blk-iocost: fix UAF in ioc_pd_free

hulk inclusion
category: bugfix
bugzilla: 188032, https://gitee.com/openeuler/kernel/issues/I64T3E
CVE: NA

--------------------------------

Our test found the following problem in kernel 5.10:

  BUG: KASAN: use-after-free in _raw_spin_lock_irqsave+0x71/0xe0
  Write of size 4 at addr ffff8881432000e0 by task swapper/4/0
  ...
  Call Trace:
   <IRQ>
   dump_stack+0x9c/0xd3
   print_address_description.constprop.0+0x19/0x170
   __kasan_report.cold+0x6c/0x84
   kasan_report+0x3a/0x50
   check_memory_region+0xfd/0x1f0
   _raw_spin_lock_irqsave+0x71/0xe0
   ioc_pd_free+0x9d/0x250
   blkg_free.part.0+0x80/0x100
   __blkg_release+0xf3/0x1c0
   rcu_do_batch+0x292/0x700
   rcu_core+0x270/0x2d0
   __do_softirq+0xfd/0x402
    </IRQ>
   asm_call_irq_on_stack+0x12/0x20
   do_softirq_own_stack+0x37/0x50
   irq_exit_rcu+0x134/0x1a0
   sysvec_apic_timer_interrupt+0x36/0x80
   asm_sysvec_apic_timer_interrupt+0x12/0x20

   Freed by task 57:
   kfree+0xba/0x680
   rq_qos_exit+0x5a/0x80
   blk_cleanup_queue+0xce/0x1a0
   virtblk_remove+0x77/0x130 [virtio_blk]
   virtio_dev_remove+0x56/0xe0
   __device_release_driver+0x2ba/0x450
   device_release_driver+0x29/0x40
   bus_remove_device+0x1d8/0x2c0
   device_del+0x333/0x7e0
   device_unregister+0x27/0x90
   unregister_virtio_device+0x22/0x40
   virtio_pci_remove+0x53/0xb0
   pci_device_remove+0x7a/0x130
   __device_release_driver+0x2ba/0x450
   device_release_driver+0x29/0x40
   pci_stop_bus_device+0xcf/0x100
   pci_stop_and_remove_bus_device+0x16/0x20
   disable_slot+0xa1/0x110
   acpiphp_disable_and_eject_slot+0x35/0xe0
   hotplug_event+0x1b8/0x3c0
   acpiphp_hotplug_notify+0x37/0x70
   acpi_device_hotplug+0xee/0x320
   acpi_hotplug_work_fn+0x69/0x80
   process_one_work+0x3c5/0x730
   worker_thread+0x93/0x650
   kthread+0x1ba/0x210
   ret_from_fork+0x22/0x30

It happened as follow:

        T1            T2              T3	    T4
  //delete device
  del_gendisk
   bdi_unregister
    bdi_remove_from_list
     synchronize_rcu_expedited

               //rmdir cgroup
               blkcg_destroy_blkgs
                blkg_destroy
                 percpu_ref_kill
                  blkg_release
                   call_rcu
				blk_cleanup_queue
       			          rq_qos_exit
			           ioc_rqos_exit
			            kfree(ioc)
					    __blkg_release
                           		     blkg_free
                           		      blkg_free_workfn
                           		       pd_free_fn
                           		        ioc_pd_free
						 spin_lock_irqsave
						  ->ioc is freed

Fix the problem by moving the operation on ioc in ioc_pd_free() to
ioc_pd_offline(), and just free resource in ioc_pd_free() like iolatency
and throttle.

Fixes: 7caa4715 ("blkcg: implement blk-iocost")
Signed-off-by: NLi Nan <linan122@huawei.com>
(cherry picked from commit 4c2d16fb)

block/blk-iocost.c

@@ -2964,7 +2964,7 @@ static void ioc_pd_init(struct blkg_policy_data *pd)
 	spin_unlock_irqrestore(&ioc->lock, flags);
 }
 
-static void ioc_pd_free(struct blkg_policy_data *pd)
+static void ioc_pd_offline(struct blkg_policy_data *pd)
 {
 	struct ioc_gq *iocg = pd_to_iocg(pd);
 	struct ioc *ioc = iocg->ioc;
@@ -2988,6 +2988,12 @@ static void ioc_pd_free(struct blkg_policy_data *pd)
 
 		hrtimer_cancel(&iocg->waitq_timer);
 	}
+}
+
+static void ioc_pd_free(struct blkg_policy_data *pd)
+{
+	struct ioc_gq *iocg = pd_to_iocg(pd);
+
 	free_percpu(iocg->pcpu_stat);
 	kfree(iocg);
 }
@@ -3468,6 +3474,7 @@ static struct blkcg_policy blkcg_policy_iocost = {
 	.cpd_free_fn	= ioc_cpd_free,
 	.pd_alloc_fn	= ioc_pd_alloc,
 	.pd_init_fn	= ioc_pd_init,
+	.pd_offline_fn	= ioc_pd_offline,
 	.pd_free_fn	= ioc_pd_free,
 	.pd_stat_fn	= ioc_pd_stat,
 };