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 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
