper "fix" is to add the explanation to a comment in the code to prevent false positive reports in the future?
On Thu, Mar 12, 2020 at 04:49:08PM +0200, Andy Shevchenko wrote: > On Thu, Mar 12, 2020 at 04:47:39PM +0200, Andy Shevchenko wrote: > > On Thu, Mar 12, 2020 at 02:32:44PM +0100, Wolfram Sang wrote: > > > From: Wolfram Sang <wsa+renesas@sang-engineering.com> > > > > > > i2c_verify_client() can fail, so we need to put the device when that > > > happens. > > > > NAK, this will do double put and messing up with reference counters. > > Besides the fact, that device may disappear after looking up which leads us to > > even more problems. > > > > See how i2c_acpi_find_client_by_adev() is used in callers. > > Perhaps proper "fix" is to add the explanation to a comment in the code to > prevent false positive reports in the future? Ah, sorry, I need to read it more carefully...
On Thu, Mar 12, 2020 at 02:32:44PM +0100, Wolfram Sang wrote: > From: Wolfram Sang <wsa+renesas@sang-engineering.com> > > i2c_verify_client() can fail, so we need to put the device when that > happens. I hope it's not a CoVID-19 makes me mistakenly commented in the first place. :-) So, theoretically below is possible, but practically it's doubtful. The I2CSerialBusV2() ACPI resource can be present solely in I²C slave device nodes according to the specification. However, we might have two possible cases a) screwed up ACPI table; b) I²C master which in turn is I²C slave. While a) has been so far unseen, b) case sounds like plasible for I²C muxes IIUC. So, I agree with the patch, and sorry for the first reaction. Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> > Fixes: 525e6fabeae2 ("i2c / ACPI: add support for ACPI reconfigure notifications") > Reported-by: Geert Uytterhoeven <geert+renesas@glider.be> > Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> > --- > > RFC because I don't know if it can be that the returned dev is not an > i2c_client. Yet, since it can happen theoretically, I think we should > have the checks. > > drivers/i2c/i2c-core-acpi.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/drivers/i2c/i2c-core-acpi.c b/drivers/i2c/i2c-core-acpi.c > index 8f3dbc97a057..8b0ff780919b 100644 > --- a/drivers/i2c/i2c-core-acpi.c > +++ b/drivers/i2c/i2c-core-acpi.c > @@ -394,9 +394,17 @@ EXPORT_SYMBOL_GPL(i2c_acpi_find_adapter_by_handle); > static struct i2c_client *i2c_acpi_find_client_by_adev(struct acpi_device *adev) > { > struct device *dev; > + struct i2c_client *client; > > dev = bus_find_device_by_acpi_dev(&i2c_bus_type, adev); > - return dev ? i2c_verify_client(dev) : NULL; > + if (!dev) > + return NULL; > + > + client = i2c_verify_client(dev); > + if (!client) > + put_device(dev); > + > + return client; > } > > static int i2c_acpi_notify(struct notifier_block *nb, unsigned long value, > -- > 2.20.1 >
On Thu, Mar 12, 2020 at 02:32:44PM +0100, Wolfram Sang wrote: > From: Wolfram Sang <wsa+renesas@sang-engineering.com> > > i2c_verify_client() can fail, so we need to put the device when that > happens. > > Fixes: 525e6fabeae2 ("i2c / ACPI: add support for ACPI reconfigure notifications") > Reported-by: Geert Uytterhoeven <geert+renesas@glider.be> > Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> > --- > > RFC because I don't know if it can be that the returned dev is not an > i2c_client. Yet, since it can happen theoretically, I think we should > have the checks. I agree, Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
On Thu, Mar 12, 2020 at 02:32:44PM +0100, Wolfram Sang wrote: > From: Wolfram Sang <wsa+renesas@sang-engineering.com> > > i2c_verify_client() can fail, so we need to put the device when that > happens. > > Fixes: 525e6fabeae2 ("i2c / ACPI: add support for ACPI reconfigure notifications") > Reported-by: Geert Uytterhoeven <geert+renesas@glider.be> > Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> Applied to for-current, thanks!
diff --git a/drivers/i2c/i2c-core-acpi.c b/drivers/i2c/i2c-core-acpi.c index 8f3dbc97a057..8b0ff780919b 100644 --- a/drivers/i2c/i2c-core-acpi.c +++ b/drivers/i2c/i2c-core-acpi.c @@ -394,9 +394,17 @@ EXPORT_SYMBOL_GPL(i2c_acpi_find_adapter_by_handle); static struct i2c_client *i2c_acpi_find_client_by_adev(struct acpi_device *adev) { struct device *dev; + struct i2c_client *client; dev = bus_find_device_by_acpi_dev(&i2c_bus_type, adev); - return dev ? i2c_verify_client(dev) : NULL; + if (!dev) + return NULL; + + client = i2c_verify_client(dev); + if (!client) + put_device(dev); + + return client; } static int i2c_acpi_notify(struct notifier_block *nb, unsigned long value,