On Mon, Aug 19, 2019 at 10:39:05AM +0800, zhengbin wrote:
> 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.
I have backported that patchset to v4.18 based kernel, and it won't
take lots of work at all.
>
> 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 <[email protected]>
> ---
> drivers/scsi/scsi_lib.c | 24 ++++++++++++++++++------
> drivers/scsi/scsi_sysfs.c | 3 ++-
> 2 files changed, 20 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 75b926e..42f1475 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -208,7 +208,13 @@ static void __scsi_queue_insert(struct scsi_cmnd *cmd,
> int reason, bool unbusy)
> }
> spin_lock_irqsave(q->queue_lock, flags);
> blk_requeue_request(q, cmd->request);
> - kblockd_schedule_work(&device->requeue_work);
> + /*
> + * need to get q_usage_counter which will be
> + * put in scsi_requeue_run_queue.
> + */
> + percpu_ref_get(&q->q_usage_counter);
> + if (!kblockd_schedule_work(&device->requeue_work))
> + percpu_ref_put(&q->q_usage_counter);
> spin_unlock_irqrestore(q->queue_lock, flags);
> }
>
> @@ -548,6 +554,11 @@ 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 or __scsi_queue_insert.
> + */
> + percpu_ref_put(&q->q_usage_counter);
> }
>
> /*
> @@ -706,12 +717,13 @@ static bool scsi_end_request(struct request *req,
> blk_status_t error,
> __blk_mq_end_request(req, error);
>
> if (scsi_target(sdev)->single_lun ||
> - !list_empty(&sdev->host->starved_list))
> - kblockd_schedule_work(&sdev->requeue_work);
> - else
> + !list_empty(&sdev->host->starved_list)) {
> + if (!kblockd_schedule_work(&sdev->requeue_work))
> + percpu_ref_put(&q->q_usage_counter);
> + } else {
> blk_mq_run_hw_queues(q, true);
> -
> - percpu_ref_put(&q->q_usage_counter);
> + percpu_ref_put(&q->q_usage_counter);
> + }
> } else {
> unsigned long flags;
>
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> index 3aee946..2dc422e 100644
> --- a/drivers/scsi/scsi_sysfs.c
> +++ b/drivers/scsi/scsi_sysfs.c
> @@ -1392,7 +1392,8 @@ void __scsi_remove_device(struct scsi_device *sdev)
> mutex_unlock(&sdev->state_mutex);
>
> blk_cleanup_queue(sdev->request_queue);
> - cancel_work_sync(&sdev->requeue_work);
> + if (cancel_work_sync(&sdev->requeue_work))
> + percpu_ref_put(&sdev->request_queue->q_usage_counter);
>
> if (sdev->host->hostt->slave_destroy)
> sdev->host->hostt->slave_destroy(sdev);
Getting/putting the percpu ref from different contexts is just a
nightmare for maintaining the correctness.
Thanks,
Ming
