CVE-2025-21943 gpio: aggregator: protect driver attr handlers against module unload
A race condition in the Linux kernel GPIO aggregator driver allows local attackers to cause system instability or crashes by triggering module unload during device registration.
- 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-2025-21943?
CVE-2025-21943 is a medium-severity vulnerability in Linux kernel, published on 1 Apr 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:
gpio: aggregator: protect driver attr handlers against module unload
Both new_device_store and delete_device_store touch module global resources (e.g. gpio_aggregator_lock). To prevent race conditions with module unload, a reference needs to be held.
Add try_module_get() in these handlers.
For new_device_store, this eliminates what appears to be the most dangerous scenario: if an id is allocated from gpio_aggregator_idr but platform_device_register has not yet been called or completed, a concurrent module unload could fail to unregister/delete the device, leaving behind a dangling platform device/GPIO forwarder. This can result in various issues. The following simple reproducer demonstrates these problems:
#!/bin/bash while :; do # note: whether 'gpiochip0 0' exists or not does not matter. echo 'gpiochip0 0' > /sys/bus/platform/drivers/gpio-aggregator/new_device done & while :; do modprobe gpio-aggregator modprobe -r gpio-aggregator done & wait
Starting with the following warning, several kinds of warnings will appear and the system may become unstable:
------------[ cut here ]------------ list_del corruption, ffff888103e2e980->next is LIST_POISON1 (dead000000000100) WARNING: CPU: 1 PID: 1327 at lib/list_debug.c:56 __list_del_entry_valid_or_report+0xa3/0x120 [...] RIP: 0010:__list_del_entry_valid_or_report+0xa3/0x120 [...] Call Trace: <TASK> ? __list_del_entry_valid_or_report+0xa3/0x120 ? __warn.cold+0x93/0xf2 ? __list_del_entry_valid_or_report+0xa3/0x120 ? report_bug+0xe6/0x170 ? __irq_work_queue_local+0x39/0xe0 ? handle_bug+0x58/0x90 ? exc_invalid_op+0x13/0x60 ? asm_exc_invalid_op+0x16/0x20 ? __list_del_entry_valid_or_report+0xa3/0x120 gpiod_remove_lookup_table+0x22/0x60 new_device_store+0x315/0x350 [gpio_aggregator] kernfs_fop_write_iter+0x137/0x1f0 vfs_write+0x262/0x430 ksys_write+0x60/0xd0 do_syscall_64+0x6c/0x180 entry_SYSCALL_64_after_hwframe+0x76/0x7e [...] </TASK> ---[ end trace 0000000000000000 ]---
Weakness: CWE-362
Which versions are affected by CVE-2025-21943?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-21943?
Apply the vendor's patch.
Is CVE-2025-21943 being exploited?
There is no known exploitation of CVE-2025-21943 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-59748, AZL-59912, BELL-CVE-2025-21943, DEBIAN-CVE-2025-21943, GHSA-m7pp-g2rm-wrcq, UBUNTU-CVE-2025-21943.