Sender: Corey Minyard <tcminyard@gmail.com>
Date:   Mon, 20 Dec 2021 06:45:22 -0600
From:   Corey Minyard <minyard@acm.org>
To:     Wu Bo <wubo40@huawei.com>
Cc:     openipmi-developer@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, linfeilong@huawei.com
Subject: Re: [PATCH] ipmi: Fix UAF when uninstall ipmi_si and ipmi_msghandler
 module
Message-ID: <20211220124522.GS14936@minyard.net>
Reply-To: minyard@acm.org
References: <1639983320-34222-1-git-send-email-wubo40@huawei.com>
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I believe this has already been fixed by change 1d49eb91e 'ipmi: Move
remove_work to dedicated workqueue' by moving to a dedicated workqueue.
Can you test against the bleeding edge kernel and see?

Thanks,

-corey

On Mon, Dec 20, 2021 at 02:55:20PM +0800, Wu Bo wrote:
> Hi,
> 
> When testing install and uninstall of ipmi_si.ko and ipmi_msghandler.ko, 
> the system crashed.
> 
> The log as follows:
> [  141.087026] BUG: unable to handle kernel paging request at ffffffffc09b3a5a
> [  141.087241] PGD 8fe4c0d067 P4D 8fe4c0d067 PUD 8fe4c0f067 PMD 103ad89067 PTE 0
> [  141.087464] Oops: 0010 [#1] SMP NOPTI
> [  141.087580] CPU: 67 PID: 668 Comm: kworker/67:1 Kdump: loaded Not tainted 4.18.0.x86_64 #47
> [  141.088009] Workqueue: events 0xffffffffc09b3a40
> [  141.088009] RIP: 0010:0xffffffffc09b3a5a
> [  141.088009] Code: Bad RIP value.
> [  141.088009] RSP: 0018:ffffb9094e2c3e88 EFLAGS: 00010246
> [  141.088009] RAX: 0000000000000000 RBX: ffff9abfdb1f04a0 RCX: 0000000000000000
> [  141.088009] RDX: 0000000000000000 RSI: 0000000000000246 RDI: 0000000000000246
> [  141.088009] RBP: 0000000000000000 R08: ffff9abfffee3cb8 R09: 00000000000002e1
> [  141.088009] R10: ffffb9094cb73d90 R11: 00000000000f4240 R12: ffff9abfffee8700
> [  141.088009] R13: 0000000000000000 R14: ffff9abfdb1f04a0 R15: ffff9abfdb1f04a8
> [  141.088009] FS:  0000000000000000(0000) GS:ffff9abfffec0000(0000) knlGS:0000000000000000
> [  141.088009] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  141.088009] CR2: ffffffffc09b3a30 CR3: 0000008fe4c0a001 CR4: 00000000007606e0
> [  141.088009] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [  141.088009] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [  141.088009] PKRU: 55555554
> [  141.088009] Call Trace:
> [  141.088009]  ? process_one_work+0x195/0x390
> [  141.088009]  ? worker_thread+0x30/0x390
> [  141.088009]  ? process_one_work+0x390/0x390
> [  141.088009]  ? kthread+0x10d/0x130
> [  141.088009]  ? kthread_flush_work_fn+0x10/0x10
> [  141.088009]  ? ret_from_fork+0x35/0x40] BUG: unable to handle kernel paging request at ffffffffc0b28a5a
> [  200.223240] PGD 97fe00d067 P4D 97fe00d067 PUD 97fe00f067 PMD a580cbf067 PTE 0
> [  200.223464] Oops: 0010 [#1] SMP NOPTI
> [  200.223579] CPU: 63 PID: 664 Comm: kworker/63:1 Kdump: loaded Not tainted 4.18.0.x86_64 #46
> [  200.224008] Workqueue: events 0xffffffffc0b28a40
> [  200.224008] RIP: 0010:0xffffffffc0b28a5a
> [  200.224008] Code: Bad RIP value.
> [  200.224008] RSP: 0018:ffffbf3c8e2a3e88 EFLAGS: 00010246
> [  200.224008] RAX: 0000000000000000 RBX: ffffa0799ad6bca0 RCX: 0000000000000000
> [  200.224008] RDX: 0000000000000000 RSI: 0000000000000246 RDI: 0000000000000246
> [  200.224008] RBP: 0000000000000000 R08: ffff9fe43fde3cb8 R09: 00000000000000d5
> [  200.224008] R10: ffffbf3c8cb53d90 R11: 00000000000f4240 R12: ffff9fe43fde8700
> [  200.224008] R13: 0000000000000000 R14: ffffa0799ad6bca0 R15: ffffa0799ad6bca8
> [  200.224008] FS:  0000000000000000(0000) GS:ffff9fe43fdc0000(0000) knlGS:0000000000000000
> [  200.224008] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  200.224008] CR2: ffffffffc0b28a30 CR3: 00000097fe00a002 CR4: 00000000007606e0
> [  200.224008] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [  200.224008] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [  200.224008] PKRU: 55555554
> [  200.224008] Call Trace:
> [  200.224008]  ? process_one_work+0x195/0x390
> [  200.224008]  ? worker_thread+0x30/0x390
> [  200.224008]  ? process_one_work+0x390/0x390
> [  200.224008]  ? kthread+0x10d/0x130
> [  200.224008]  ? kthread_flush_work_fn+0x10/0x10
> [  200.224008]  ? ret_from_fork+0x35/0x40
> [  200.224008] kernel fault(0x1) notification starting on CPU 63
> [  200.224008] kernel fault(0x1) notification finished on CPU 63
> [  200.224008] CR2: ffffffffc0b28a5a
> [  200.224008] ---[ end trace c82a412d93f57412 ]---
> 
> The reason is as follows:
> T1: rmmod ipmi_si.
>     ->ipmi_unregister_smi()
>     	-> ipmi_bmc_unregister()
> 	    -> __ipmi_bmc_unregister()
> 		-> kref_put(&bmc->usecount, cleanup_bmc_device);
> 		    -> schedule_work(&bmc->remove_work);
> 
> T2: rmmod ipmi_msghandler.
> 	ipmi_msghander module uninstalled, and the module space will be freed.
> 
> T3: bmc->remove_work doing cleanup the bmc resource.
>     -> cleanup_bmc_work()
> 	-> platform_device_unregister(&bmc->pdev);
> 	    -> platform_device_del(pdev);
> 		-> device_del(&pdev->dev);
> 		    -> kobject_uevent(&dev->kobj, KOBJ_REMOVE);
> 			-> kobject_uevent_env()
> 			    -> dev_uevent()
> 				-> if (dev->type && dev->type->name)
> 		
>    'dev->type'(bmc_device_type) pointer space has freed when uninstall
>     ipmi_msghander module, 'dev->type->name' cause the sysytem crash.
> 		
> drivers/char/ipmi/ipmi_msghandler.c:
> 2820 static const struct device_type bmc_device_type = {
> 2821         .groups         = bmc_dev_attr_groups,
> 2822 };
> 
> Steps to reproduce:
> Add a time delay in cleanup_bmc_work() function, 
> and uninstall ipmi_si and ipmi_msghandler module.
> 
> 2910 static void cleanup_bmc_work(struct work_struct *work)
> 2911 {
> 2912         struct bmc_device *bmc = container_of(work, struct bmc_device,
> 2913                                               remove_work);
> 2914         int id = bmc->pdev.id; /* Unregister overwrites id */
> 2915 
> 2916         msleep(3000);   <--- 
> 2917         platform_device_unregister(&bmc->pdev);
> 2918         ida_simple_remove(&ipmi_bmc_ida, id);
> 2919 }
> 
> Fixes: b2cfd8ab4add ("ipmi: Rework device id and guid handling to catch changing BMCs")
> Signed-off-by: Wu Bo <wubo40@huawei.com>
> ---
>  drivers/char/ipmi/ipmi_msghandler.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
> index c837d54..4af3543 100644
> --- a/drivers/char/ipmi/ipmi_msghandler.c
> +++ b/drivers/char/ipmi/ipmi_msghandler.c
> @@ -3008,6 +3008,7 @@ static struct bmc_device *ipmi_find_bmc_prod_dev_id(
>  static void
>  release_bmc_device(struct device *dev)
>  {
> +	module_put(THIS_MODULE);
>  	kfree(to_bmc_device(dev));
>  }
>  
> @@ -3195,7 +3196,7 @@ static int __ipmi_bmc_register(struct ipmi_smi *intf,
>  	}
>  
>  	intf->bmc_registered = true;
> -
> +	__module_get(THIS_MODULE);
>  out:
>  	mutex_unlock(&ipmidriver_mutex);
>  	mutex_lock(&intf->bmc_reg_mutex);
> -- 
> 2.33.1
>