CVE-2022-49295

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-)

Moderate severity is assigned to this flaw because triggering it requires local user privileges and precise timing to race a netlink command against module unloading, restricting the blast radius to a denial of service. The Network Block Device driver is not loaded by default in standard Red Hat Enterprise Linux installations and is typically active only when explicitly configured. In addition, successful exploitation leads to a kernel crash via a null pointer dereference rather than enabling code execution or data leakage.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.