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CVE-2025-21701

Description

In the Linux kernel, the following vulnerability has been resolved:net: avoid race between device unregistration and ethnl opsThe following trace can be seen if a device is being unregistered whileits 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: 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+0x76/0x7eThis is because unregister_netdevice_many_notify might run before thertnl lock section of ethnl operations, eg. set_channels in the aboveexample. In this example the rss lock would be destroyed by the deviceunregistration path before being used again, but in general runningethnl operations while dismantle has started is not a good idea.Fix this by denying any operation on devices being unregistered. A checkwas 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 withinthe rtnl lock section there. Once dismantle started, the net device isunlisted and no reference will be found.

POC

Reference

No PoCs from references.

Github

- https://github.com/fkie-cad/nvd-json-data-feeds

- https://github.com/w4zu/Debian_security