CVE-2021-47100: In the Linux kernel, the following vulnerability has been resolved:  ipmi: Fix UAF when uninstall ipmi_si and ipmi_msghandler module  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_msghandl ---truncated---