Overview
About vulnerability
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:
Details
- Affected product:
- AlmaLinux 9.2 ESU , TuxCare 9.6 ESU
- Affected packages:
- kernel @ 5.14.0 (+1 more)
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: