[PATCH] SCSI: fix queue cleanup race before scsi_requeue_run_queue is done

[zhengbin <zhengbin13@huawei.com>]

KASAN reports a use-after-free in 4.19-stable,
which won't happen after commit 47cdee29ef9d
("block: move blk_exit_queue into __blk_release_queue").
However, backport this patch to 4.19-stable will be a lot of work and
the risk is great. Moreover, we should make sure scsi_requeue_run_queue
is done before blk_cleanup_queue in master too.

BUG: KASAN: use-after-free in dd_has_work+0x50/0xe8
Read of size 8 at addr ffff808b57c6f168 by task kworker/53:1H/6910

CPU: 53 PID: 6910 Comm: kworker/53:1H Kdump: loaded Tainted: G
Hardware name: Huawei TaiShan 2280 /BC11SPCD, BIOS 1.59 01/31/2019
Workqueue: kblockd scsi_requeue_run_queue
Call trace:
 dump_backtrace+0x0/0x270
 show_stack+0x24/0x30
 dump_stack+0xb4/0xe4
 print_address_description+0x68/0x278
 kasan_report+0x204/0x330
 __asan_load8+0x88/0xb0
 dd_has_work+0x50/0xe8
 blk_mq_run_hw_queue+0x19c/0x218
 blk_mq_run_hw_queues+0x7c/0xb0
 scsi_run_queue+0x3ec/0x520
 scsi_requeue_run_queue+0x2c/0x38
 process_one_work+0x2e4/0x6d8
 worker_thread+0x6c/0x6a8
 kthread+0x1b4/0x1c0
 ret_from_fork+0x10/0x18

Allocated by task 46843:
 kasan_kmalloc+0xe0/0x190
 kmem_cache_alloc_node_trace+0x10c/0x258
 dd_init_queue+0x68/0x190
 blk_mq_init_sched+0x1cc/0x300
 elevator_init_mq+0x90/0xe0
 blk_mq_init_allocated_queue+0x700/0x728
 blk_mq_init_queue+0x48/0x90
 scsi_mq_alloc_queue+0x34/0xb0
 scsi_alloc_sdev+0x340/0x530
 scsi_probe_and_add_lun+0x46c/0x1260
 __scsi_scan_target+0x1b8/0x7b0
 scsi_scan_target+0x140/0x150
 fc_scsi_scan_rport+0x164/0x178 [scsi_transport_fc]
 process_one_work+0x2e4/0x6d8
 worker_thread+0x6c/0x6a8
 kthread+0x1b4/0x1c0
 ret_from_fork+0x10/0x18

Freed by task 46843:
 __kasan_slab_free+0x120/0x228
 kasan_slab_free+0x10/0x18
 kfree+0x88/0x218
 dd_exit_queue+0x5c/0x78
 blk_mq_exit_sched+0x104/0x130
 elevator_exit+0xa8/0xc8
 blk_exit_queue+0x48/0x78
 blk_cleanup_queue+0x170/0x248
 __scsi_remove_device+0x84/0x1b0
 scsi_probe_and_add_lun+0xd00/0x1260
 __scsi_scan_target+0x1b8/0x7b0
 scsi_scan_target+0x140/0x150
 fc_scsi_scan_rport+0x164/0x178 [scsi_transport_fc]
 process_one_work+0x2e4/0x6d8
 worker_thread+0x6c/0x6a8
 kthread+0x1b4/0x1c0
 ret_from_fork+0x10/0x18

Fixes: 8dc765d438f1 ("SCSI: fix queue cleanup race before queue initialization is done")
Signed-off-by: zhengbin <zhengbin13@huawei.com>
---
 drivers/scsi/scsi_lib.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 11e64b5..e5ef180 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -531,6 +531,11 @@ void scsi_requeue_run_queue(struct work_struct *work)
 	sdev = container_of(work, struct scsi_device, requeue_work);
 	q = sdev->request_queue;
 	scsi_run_queue(q);
+	/*
+	 * need to put q_usage_counter which
+	 * is got in scsi_end_request.
+	 */
+	percpu_ref_put(&q->q_usage_counter);
 }

 void scsi_run_host_queues(struct Scsi_Host *shost)
@@ -615,10 +620,11 @@ static bool scsi_end_request(struct request *req, blk_status_t error,
 	if (scsi_target(sdev)->single_lun ||
 	    !list_empty(&sdev->host->starved_list))
 		kblockd_schedule_work(&sdev->requeue_work);
-	else
+	else {
 		blk_mq_run_hw_queues(q, true);
+		percpu_ref_put(&q->q_usage_counter);
+	}

-	percpu_ref_put(&q->q_usage_counter);
 	return false;
 }

--
2.7.4