Re: [PATCH v2] ipmi: Fix UAF when uninstall ipmi_si and ipmi_msghandler module

Corey Minyard
2021-12-21T14:05:49Z

On Tue, Dec 21, 2021 at 03:00:34PM +0800, Wu Bo wrote:
> Hi,
>
> When testing install and uninstall of ipmi_si.ko and ipmi_msghandler.ko,
> the system crashed.

Thanks for the fix, it's in my queue. I'll try to get it up soon.

-corey

>
> 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 system 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 }
>
> Use 'remove_work_wq' instead of 'system_wq' to solve this issues.
>
> 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 | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
> index c837d54..d96184d 100644
> --- a/drivers/char/ipmi/ipmi_msghandler.c
> +++ b/drivers/char/ipmi/ipmi_msghandler.c
> @@ -3031,7 +3031,7 @@ static void cleanup_bmc_work(struct work_struct *work)
> * with removing the device attributes while reading a device
> * attribute.
> */
> - schedule_work(&bmc->remove_work);
> + queue_work(remove_work_wq, &bmc->remove_work);
> }
>
> /*
> --
> 1.8.3.1
>