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SubjectRe: [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@huawei.com>
> ---
> 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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