Advisory Published
Updated

CVE-2025-21701: net: avoid race between device unregistration and ethnl ops

First published: Thu Feb 13 2025(Updated: )

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.

Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Affected SoftwareAffected VersionHow to fix
Linux Kernel
debian/linux<=5.10.223-1<=5.10.234-1
6.1.129-1
6.1.133-1
6.12.22-1
debian/linux-6.1
6.1.129-1~deb11u1

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Frequently Asked Questions

  • What is the severity of CVE-2025-21701?

    CVE-2025-21701 is classified as a moderate severity vulnerability affecting the Linux kernel.

  • How do I fix CVE-2025-21701?

    Fix CVE-2025-21701 by updating the Linux kernel to the latest stable version where the vulnerability has been addressed.

  • What systems are affected by CVE-2025-21701?

    CVE-2025-21701 affects systems running susceptible versions of the Linux kernel, particularly when handling device unregistration.

  • What potential impact does CVE-2025-21701 have?

    CVE-2025-21701 could lead to race conditions, which may affect device registration and stability of the system.

  • Is CVE-2025-21701 being actively exploited?

    As of now, there is no public knowledge that CVE-2025-21701 is being actively exploited in the wild.

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