Hi,
On 5/15/21 8:57 AM, Alexandru Ardelean wrote:
> On Fri, May 14, 2021 at 11:36 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
>>
>> Removing an iio-driver module (or unbinding the driver) causes a BUG() to
>> trigger when the kernel is build with list-debugging enabled. This is
>> caused by a double list_del() introduced by commit 8dedcc3eee3a ("iio:
>> core: centralize ioctl() calls to the main chardev").
>>
>> This patch introduces an ioctl_handlers list to which ioctl handlers are
>> added. The cleanup of these however happens twice.
>>
>> The 2 registration functions:
>> iio_device_ioctl_handler_register()
>> iio_device_register_eventset()
>>
>> Have matching unregister functions which do a list_del on the head added
>> to the list; and iio_device_unregister() has:
>>
>> list_for_each_entry_safe(h, t, &iio_dev_opaque->ioctl_handlers, entry)
>> list_del(&h->entry);
>
> This patch should already be in the fixes-togreg tree of IIO.
> I am not sure when/if it went in next.
>
> https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/commit/?h=fixes-togreg&id=901f84de0e16bde10a72d7eb2f2eb73fcde8fa1a
Ah, interesting that 2 people managed to hit this issue at more or less
the same time, given that the bug has been present for a while now.
Anyways I'm happy that a fix for this is on its way already :)
Regards,
Hans
>
>>
>> This is a problem because iio_device_unregister() does this before calling
>> iio_buffers_free_sysfs_and_mask() which calls
>> iio_device_ioctl_handler_unregister() which calls list_del on the entry
>> added by iio_buffers_alloc_sysfs_and_mask() a second time causing this:
>>
>> [root@fedora ~]# rmmod bmc150_accel_i2c
>> Segmentation fault
>>
>> [ 160.627546] ------------[ cut here ]------------
>> [ 160.627549] kernel BUG at lib/list_debug.c:45!
>> [ 160.629125] invalid opcode: 0000 [#1] SMP PTI
>> [ 160.629140] CPU: 0 PID: 1139 Comm: rmmod Tainted: G E 5.13.0-rc1+ #341
>> [ 160.629146] Hardware name: LENOVO 80M1/Mini, BIOS C7CN31WW 08/05/2016
>> [ 160.629149] RIP: 0010:__list_del_entry_valid.cold+0xf/0x47
>> ...
>> [ 160.629202] Call Trace:
>> [ 160.629209] iio_device_ioctl_handler_unregister+0xe/0x90 [industrialio]
>> [ 160.629226] iio_device_unregister_trigger_consumer+0x21d/0x2f0 [industrialio]
>> [ 160.629239] bmc150_accel_core_remove+0x20/0xd0 [bmc150_accel_core]
>> [ 160.629246] i2c_device_remove+0x25/0xb0
>> [ 160.629254] __device_release_driver+0x180/0x240
>> [ 160.629261] device_release_driver+0x26/0x40
>> [ 160.629267] bus_remove_device+0xf2/0x160
>> [ 160.629272] device_del+0x18c/0x3e0
>> [ 160.629280] device_unregister+0x16/0x60
>> ...
>>
>> Since iio_device_ioctl_handler_unregister/iio_device_unregister_eventset()
>> already do the list_del() there is no need for the
>> list_for_each_entry_safe() in iio_device_unregister() which also does the
>> list_del(). Remove the list_for_each_entry_safe() to fix the double
>> list_del() issue.
>>
>> Fixes: 8dedcc3eee3a ("iio: core: centralize ioctl() calls to the main chardev")
>> Cc: Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>
>> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
>> ---
>> drivers/iio/industrialio-core.c | 6 ------
>> 1 file changed, 6 deletions(-)
>>
>> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
>> index d92c58a94fe4..9e59f5da3d28 100644
>> --- a/drivers/iio/industrialio-core.c
>> +++ b/drivers/iio/industrialio-core.c
>> @@ -1926,9 +1926,6 @@ EXPORT_SYMBOL(__iio_device_register);
>> **/
>> void iio_device_unregister(struct iio_dev *indio_dev)
>> {
>> - struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
>> - struct iio_ioctl_handler *h, *t;
>> -
>> cdev_device_del(&indio_dev->chrdev, &indio_dev->dev);
>>
>> mutex_lock(&indio_dev->info_exist_lock);
>> @@ -1939,9 +1936,6 @@ void iio_device_unregister(struct iio_dev *indio_dev)
>>
>> indio_dev->info = NULL;
>>
>> - list_for_each_entry_safe(h, t, &iio_dev_opaque->ioctl_handlers, entry)
>> - list_del(&h->entry);
>> -
>> iio_device_wakeup_eventset(indio_dev);
>> iio_buffer_wakeup_poll(indio_dev);
>>
>> --
>> 2.31.1
>>
>
