[PATCH v2 1/1] ACPI: utils: Fix reference counting in for_each_acpi_dev_match()

[PATCH v2 1/1] ACPI: utils: Fix reference counting in for_each_acpi_dev_match()

[Andy Shevchenko]

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")
Fixes: edbd1bc4951e ("efi/dev-path-parser: Switch to use for_each_acpi_dev_match()")
Signed-off-by: Andy Shevchenko <andy.shevchenko@gmail.com>
---
v2:
- rebased on top of v5.14-rc1 and hence added fix for EFI code
- added kernel documentation update to point out that
  acpi_dev_get_next_match_dev() drops a reference on the given
  ACPI device (Rafael)

 drivers/acpi/utils.c                       | 7 +++----
 drivers/firmware/efi/dev-path-parser.c     | 1 -
 drivers/media/pci/intel/ipu3/cio2-bridge.c | 6 ++----
 include/acpi/acpi_bus.h                    | 5 -----
 4 files changed, 5 insertions(+), 14 deletions(-)

diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
index e7ddd281afff..d5cedffeeff9 100644
--- a/drivers/acpi/utils.c
+++ b/drivers/acpi/utils.c
@@ -860,11 +860,9 @@ 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.
+ * On the other hand the function invokes  acpi_dev_put() on the given @adev
+ * assuming that its reference counter had been increased beforehand.
  *
  * See additional information in acpi_dev_present() as well.
  */
@@ -880,6 +878,7 @@ 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/firmware/efi/dev-path-parser.c b/drivers/firmware/efi/dev-path-parser.c
index 10d4457417a4..eb9c65f97841 100644
--- a/drivers/firmware/efi/dev-path-parser.c
+++ b/drivers/firmware/efi/dev-path-parser.c
@@ -34,7 +34,6 @@ static long __init parse_acpi_path(const struct efi_dev_path *node,
 			break;
 		if (!adev->pnp.unique_id && node->acpi.uid == 0)
 			break;
-		acpi_dev_put(adev);
 	}
 	if (!adev)
 		return -ENODEV;
diff --git a/drivers/media/pci/intel/ipu3/cio2-bridge.c b/drivers/media/pci/intel/ipu3/cio2-bridge.c
index 4657e99df033..59a36f922675 100644
--- a/drivers/media/pci/intel/ipu3/cio2-bridge.c
+++ b/drivers/media/pci/intel/ipu3/cio2-bridge.c
@@ -173,10 +173,8 @@ static int cio2_bridge_connect_sensor(const struct cio2_sensor_config *cfg,
 	int ret;
 
 	for_each_acpi_dev_match(adev, cfg->hid, NULL, -1) {
-		if (!adev->status.enabled) {
-			acpi_dev_put(adev);
+		if (!adev->status.enabled)
 			continue;
-		}
 
 		if (bridge->n_sensors >= CIO2_NUM_PORTS) {
 			acpi_dev_put(adev);
@@ -185,7 +183,6 @@ static int cio2_bridge_connect_sensor(const struct cio2_sensor_config *cfg,
 		}
 
 		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",
@@ -215,6 +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",
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index 1ae993fee4a5..b9d434a93632 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -707,11 +707,6 @@ 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);	\
-- 
2.32.0

Re: [PATCH v2 1/1] ACPI: utils: Fix reference counting in for_each_acpi_dev_match()

[Daniel Scally]

Hi Andy - thanks for fixing this

On 12/07/2021 19:21, Andy Shevchenko 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().
>
> 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")
> Fixes: edbd1bc4951e ("efi/dev-path-parser: Switch to use for_each_acpi_dev_match()")
> Signed-off-by: Andy Shevchenko <andy.shevchenko@gmail.com>

Reviewed-by: Daniel Scally <djrscally@gmail.com>


> ---
> v2:
> - rebased on top of v5.14-rc1 and hence added fix for EFI code
> - added kernel documentation update to point out that
>   acpi_dev_get_next_match_dev() drops a reference on the given
>   ACPI device (Rafael)
>
>  drivers/acpi/utils.c                       | 7 +++----
>  drivers/firmware/efi/dev-path-parser.c     | 1 -
>  drivers/media/pci/intel/ipu3/cio2-bridge.c | 6 ++----
>  include/acpi/acpi_bus.h                    | 5 -----
>  4 files changed, 5 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
> index e7ddd281afff..d5cedffeeff9 100644
> --- a/drivers/acpi/utils.c
> +++ b/drivers/acpi/utils.c
> @@ -860,11 +860,9 @@ 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.
> + * On the other hand the function invokes  acpi_dev_put() on the given @adev
> + * assuming that its reference counter had been increased beforehand.
>   *
>   * See additional information in acpi_dev_present() as well.
>   */
> @@ -880,6 +878,7 @@ 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/firmware/efi/dev-path-parser.c b/drivers/firmware/efi/dev-path-parser.c
> index 10d4457417a4..eb9c65f97841 100644
> --- a/drivers/firmware/efi/dev-path-parser.c
> +++ b/drivers/firmware/efi/dev-path-parser.c
> @@ -34,7 +34,6 @@ static long __init parse_acpi_path(const struct efi_dev_path *node,
>  			break;
>  		if (!adev->pnp.unique_id && node->acpi.uid == 0)
>  			break;
> -		acpi_dev_put(adev);
>  	}
>  	if (!adev)
>  		return -ENODEV;
> diff --git a/drivers/media/pci/intel/ipu3/cio2-bridge.c b/drivers/media/pci/intel/ipu3/cio2-bridge.c
> index 4657e99df033..59a36f922675 100644
> --- a/drivers/media/pci/intel/ipu3/cio2-bridge.c
> +++ b/drivers/media/pci/intel/ipu3/cio2-bridge.c
> @@ -173,10 +173,8 @@ static int cio2_bridge_connect_sensor(const struct cio2_sensor_config *cfg,
>  	int ret;
>  
>  	for_each_acpi_dev_match(adev, cfg->hid, NULL, -1) {
> -		if (!adev->status.enabled) {
> -			acpi_dev_put(adev);
> +		if (!adev->status.enabled)
>  			continue;
> -		}
>  
>  		if (bridge->n_sensors >= CIO2_NUM_PORTS) {
>  			acpi_dev_put(adev);
> @@ -185,7 +183,6 @@ static int cio2_bridge_connect_sensor(const struct cio2_sensor_config *cfg,
>  		}
>  
>  		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",
> @@ -215,6 +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",
> diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> index 1ae993fee4a5..b9d434a93632 100644
> --- a/include/acpi/acpi_bus.h
> +++ b/include/acpi/acpi_bus.h
> @@ -707,11 +707,6 @@ 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);	\

Re: [PATCH v2 1/1] ACPI: utils: Fix reference counting in for_each_acpi_dev_match()

[Rafael J. Wysocki]

On Wed, Jul 14, 2021 at 12:32 AM Daniel Scally <djrscally@gmail.com> wrote:
>
> Hi Andy - thanks for fixing this
>
> On 12/07/2021 19:21, Andy Shevchenko 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().
> >
> > 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")
> > Fixes: edbd1bc4951e ("efi/dev-path-parser: Switch to use for_each_acpi_dev_match()")
> > Signed-off-by: Andy Shevchenko <andy.shevchenko@gmail.com>
>
> Reviewed-by: Daniel Scally <djrscally@gmail.com>

Applied as 5.14-rc material, thanks!

> > ---
> > v2:
> > - rebased on top of v5.14-rc1 and hence added fix for EFI code
> > - added kernel documentation update to point out that
> >   acpi_dev_get_next_match_dev() drops a reference on the given
> >   ACPI device (Rafael)
> >
> >  drivers/acpi/utils.c                       | 7 +++----
> >  drivers/firmware/efi/dev-path-parser.c     | 1 -
> >  drivers/media/pci/intel/ipu3/cio2-bridge.c | 6 ++----
> >  include/acpi/acpi_bus.h                    | 5 -----
> >  4 files changed, 5 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
> > index e7ddd281afff..d5cedffeeff9 100644
> > --- a/drivers/acpi/utils.c
> > +++ b/drivers/acpi/utils.c
> > @@ -860,11 +860,9 @@ 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.
> > + * On the other hand the function invokes  acpi_dev_put() on the given @adev
> > + * assuming that its reference counter had been increased beforehand.
> >   *
> >   * See additional information in acpi_dev_present() as well.
> >   */
> > @@ -880,6 +878,7 @@ 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/firmware/efi/dev-path-parser.c b/drivers/firmware/efi/dev-path-parser.c
> > index 10d4457417a4..eb9c65f97841 100644
> > --- a/drivers/firmware/efi/dev-path-parser.c
> > +++ b/drivers/firmware/efi/dev-path-parser.c
> > @@ -34,7 +34,6 @@ static long __init parse_acpi_path(const struct efi_dev_path *node,
> >                       break;
> >               if (!adev->pnp.unique_id && node->acpi.uid == 0)
> >                       break;
> > -             acpi_dev_put(adev);
> >       }
> >       if (!adev)
> >               return -ENODEV;
> > diff --git a/drivers/media/pci/intel/ipu3/cio2-bridge.c b/drivers/media/pci/intel/ipu3/cio2-bridge.c
> > index 4657e99df033..59a36f922675 100644
> > --- a/drivers/media/pci/intel/ipu3/cio2-bridge.c
> > +++ b/drivers/media/pci/intel/ipu3/cio2-bridge.c
> > @@ -173,10 +173,8 @@ static int cio2_bridge_connect_sensor(const struct cio2_sensor_config *cfg,
> >       int ret;
> >
> >       for_each_acpi_dev_match(adev, cfg->hid, NULL, -1) {
> > -             if (!adev->status.enabled) {
> > -                     acpi_dev_put(adev);
> > +             if (!adev->status.enabled)
> >                       continue;
> > -             }
> >
> >               if (bridge->n_sensors >= CIO2_NUM_PORTS) {
> >                       acpi_dev_put(adev);
> > @@ -185,7 +183,6 @@ static int cio2_bridge_connect_sensor(const struct cio2_sensor_config *cfg,
> >               }
> >
> >               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",
> > @@ -215,6 +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",
> > diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> > index 1ae993fee4a5..b9d434a93632 100644
> > --- a/include/acpi/acpi_bus.h
> > +++ b/include/acpi/acpi_bus.h
> > @@ -707,11 +707,6 @@ 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);        \