On 2020-09-16 06:28, Ming Lei wrote:
On Mon, Sep 14, 2020 at 10:14 PM Pradeep P V K <ppvk@xxxxxxxxxxxxxx>
wrote:
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.
Signed-off-by: Pradeep P V K <ppvk@xxxxxxxxxxxxxx>
---
block/blk-sysfs.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 81722cd..e4a9aac 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -779,6 +779,8 @@ static void blk_release_queue(struct kobject
*kobj)
{
struct request_queue *q =
container_of(kobj, struct request_queue, kobj);
+ struct blk_mq_hw_ctx *hctx;
+ int i;
Please move the above two lines to the branch of 'if (queue_is_mq(q))
'.
Sure. i will address this in my next patch set.
might_sleep();
@@ -788,9 +790,11 @@ static void blk_release_queue(struct kobject
*kobj)
blk_free_queue_stats(q->stats);
- if (queue_is_mq(q))
+ if (queue_is_mq(q)) {
cancel_delayed_work_sync(&q->requeue_work);
-
+ queue_for_each_hw_ctx(q, hctx, i)
+ cancel_delayed_work_sync(&hctx->run_work);
+ }
Now the 'cancel_delayed_work_sync' from blk_mq_hw_sysfs_release() can
be killed meantime.
ok, i will remove this in my next patch set.
We have to call cancel_delayed_work_sync when reqeuest queue's
refcount drops to zero, otherwise
new run queue may be started somewhere, so feel free to add the
reviewed-by after the above two
comments are addressed.
Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
sure i will address those 2 comments and will retain your
Reviewed-by signoff on my next patch set.
Thanks,
Ming Lei
Thanks and Regards,
Pradeep
