Re: [PATCH -next 7/8] blk-iocost: fix possible UAF in ioc_pd_free

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在 2022/11/28 23:44, Li Nan 写道:
Our test found the following problem in kernel 5.10, and the same problem
should exist in mainline:

   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
   //rmdir cgroup
   blkcg_destroy_blkgs
    blkg_destroy
     percpu_ref_kill
      blkg_release
       call_rcu
			//delete device
			del_gendisk

del_gendisk will synchronize_rcu, hence this is wrong.

call_rcu from blkcg_destroy_blkgs should be called after
synchronize_rcu.

Thanks,
Kuai
			 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.

Signed-off-by: Li Nan <linan122@xxxxxxxxxx>
---
  block/blk-iocost.c | 9 ++++++++-
  1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 03977385449f..1b855babfc35 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -2978,7 +2978,7 @@ 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;
@@ -3002,6 +3002,12 @@ 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);
  }
@@ -3488,6 +3494,7 @@ 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,
  };





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