CVE-2023-52609: 
Linux Debian vulnerability analysis and mitigation

CVE-2023-52609 is a vulnerability in the Linux kernel's binder driver that was discovered and patched in December 2023. The vulnerability involves a race condition between mmput() and do_exit() operations in the binder driver, affecting the memory management subsystem (Kernel Git).

The vulnerability occurs when Task A calls binderupdatepagerange() to allocate and insert pages on a remote address space from Task B. Task A pins the remote mm via mmgetnotzero() first, which can race with Task B's doexit() call. In this scenario, the final mmput() refcount decrement comes from Task A. The work of __fput() from Task B is queued up in Task A as TWA_RESUME, but Task A may sleep waiting for a reply from the terminated Task B (Kernel Git).

The vulnerability results in blocked binderdeferredrelease() operations and delayed death notifications until an unrelated binder event forces Task A to return to userspace. This can lead to resource leaks and potential system performance degradation (Kernel Git).

The issue has been fixed by replacing mmput() with mmputasync() which schedules the work in the corresponding mm->asyncput_work WQ instead of Task A. The fix has been incorporated into various Linux kernel versions and distributions including Ubuntu and Debian (Ubuntu Security, Debian LTS).