6.5-stable review patch. If anyone has any objections, please let me know.
------------------
From: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
[ Upstream commit 6be6d112419713334ddd9c01f219ca16adaa4c76 ]
When nr_hw_queues shrink, we free the excess tags before realloc'ing
hw_ctxs for each queue. During that resize, we may need to access those
tags, like blk_mq_tag_idle(hctx) will access queue shared tags.
This can cause a slab use-after-free, as reported by KASAN. Fix it by
moving the releasing of excess tags to the end.
Fixes: e1dd7bc93029 ("blk-mq: fix tags leak when shrink nr_hw_queues")
Reported-by: Yi Zhang <yi.zhang@xxxxxxxxxx>
Closes: https://lore.kernel.org/all/CAHj4cs_CK63uoDpGBGZ6DN4OCTpzkR3UaVgK=LX8Owr8ej2ieQ@xxxxxxxxxxxxxx/
Cc: Ming Lei <ming.lei@xxxxxxxxxx>
Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
Link: https://lore.kernel.org/r/20230908005702.2183908-1-chengming.zhou@xxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
block/blk-mq.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -4404,11 +4404,8 @@ static int blk_mq_realloc_tag_set_tags(s
struct blk_mq_tags **new_tags;
int i;
- if (set->nr_hw_queues >= new_nr_hw_queues) {
- for (i = new_nr_hw_queues; i < set->nr_hw_queues; i++)
- __blk_mq_free_map_and_rqs(set, i);
+ if (set->nr_hw_queues >= new_nr_hw_queues)
goto done;
- }
new_tags = kcalloc_node(new_nr_hw_queues, sizeof(struct blk_mq_tags *),
GFP_KERNEL, set->numa_node);
@@ -4718,7 +4715,8 @@ static void __blk_mq_update_nr_hw_queues
{
struct request_queue *q;
LIST_HEAD(head);
- int prev_nr_hw_queues;
+ int prev_nr_hw_queues = set->nr_hw_queues;
+ int i;
lockdep_assert_held(&set->tag_list_lock);
@@ -4745,7 +4743,6 @@ static void __blk_mq_update_nr_hw_queues
blk_mq_sysfs_unregister_hctxs(q);
}
- prev_nr_hw_queues = set->nr_hw_queues;
if (blk_mq_realloc_tag_set_tags(set, nr_hw_queues) < 0)
goto reregister;
@@ -4781,6 +4778,10 @@ switch_back:
list_for_each_entry(q, &set->tag_list, tag_set_list)
blk_mq_unfreeze_queue(q);
+
+ /* Free the excess tags when nr_hw_queues shrink. */
+ for (i = set->nr_hw_queues; i < prev_nr_hw_queues; i++)
+ __blk_mq_free_map_and_rqs(set, i);
}
void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues)
