CVE-2025-68366

About vulnerability

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); }

Affected product:

AlmaLinux 9.2 ESU , CentOS 8.4 ELS , CentOS 8.5 ELS , CentOS Stream 8 ELS , TuxCare 9.6 ESU , Ubuntu 20.04 ELS

Affected packages:

kernel @ 5.14.0 (+5 more)

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); }