CVE-2025-40249

In the Linux kernel, the following vulnerability has been resolved:

gpio: cdev: make sure the cdev fd is still active before emitting events

With the final call to fput() on a file descriptor, the release action

may be deferred and scheduled on a work queue. The reference count of

that descriptor is still zero and it must not be used. It's possible

that a GPIO change, we want to notify the user-space about, happens

AFTER the reference count on the file descriptor associated with the

character device went down to zero but BEFORE the .release() callback

was called from the workqueue and so BEFORE we unregistered from the

notifier.

Using the regular get_file() routine in this situation triggers the

following warning:

struct file::f_count incremented from zero; use-after-free condition present!

So use the get_file_active() variant that will return NULL on file

descriptors that have been or are being released.