From: Giuliano Procida Date: Thu Jun 18 19:32:23 2020 +0100 Subject: blk-mq: move _blk_mq_update_nr_hw_queues synchronize_rcu call Patch-mainline: never, not needed upstream, android only References: CVE-2020-0433 bsc#1176720 This fixes the 4.14 backport commit 574eb136ec7f315c3ef2ca68fa9b3e16c56baa24 which was upstream commit f5bbbbe4d63577026f908a809f22f5fd5a90ea1f. The upstream commit added a call to synchronize_rcu to _blk_mq_update_nr_hw_queues, just after freezing queues. In the backport this landed just after unfreezeing queues. This commit moves the call to its intended place. [lduncan: this commit didn't make it upstream since the commit it fixes was changed there. But it's needed for this backport. See: https://android.googlesource.com/kernel/common/+/b609c7cecb71%5E%21/#F0 ] Fixes: 574eb136ec7f ("blk-mq: sync the update nr_hw_queues with blk_mq_queue_tag_busy_iter") Signed-off-by: Giuliano Procida Signed-off-by: Sasha Levin Acked-by: Lee Duncan --- --- block/blk-mq.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2777,10 +2777,6 @@ static void __blk_mq_update_nr_hw_queues list_for_each_entry(q, &set->tag_list, tag_set_list) blk_mq_freeze_queue(q); /* - * Sync with blk_mq_queue_tag_busy_iter. - */ - synchronize_rcu(); - /* * Switch IO scheduler to 'none', cleaning up the data associated * with the previous scheduler. We will switch back once we are done * updating the new sw to hw queue mappings. @@ -2821,6 +2817,11 @@ switch_back: list_for_each_entry(q, &set->tag_list, tag_set_list) blk_mq_unfreeze_queue(q); + + /* + * Sync with blk_mq_queue_tag_busy_iter. + */ + synchronize_rcu(); } void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues)