On Fri, Jan 16, 2026 at 9:11 AM Tzung-Bi Shih [off-list ref] wrote:

This series transitions the UAF prevention logic within the GPIO core
(gpiolib) to use the 'revocable' mechanism.

The existing code aims to prevent UAF issues when the underlying GPIO
chip is removed.  This series replaces that custom logic with the
generic 'revocable' API, which is designed to handle such lifecycle
dependencies.  There should be no change in behavior.

This series depends on the 'revocable' API, introduced in [1].  Some
build bots may report errors due to undefined symbols related to
'revocable' until the dependency is merged.

Hi Tzung-Bi!

Thank you for doing this and considering my suggestions from LPC. I
haven't looked at the code yet but I quickly tested the series with my
regular test-suites. The good news is: nothing is broken, every test
works fine. The bad news is: there seems to be a significant impact on
performance. With the user-space test-suite from libgpiod (for core C
library - gpiod-test) I'm seeing a consistent 40% impact on
performance. That's not really acceptable. :( I will try to bisect the
series later and see which part exactly breaks it.

I can also help you with user-space testing with libgpiod, if you need
it? Some documentation is available here:
https://libgpiod.readthedocs.io/en/latest/testing.html

[1] https://lore.kernel.org/chrome-platform/20260116080235.350305-1-tzungbi@kernel.org (local)

Tzung-Bi Shih (23):
  gpiolib: Correct wrong kfree() usage for `kobj->name`
  gpiolib: cdev: Fix resource leaks on errors in gpiolib_cdev_register()
  gpiolib: Fix resource leaks on errors in gpiochip_add_data_with_key()
  gpiolib: Fix resource leaks on errors in lineinfo_changed_notify()
  gpiolib: cdev: Correct return code on memory allocation failure

=> The first 5 patches are fixes.  They aren't directly related to the
   replacement, and should be able to apply independently.

Awesome, I'll make them a priority.

  gpiolib: Access `gpio_bus_type` in gpiochip_setup_dev()
  gpiolib: Remove redundant check for struct gpio_chip
  gpiolib: sysfs: Remove redundant check for struct gpio_chip
  gpiolib: Ensure struct gpio_chip for gpiochip_setup_dev()
  gpiolib: cdev: Don't check struct gpio_chip in gpio_chrdev_open()

=> The following 5 patches are refactors.  Makes the subsequent changes
   easier or at least clear.

  selftests: gpio: Add gpio-cdev-uaf tests

=> The following patch adds kselftest cases for some classic UAF
   scenarios.

Thanks, these too look like v7.0 material for me. I'll try to review
these ASAP too.

Bart