CVE-2025-21701 net: avoid race between device unregistration and ethnl ops
A race condition in the Linux kernel network subsystem can cause a system crash when modifying network device channels during unregistration.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-21701?
CVE-2025-21701 is a high-severity vulnerability in Linux kernel, published on 13 Feb 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
net: avoid race between device unregistration and ethnl ops
The following trace can be seen if a device is being unregistered while its number of channels are being modified.
DEBUG_LOCKS_WARN_ON(lock->magic != lock) WARNING: CPU: 3 PID: 3754 at kernel/locking/mutex.c:564 __mutex_lock+0xc8a/0x1120 CPU: 3 UID: 0 PID: 3754 Comm: ethtool Not tainted 6.13.0-rc6+ #771 RIP: 0010:__mutex_lock+0xc8a/0x1120 Call Trace: <TASK> ethtool_check_max_channel+0x1ea/0x880 ethnl_set_channels+0x3c3/0xb10 ethnl_default_set_doit+0x306/0x650 genl_family_rcv_msg_doit+0x1e3/0x2c0 genl_rcv_msg+0x432/0x6f0 netlink_rcv_skb+0x13d/0x3b0 genl_rcv+0x28/0x40 netlink_unicast+0x42e/0x720 netlink_sendmsg+0x765/0xc20 __sys_sendto+0x3ac/0x420 __x64_sys_sendto+0xe0/0x1c0 do_syscall_64+0x95/0x180 entry_SYSCALL_64_after_hwframe+0x76/0x7e
This is because unregister_netdevice_many_notify might run before the rtnl lock section of ethnl operations, eg. set_channels in the above example. In this example the rss lock would be destroyed by the device unregistration path before being used again, but in general running ethnl operations while dismantle has started is not a good idea.
Fix this by denying any operation on devices being unregistered. A check was already there in ethnl_ops_begin, but not wide enough.
Note that the same issue cannot be seen on the ioctl version (__dev_ethtool) because the device reference is retrieved from within the rtnl lock section there. Once dismantle started, the net device is unlisted and no reference will be found.
Weakness: CWE-362
Which versions are affected by CVE-2025-21701?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-21701?
Apply the vendor's patch.
Is CVE-2025-21701 being exploited?
There is no known exploitation of CVE-2025-21701 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as A-392852041, ASB-A-392852041, BELL-CVE-2025-21701, DEBIAN-CVE-2025-21701, GHSA-268v-p5rc-rhmv, ROOT-OS-DEBIAN-11-CVE-2025-21701 and 1 more.