This is a note to let you know that I've just added the patch titled
s390/cio: fix race condition during online processing
to the 6.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
s390-cio-fix-race-condition-during-online-processing.patch
and it can be found in the queue-6.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit b88d22b791a46e233f14a73eae7b3a073787e862
Author: Peter Oberparleiter <oberpar@xxxxxxxxxxxxx>
Date: Wed Apr 10 11:46:19 2024 +0200
s390/cio: fix race condition during online processing
[ Upstream commit 2d8527f2f911fab84aec04df4788c0c23af3df48 ]
A race condition exists in ccw_device_set_online() that can cause the
online process to fail, leaving the affected device in an inconsistent
state. As a result, subsequent attempts to set that device online fail
with return code ENODEV.
The problem occurs when a path verification request arrives after
a wait for final device state completed, but before the result state
is evaluated.
Fix this by ensuring that the CCW-device lock is held between
determining final state and checking result state.
Note that since:
commit 2297791c92d0 ("s390/cio: dont unregister subchannel from child-drivers")
path verification requests are much more likely to occur during boot,
resulting in an increased chance of this race condition occurring.
Fixes: 2297791c92d0 ("s390/cio: dont unregister subchannel from child-drivers")
Reviewed-by: Alexandra Winter <wintera@xxxxxxxxxxxxx>
Reviewed-by: Vineeth Vijayan <vneethv@xxxxxxxxxxxxx>
Signed-off-by: Peter Oberparleiter <oberpar@xxxxxxxxxxxxx>
Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/s390/cio/device.c b/drivers/s390/cio/device.c
index 0cfb179e1bcb6..34b2567b8df49 100644
--- a/drivers/s390/cio/device.c
+++ b/drivers/s390/cio/device.c
@@ -363,10 +363,8 @@ int ccw_device_set_online(struct ccw_device *cdev)
spin_lock_irq(cdev->ccwlock);
ret = ccw_device_online(cdev);
- spin_unlock_irq(cdev->ccwlock);
- if (ret == 0)
- wait_event(cdev->private->wait_q, dev_fsm_final_state(cdev));
- else {
+ if (ret) {
+ spin_unlock_irq(cdev->ccwlock);
CIO_MSG_EVENT(0, "ccw_device_online returned %d, "
"device 0.%x.%04x\n",
ret, cdev->private->dev_id.ssid,
@@ -375,7 +373,12 @@ int ccw_device_set_online(struct ccw_device *cdev)
put_device(&cdev->dev);
return ret;
}
- spin_lock_irq(cdev->ccwlock);
+ /* Wait until a final state is reached */
+ while (!dev_fsm_final_state(cdev)) {
+ spin_unlock_irq(cdev->ccwlock);
+ wait_event(cdev->private->wait_q, dev_fsm_final_state(cdev));
+ spin_lock_irq(cdev->ccwlock);
+ }
/* Check if online processing was successful */
if ((cdev->private->state != DEV_STATE_ONLINE) &&
(cdev->private->state != DEV_STATE_W4SENSE)) {
