Currently it's possible to iterate over the dangling pointer in case the device
suddenly disappears. This may happen becase callers put it at the end of a loop.
Instead, let's move that call inside acpi_dev_get_next_match_dev().
Fixes: 803abec64ef9 ("media: ipu3-cio2: Add cio2-bridge to ipu3-cio2 driver")
Fixes: bf263f64e804 ("media: ACPI / bus: Add acpi_dev_get_next_match_dev() and helper macro")
Cc: Daniel Scally <[email protected]>
Cc: Sakari Ailus <[email protected]>
Signed-off-by: Andy Shevchenko <[email protected]>
---
drivers/acpi/utils.c | 5 +----
drivers/media/pci/intel/ipu3/cio2-bridge.c | 8 +++-----
include/acpi/acpi_bus.h | 5 -----
3 files changed, 4 insertions(+), 14 deletions(-)
diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
index 3b54b8fd7396..ccfc484dbffd 100644
--- a/drivers/acpi/utils.c
+++ b/drivers/acpi/utils.c
@@ -846,10 +846,6 @@ EXPORT_SYMBOL(acpi_dev_present);
* Return the next match of ACPI device if another matching device was present
* at the moment of invocation, or NULL otherwise.
*
- * FIXME: The function does not tolerate the sudden disappearance of @adev, e.g.
- * in the case of a hotplug event. That said, the caller should ensure that
- * this will never happen.
- *
* The caller is responsible for invoking acpi_dev_put() on the returned device.
*
* See additional information in acpi_dev_present() as well.
@@ -866,6 +862,7 @@ acpi_dev_get_next_match_dev(struct acpi_device *adev, const char *hid, const cha
match.hrv = hrv;
dev = bus_find_device(&acpi_bus_type, start, &match, acpi_dev_match_cb);
+ acpi_dev_put(adev);
return dev ? to_acpi_device(dev) : NULL;
}
EXPORT_SYMBOL(acpi_dev_get_next_match_dev);
diff --git a/drivers/media/pci/intel/ipu3/cio2-bridge.c b/drivers/media/pci/intel/ipu3/cio2-bridge.c
index e8511787c1e4..477417261b6e 100644
--- a/drivers/media/pci/intel/ipu3/cio2-bridge.c
+++ b/drivers/media/pci/intel/ipu3/cio2-bridge.c
@@ -178,13 +178,11 @@ static int cio2_bridge_connect_sensor(const struct cio2_sensor_config *cfg,
if (bridge->n_sensors >= CIO2_NUM_PORTS) {
dev_err(&cio2->dev, "Exceeded available CIO2 ports\n");
- cio2_bridge_unregister_sensors(bridge);
ret = -EINVAL;
- goto err_out;
+ goto err_put_adev;
}
sensor = &bridge->sensors[bridge->n_sensors];
- sensor->adev = adev;
strscpy(sensor->name, cfg->hid, sizeof(sensor->name));
ret = cio2_bridge_read_acpi_buffer(adev, "SSDB",
@@ -214,6 +212,7 @@ static int cio2_bridge_connect_sensor(const struct cio2_sensor_config *cfg,
goto err_free_swnodes;
}
+ sensor->adev = acpi_dev_get(adev);
adev->fwnode.secondary = fwnode;
dev_info(&cio2->dev, "Found supported sensor %s\n",
@@ -227,8 +226,7 @@ static int cio2_bridge_connect_sensor(const struct cio2_sensor_config *cfg,
err_free_swnodes:
software_node_unregister_nodes(sensor->swnodes);
err_put_adev:
- acpi_dev_put(sensor->adev);
-err_out:
+ acpi_dev_put(adev);
return ret;
}
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index 3a82faac5767..bff6a11bb21f 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -698,11 +698,6 @@ acpi_dev_get_first_match_dev(const char *hid, const char *uid, s64 hrv);
* @hrv: Hardware Revision of the device, pass -1 to not check _HRV
*
* The caller is responsible for invoking acpi_dev_put() on the returned device.
- *
- * FIXME: Due to above requirement there is a window that may invalidate @adev
- * and next iteration will use a dangling pointer, e.g. in the case of a
- * hotplug event. That said, the caller should ensure that this will never
- * happen.
*/
#define for_each_acpi_dev_match(adev, hid, uid, hrv) \
for (adev = acpi_dev_get_first_match_dev(hid, uid, hrv); \
--
2.31.1
On Wed, May 19, 2021 at 11:19 PM Andy Shevchenko
<[email protected]> wrote:
>
> Currently it's possible to iterate over the dangling pointer in case the device
> suddenly disappears. This may happen becase callers put it at the end of a loop.
>
> Instead, let's move that call inside acpi_dev_get_next_match_dev().
Not really.
> Fixes: 803abec64ef9 ("media: ipu3-cio2: Add cio2-bridge to ipu3-cio2 driver")
> Fixes: bf263f64e804 ("media: ACPI / bus: Add acpi_dev_get_next_match_dev() and helper macro")
> Cc: Daniel Scally <[email protected]>
> Cc: Sakari Ailus <[email protected]>
> Signed-off-by: Andy Shevchenko <[email protected]>
> ---
> drivers/acpi/utils.c | 5 +----
> drivers/media/pci/intel/ipu3/cio2-bridge.c | 8 +++-----
> include/acpi/acpi_bus.h | 5 -----
> 3 files changed, 4 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
> index 3b54b8fd7396..ccfc484dbffd 100644
> --- a/drivers/acpi/utils.c
> +++ b/drivers/acpi/utils.c
> @@ -846,10 +846,6 @@ EXPORT_SYMBOL(acpi_dev_present);
> * Return the next match of ACPI device if another matching device was present
> * at the moment of invocation, or NULL otherwise.
> *
> - * FIXME: The function does not tolerate the sudden disappearance of @adev, e.g.
> - * in the case of a hotplug event. That said, the caller should ensure that
> - * this will never happen.
> - *
> * The caller is responsible for invoking acpi_dev_put() on the returned device.
> *
> * See additional information in acpi_dev_present() as well.
> @@ -866,6 +862,7 @@ acpi_dev_get_next_match_dev(struct acpi_device *adev, const char *hid, const cha
> match.hrv = hrv;
>
> dev = bus_find_device(&acpi_bus_type, start, &match, acpi_dev_match_cb);
> + acpi_dev_put(adev);
What's the point?
The caller may as well put it after this returns, can't it?
And what if the caller still wants to do something with adev after this returns?
> return dev ? to_acpi_device(dev) : NULL;
> }
> EXPORT_SYMBOL(acpi_dev_get_next_match_dev);
The original changelog is somewhat unclear. It should say that it is
required to reference-count the start-point device before passing it
to this function, but beyond that I don't see a bug here.
> diff --git a/drivers/media/pci/intel/ipu3/cio2-bridge.c b/drivers/media/pci/intel/ipu3/cio2-bridge.c
> index e8511787c1e4..477417261b6e 100644
> --- a/drivers/media/pci/intel/ipu3/cio2-bridge.c
> +++ b/drivers/media/pci/intel/ipu3/cio2-bridge.c
> @@ -178,13 +178,11 @@ static int cio2_bridge_connect_sensor(const struct cio2_sensor_config *cfg,
>
> if (bridge->n_sensors >= CIO2_NUM_PORTS) {
> dev_err(&cio2->dev, "Exceeded available CIO2 ports\n");
> - cio2_bridge_unregister_sensors(bridge);
> ret = -EINVAL;
> - goto err_out;
> + goto err_put_adev;
> }
>
> sensor = &bridge->sensors[bridge->n_sensors];
> - sensor->adev = adev;
> strscpy(sensor->name, cfg->hid, sizeof(sensor->name));
>
> ret = cio2_bridge_read_acpi_buffer(adev, "SSDB",
> @@ -214,6 +212,7 @@ static int cio2_bridge_connect_sensor(const struct cio2_sensor_config *cfg,
> goto err_free_swnodes;
> }
>
> + sensor->adev = acpi_dev_get(adev);
> adev->fwnode.secondary = fwnode;
>
> dev_info(&cio2->dev, "Found supported sensor %s\n",
> @@ -227,8 +226,7 @@ static int cio2_bridge_connect_sensor(const struct cio2_sensor_config *cfg,
> err_free_swnodes:
> software_node_unregister_nodes(sensor->swnodes);
> err_put_adev:
> - acpi_dev_put(sensor->adev);
> -err_out:
> + acpi_dev_put(adev);
> return ret;
> }
>
> diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> index 3a82faac5767..bff6a11bb21f 100644
> --- a/include/acpi/acpi_bus.h
> +++ b/include/acpi/acpi_bus.h
> @@ -698,11 +698,6 @@ acpi_dev_get_first_match_dev(const char *hid, const char *uid, s64 hrv);
> * @hrv: Hardware Revision of the device, pass -1 to not check _HRV
> *
> * The caller is responsible for invoking acpi_dev_put() on the returned device.
> - *
> - * FIXME: Due to above requirement there is a window that may invalidate @adev
> - * and next iteration will use a dangling pointer, e.g. in the case of a
> - * hotplug event. That said, the caller should ensure that this will never
> - * happen.
> */
> #define for_each_acpi_dev_match(adev, hid, uid, hrv) \
> for (adev = acpi_dev_get_first_match_dev(hid, uid, hrv); \
> --
> 2.31.1
>
On Thu, May 20, 2021 at 9:13 PM Rafael J. Wysocki <[email protected]> wrote:
>
> On Wed, May 19, 2021 at 11:19 PM Andy Shevchenko
> <[email protected]> wrote:
> >
> > Currently it's possible to iterate over the dangling pointer in case the device
> > suddenly disappears. This may happen becase callers put it at the end of a loop.
> >
> > Instead, let's move that call inside acpi_dev_get_next_match_dev().
>
> Not really.
OK, I see what you want to achieve and the macro is actually buggy,
because it leaves unbalanced references behind.
> > Fixes: 803abec64ef9 ("media: ipu3-cio2: Add cio2-bridge to ipu3-cio2 driver")
> > Fixes: bf263f64e804 ("media: ACPI / bus: Add acpi_dev_get_next_match_dev() and helper macro")
> > Cc: Daniel Scally <[email protected]>
> > Cc: Sakari Ailus <[email protected]>
> > Signed-off-by: Andy Shevchenko <[email protected]>
> > ---
> > drivers/acpi/utils.c | 5 +----
> > drivers/media/pci/intel/ipu3/cio2-bridge.c | 8 +++-----
> > include/acpi/acpi_bus.h | 5 -----
> > 3 files changed, 4 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
> > index 3b54b8fd7396..ccfc484dbffd 100644
> > --- a/drivers/acpi/utils.c
> > +++ b/drivers/acpi/utils.c
> > @@ -846,10 +846,6 @@ EXPORT_SYMBOL(acpi_dev_present);
> > * Return the next match of ACPI device if another matching device was present
> > * at the moment of invocation, or NULL otherwise.
> > *
> > - * FIXME: The function does not tolerate the sudden disappearance of @adev, e.g.
> > - * in the case of a hotplug event. That said, the caller should ensure that
> > - * this will never happen.
> > - *
> > * The caller is responsible for invoking acpi_dev_put() on the returned device.
> > *
> > * See additional information in acpi_dev_present() as well.
But the kerneldoc really needs to say that the caller is required to
obtain a reference on adev before passing it here, because that
reference will be dropped and the object pointed to by adev may not be
present any more after this returns.
> > @@ -866,6 +862,7 @@ acpi_dev_get_next_match_dev(struct acpi_device *adev, const char *hid, const cha
> > match.hrv = hrv;
> >
> > dev = bus_find_device(&acpi_bus_type, start, &match, acpi_dev_match_cb);
> > + acpi_dev_put(adev);
Hi Rafael, Andy
On 20/05/2021 20:40, Rafael J. Wysocki wrote:
> On Thu, May 20, 2021 at 9:13 PM Rafael J. Wysocki <[email protected]> wrote:
>> On Wed, May 19, 2021 at 11:19 PM Andy Shevchenko
>> <[email protected]> wrote:
>>> Currently it's possible to iterate over the dangling pointer in case the device
>>> suddenly disappears. This may happen becase callers put it at the end of a loop.
>>>
>>> Instead, let's move that call inside acpi_dev_get_next_match_dev().
>> Not really.
> OK, I see what you want to achieve and the macro is actually buggy,
> because it leaves unbalanced references behind.
Yeah; I guess the originally intended use (which was "get all these
devices") doesn't really tally with the naming or with the operation of
similar functions in the kernel like the fwnode_handle ops; sorry about
that. Anyway; I think Andy's fix is the right way to do it, so the
calling code's responsible for holding onto a reference if it wants to
keep it.
>
>>> Fixes: 803abec64ef9 ("media: ipu3-cio2: Add cio2-bridge to ipu3-cio2 driver")
>>> Fixes: bf263f64e804 ("media: ACPI / bus: Add acpi_dev_get_next_match_dev() and helper macro")
>>> Cc: Daniel Scally <[email protected]>
>>> Cc: Sakari Ailus <[email protected]>
>>> Signed-off-by: Andy Shevchenko <[email protected]>
>>> ---
>>> drivers/acpi/utils.c | 5 +----
>>> drivers/media/pci/intel/ipu3/cio2-bridge.c | 8 +++-----
>>> include/acpi/acpi_bus.h | 5 -----
>>> 3 files changed, 4 insertions(+), 14 deletions(-)
>>>
>>> diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
>>> index 3b54b8fd7396..ccfc484dbffd 100644
>>> --- a/drivers/acpi/utils.c
>>> +++ b/drivers/acpi/utils.c
>>> @@ -846,10 +846,6 @@ EXPORT_SYMBOL(acpi_dev_present);
>>> * Return the next match of ACPI device if another matching device was present
>>> * at the moment of invocation, or NULL otherwise.
>>> *
>>> - * FIXME: The function does not tolerate the sudden disappearance of @adev, e.g.
>>> - * in the case of a hotplug event. That said, the caller should ensure that
>>> - * this will never happen.
>>> - *
>>> * The caller is responsible for invoking acpi_dev_put() on the returned device.
>>> *
>>> * See additional information in acpi_dev_present() as well.
> But the kerneldoc really needs to say that the caller is required to
> obtain a reference on adev before passing it here, because that
> reference will be dropped and the object pointed to by adev may not be
> present any more after this returns.
>
>>> @@ -866,6 +862,7 @@ acpi_dev_get_next_match_dev(struct acpi_device *adev, const char *hid, const cha
>>> match.hrv = hrv;
>>>
>>> dev = bus_find_device(&acpi_bus_type, start, &match, acpi_dev_match_cb);
>>> + acpi_dev_put(adev);
On Wed, May 26, 2021 at 1:29 AM Daniel Scally <[email protected]> wrote:
> On 20/05/2021 20:40, Rafael J. Wysocki wrote:
> > On Thu, May 20, 2021 at 9:13 PM Rafael J. Wysocki <[email protected]> wrote:
> >> On Wed, May 19, 2021 at 11:19 PM Andy Shevchenko
> >> <[email protected]> wrote:
> >>> Currently it's possible to iterate over the dangling pointer in case the device
> >>> suddenly disappears. This may happen becase callers put it at the end of a loop.
> >>>
> >>> Instead, let's move that call inside acpi_dev_get_next_match_dev().
> >> Not really.
> > OK, I see what you want to achieve and the macro is actually buggy,
> > because it leaves unbalanced references behind.
>
>
> Yeah; I guess the originally intended use (which was "get all these
> devices") doesn't really tally with the naming or with the operation of
> similar functions in the kernel like the fwnode_handle ops; sorry about
> that. Anyway; I think Andy's fix is the right way to do it, so the
> calling code's responsible for holding onto a reference if it wants to
> keep it.
I think we need to postpone the fix till v5.14-rc1 is out. It appears
that some code has been changed in EFI and media subsystems so that
patch will be in conflict with.
--
With Best Regards,
Andy Shevchenko