Commit 813665564b3d ("iio: core: Convert to use firmware node handle
instead of OF node") switched the kind of nodes to use for label
retrieval in device registration. Probably an unwanted change in that
commit was that if the device has no parent then NULL pointer is
accessed. This is what happens in the stock IIO dummy driver when a
new entry is created in configfs:
# mkdir /sys/kernel/config/iio/devices/dummy/foo
BUG: kernel NULL pointer dereference, address: ...
...
Call Trace:
...
asm_exc_page_fault
container_offline
__iio_device_register
krealloc
iio_device_attach_buffer
iio_simple_dummy_configure_buffer
iio_triggered_buffer_setup_ext
iio_dummy_probe
iio_sw_device_create
device_make_group
configfs_mkdir
Since there seems to be no reason to make a parent device of an IIO
dummy device mandatory, let’s prevent the invalid memory access in
__iio_device_register when the parent device is NULL. With this
change, the IIO dummy driver works fine with configfs.
Fixes: 813665564b3d ("iio: core: Convert to use firmware node handle instead of OF node")
Signed-off-by: Milan Zamazal <[email protected]>
---
Changes in v2:
- Added a source comment about the dummy IIO device.
- Adjusted the backtrace cited in the commit message a bit.
- Replaced `... != NULL' condition with `...'.
- Dropped the unnecessary `fwnode != NULL' check (the involved calls
do the right thing when the argument is NULL).
---
drivers/iio/industrialio-core.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index c117f50d0cf3..adcba832e6fa 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -1888,7 +1888,7 @@ static const struct iio_buffer_setup_ops noop_ring_setup_ops;
int __iio_device_register(struct iio_dev *indio_dev, struct module *this_mod)
{
struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
- struct fwnode_handle *fwnode;
+ struct fwnode_handle *fwnode = NULL;
int ret;
if (!indio_dev->info)
@@ -1899,7 +1899,8 @@ int __iio_device_register(struct iio_dev *indio_dev, struct module *this_mod)
/* If the calling driver did not initialize firmware node, do it here */
if (dev_fwnode(&indio_dev->dev))
fwnode = dev_fwnode(&indio_dev->dev);
- else
+ /* The default dummy IIO device has no parent */
+ else if (indio_dev->dev.parent)
fwnode = dev_fwnode(indio_dev->dev.parent);
device_set_node(&indio_dev->dev, fwnode);
--
2.40.1
On Tue, Jul 18, 2023 at 05:29:17PM +0200, Milan Zamazal wrote:
> Commit 813665564b3d ("iio: core: Convert to use firmware node handle
> instead of OF node") switched the kind of nodes to use for label
> retrieval in device registration. Probably an unwanted change in that
> commit was that if the device has no parent then NULL pointer is
> accessed. This is what happens in the stock IIO dummy driver when a
> new entry is created in configfs:
> # mkdir /sys/kernel/config/iio/devices/dummy/foo
> BUG: kernel NULL pointer dereference, address: ...
> ...
> Call Trace:
> ...
> asm_exc_page_fault
> container_offline
> __iio_device_register
> krealloc
> iio_device_attach_buffer
> iio_simple_dummy_configure_buffer
> iio_triggered_buffer_setup_ext
> iio_dummy_probe
> iio_sw_device_create
> device_make_group
> configfs_mkdir
Please, remove more unrelated lines in this backtrace. Ideally it should come
to ~4-5. For example, you posted a command line, it's obvious that you run
configfs, so the last (two) line(s) of the backtrace are redundant.
Then drop basic stuff, like:
asm_exc_page_fault
container_offline
krealloc
Then remove unrelated IIO internals.
> Since there seems to be no reason to make a parent device of an IIO
> dummy device mandatory, let’s prevent the invalid memory access in
> __iio_device_register when the parent device is NULL. With this
> change, the IIO dummy driver works fine with configfs.
The code wise it's okay now, so after addressing above
Reviewed-by: Andy Shevchenko <[email protected]>
--
With Best Regards,
Andy Shevchenko