Observes below crash while accessing (use-after-free) lock member
of bfq data.
context#1 context#2
process_one_work()
kthread() blk_mq_run_work_fn()
worker_thread() ->__blk_mq_run_hw_queue()
process_one_work() ->blk_mq_sched_dispatch_requests()
__blk_release_queue() ->blk_mq_do_dispatch_sched()
->__elevator_exit()
->blk_mq_exit_sched()
->exit_sched()
->kfree()
->bfq_dispatch_request()
->spin_unlock_irq(&bfqd->lock)
This is because of the kblockd delayed work that might got scheduled
around blk_release_queue() and accessed use-after-free member of
bfq_data.
240.212359: <2> Unable to handle kernel paging request at
virtual address ffffffee2e33ad70
...
240.212637: <2> Workqueue: kblockd blk_mq_run_work_fn
240.212649: <2> pstate: 00c00085 (nzcv daIf +PAN +UAO)
240.212666: <2> pc : queued_spin_lock_slowpath+0x10c/0x2e0
240.212677: <2> lr : queued_spin_lock_slowpath+0x84/0x2e0
...
Call trace:
240.212865: <2> queued_spin_lock_slowpath+0x10c/0x2e0
240.212876: <2> do_raw_spin_lock+0xf0/0xf4
240.212890: <2> _raw_spin_lock_irq+0x74/0x94
240.212906: <2> bfq_dispatch_request+0x4c/0xd60
240.212918: <2> blk_mq_do_dispatch_sched+0xe0/0x1f0
240.212927: <2> blk_mq_sched_dispatch_requests+0x130/0x194
240.212940: <2> __blk_mq_run_hw_queue+0x100/0x158
240.212950: <2> blk_mq_run_work_fn+0x1c/0x28
240.212963: <2> process_one_work+0x280/0x460
240.212973: <2> worker_thread+0x27c/0x4dc
240.212986: <2> kthread+0x160/0x170
Fix this by cancelling the delayed work if any before elevator exits.
Changes since V2:
- Retained the code logic and Reviewed-by signoff from V1 Patch
as per Ming comments.
- Moved the new local variables into queue_is_mq() branch.
- Removed 'cancel_delayed_work_sync' from blk_mq_hw_sysfs_release()
Changes since V1:
- Moved the logic into blk_cleanup_queue() as per Ming comments.
Signed-off-by: Pradeep P V K <ppvk@xxxxxxxxxxxxxx>
Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
block/blk-mq-sysfs.c | 1 -
block/blk-sysfs.c | 8 ++++++--
2 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
index 06222939..24bc9cc 100644
--- a/block/blk-mq-sysfs.c
+++ b/block/blk-mq-sysfs.c
@@ -36,7 +36,6 @@ static void blk_mq_hw_sysfs_release(struct kobject *kobj)
struct blk_mq_hw_ctx *hctx = container_of(kobj, struct blk_mq_hw_ctx,
kobj);
- cancel_delayed_work_sync(&hctx->run_work);
if (hctx->flags & BLK_MQ_F_BLOCKING)
cleanup_srcu_struct(hctx->srcu);
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 81722cd..73a2137 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -788,9 +788,13 @@ static void blk_release_queue(struct kobject *kobj)
blk_free_queue_stats(q->stats);
- if (queue_is_mq(q))
+ if (queue_is_mq(q)) {
+ struct blk_mq_hw_ctx *hctx;
+ int i;
cancel_delayed_work_sync(&q->requeue_work);
-
+ queue_for_each_hw_ctx(q, hctx, i)
+ cancel_delayed_work_sync(&hctx->run_work);
+ }
blk_exit_queue(q);
blk_queue_free_zone_bitmaps(q);
--
2.7.4
