CVE-2023-53685: 
Linux Kernel vulnerability analysis and mitigation

A memory leak vulnerability was discovered in the Linux kernel's TUN device implementation, identified as CVE-2023-53685. The issue specifically affects the handling of detached NAPI queues in the TUN device driver (NVD).

The vulnerability occurs when NAPI and multi-queue features are enabled on a TUN device, allowing an SKB (socket buffer) to be queued into tfile->sk.skwritequeue after the queue is detached. The issue stems from a race condition between write() and ioctl(IFFDETACHQUEUE) operations that can run concurrently. The vulnerability can be triggered through a specific sequence of operations involving opening a TUN device, setting flags, and writing data (NVD).

The vulnerability results in memory leaks of socket (sk) and socket buffer (skb) structures related to the TUN device. This can lead to resource exhaustion and potential system instability over time (NVD).

The issue has been fixed in the Linux kernel by implementing a check for tfile->detached before queuing the SKB, performed under the tfile->sk.skwritequeue.lock to prevent race conditions. The fix has been incorporated into various Linux distributions, including Ubuntu and Debian (Ubuntu Security, Debian Security).