nbd: call genl_unregister_family() first in nbd_cleanup()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: nbd: call genl_unregister_family() first in nbd_cleanup() Otherwise there may be race between module removal and the handling of netlink command, which can lead to the oops as shown below: BUG: kernel NULL pointer dereference, address: 0000000000000098 Oops: 0002 [#1] SMP PTI CPU: 1 PID: 31299 Comm: nbd-client Tainted: G E 5.14.0-rc4 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) RIP: 0010:down_write+0x1a/0x50 Call Trace: start_creating+0x89/0x130 debugfs_create_dir+0x1b/0x130 nbd_start_device+0x13d/0x390 [nbd] nbd_genl_connect+0x42f/0x748 [nbd] genl_family_rcv_msg_doit.isra.0+0xec/0x150 genl_rcv_msg+0xe5/0x1e0 netlink_rcv_skb+0x55/0x100 genl_rcv+0x29/0x40 netlink_unicast+0x1a8/0x250 netlink_sendmsg+0x21b/0x430 ____sys_sendmsg+0x2a4/0x2d0 ___sys_sendmsg+0x81/0xc0 __sys_sendmsg+0x62/0xb0 __x64_sys_sendmsg+0x1f/0x30 do_syscall_64+0x3b/0xc0 entry_SYSCALL_64_after_hwframe+0x44/0xae Modules linked in: nbd(E-)

References

• https://git.kernel.org/stable/c/8a1435c862ea09b06be7acda325128dc08458e25
• https://git.kernel.org/stable/c/013a79f1b5c89290e2e97f1ebf14b14e0cf5fe5c
• https://git.kernel.org/stable/c/1be608e1ee1f222464b2856bda9b85ab5184a33e
• https://git.kernel.org/stable/c/c0868f6e728c3c28bef0e8bee89d2daf86a8bbca
• https://git.kernel.org/stable/c/cbeafa7a79d08ecdb55f8f1d41a11323d0f709db
• https://git.kernel.org/stable/c/6f505bbb8063fd3a238a4239d2d8c165e5279f6f
• https://git.kernel.org/stable/c/3d5da1ffba3388c2ae2e6c598855a4d887d3bf79
• https://git.kernel.org/stable/c/06c4da89c24e7023ea448cadf8e9daf06a0aae6e