[PATCH 5.4 11/47] ipmi: Fix UAF when uninstall ipmi_si and ipmi_msghandler module

Greg Kroah-Hartman
2021-12-27T15:37:58Z

From: Wu Bo <wubo40@huawei.com>

[ Upstream commit ffb76a86f8096a8206be03b14adda6092e18e275 ]

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 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>
Message-Id: <1640070034-56671-1-git-send-email-wubo40@huawei.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 8a93d5a494fff..435e9459a859f 100644
--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -2938,7 +2938,7 @@ cleanup_bmc_device(struct kref *ref)
* with removing the device attributes while reading a device
* attribute.
*/
- schedule_work(&bmc->remove_work);
+ queue_work(remove_work_wq, &bmc->remove_work);
}

/*
--
2.34.1