Nuno Sá <noname.nuno@xxxxxxxxx> writes:
> On Tue, 2023-07-18 at 14:07 +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: 0000000000000278
>> ...
>> ? asm_exc_page_fault+0x22/0x30
>> ? container_offline+0x20/0x20
>> __iio_device_register+0x45/0xc10
>> ? krealloc+0x73/0xa0
>> ? iio_device_attach_buffer+0x31/0xc0
>> ? iio_simple_dummy_configure_buffer+0x20/0x20
>> ? iio_triggered_buffer_setup_ext+0xb4/0x100
>> iio_dummy_probe+0x112/0x190
>> iio_sw_device_create+0xa8/0xd0
>> device_make_group+0xe/0x40
>> configfs_mkdir+0x1a6/0x440
>>
>> 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 <mzamazal@xxxxxxxxxx>
>> ---
>
> LGTM (just one minor question below...)
>
> Reviewed-by: Nuno Sa <nuno.sa@xxxxxxxxxx>
>
>> drivers/iio/industrialio-core.c | 11 ++++++-----
>> 1 file changed, 6 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
>> index c117f50d0cf3..229527b3434a 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)
>> @@ -1899,11 +1899,12 @@ 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
>> + else if (indio_dev->dev.parent != NULL)
>
> Maybe this is odd enough that it could have an explicit comment referencing the
> iio-dummy device?
Good idea, also to not forget about iio-dummy generally. I'll add it.
> Not sure if there's any other place where this can actually happen...
>
> Apparently there are also some dev_err() on the parent device (even though
> dev_err() handles it) but yeah, unrelated with this.
>
>
> - Nuno Sá
