CVE-2025-68366

In the Linux kernel, the following vulnerability has been resolved:

nbd: defer config unlock in nbd_genl_connect

There is one use-after-free warning when running NBD_CMD_CONNECT and

NBD_CLEAR_SOCK:

nbd_genl_connect

nbd_alloc_and_init_config // config_refs=1

nbd_start_device // config_refs=2

set NBD_RT_HAS_CONFIG_REF open nbd // config_refs=3

recv_work done // config_refs=2

NBD_CLEAR_SOCK // config_refs=1

close nbd // config_refs=0

refcount_inc -> uaf

------------[ cut here ]------------

refcount_t: addition on 0; use-after-free.

WARNING: CPU: 24 PID: 1014 at lib/refcount.c:25 refcount_warn_saturate+0x12e/0x290

nbd_genl_connect+0x16d0/0x1ab0

genl_family_rcv_msg_doit+0x1f3/0x310

genl_rcv_msg+0x44a/0x790

The issue can be easily reproduced by adding a small delay before

refcount_inc(&nbd->config_refs) in nbd_genl_connect():

mutex_unlock(&nbd->config_lock);

if (!ret) {

set_bit(NBD_RT_HAS_CONFIG_REF, &config->runtime_flags);

+ printk("before sleep\n");

+ mdelay(5 * 1000);

+ printk("after sleep\n");

refcount_inc(&nbd->config_refs);

nbd_connect_reply(info, nbd->index);

}