From: Stefan Haberland <sth@linux.ibm.com>
Date: Thu, 17 Dec 2020 16:59:06 +0100
Subject: s390/dasd: fix list corruption of pavgroup group list
Git-commit: 0ede91f83aa335da1c3ec68eb0f9e228f269f6d8
Patch-mainline: v5.11-rc1
References: git-fixes
dasd_alias_add_device() moves devices to the active_devices list in case
of a scheduled LCU update regardless if they have previously been in a
pavgroup or not.
Example: device A and B are in the same pavgroup.
Device A has already been in a pavgroup and the private->pavgroup pointer
is set and points to a valid pavgroup. While going through dasd_add_device
it is moved from the pavgroup to the active_devices list.
In parallel device B might be removed from the same pavgroup in
remove_device_from_lcu() which in turn checks if the group is empty
and deletes it accordingly because device A has already been removed from
there.
When now device A enters remove_device_from_lcu() it is tried to remove it
from the pavgroup again because the pavgroup pointer is still set and again
the empty group will be cleaned up which leads to a list corruption.
Fix by setting private->pavgroup to NULL in dasd_add_device.
If the device has been the last device on the pavgroup an empty pavgroup
remains but this will be cleaned up by the scheduled lcu_update which
iterates over all existing pavgroups.
Fixes: 8e09f21574ea ("[S390] dasd: add hyper PAV support to DASD device driver, part 1")
Cc: stable@vger.kernel.org
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Reviewed-by: Jan Hoeppner <hoeppner@linux.ibm.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
drivers/s390/block/dasd_alias.c | 1 +
1 file changed, 1 insertion(+)
--- a/drivers/s390/block/dasd_alias.c
+++ b/drivers/s390/block/dasd_alias.c
@@ -634,6 +634,7 @@ int dasd_alias_add_device(struct dasd_de
}
if (lcu->flags & UPDATE_PENDING) {
list_move(&device->alias_list, &lcu->active_devices);
+ private->pavgroup = NULL;
_schedule_lcu_update(lcu, device);
}
spin_unlock_irqrestore(&lcu->lock, flags);