Memory Leak in Linux Kernel Network Scheduler

Executive Summary

This vulnerability exists in the Linux kernel's network scheduler (net_sched) where there is a memory leak related to skb (socket buffer) objects during deferred queueing discipline (qdisc) drops.

Specifically, when the network stack cleans up the deferred list using the function qdisc_run_end(), it operates on the root qdisc. If the root qdisc does not implement the TCQ_F_DEQUEUE_DROPS flag, packets that should be freed remain stranded on the child's local to_free list and are never actually freed, causing a memory leak.

The fix involves making the function qdisc_dequeue_drop() aware of the root qdisc by checking for the TCQ_F_DEQUEUE_DROPS flag. If the flag is present, packets are appended directly to the root's to_free list; otherwise, packets are dropped directly as before the optimization.

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Impact Analysis

This vulnerability can lead to a memory leak in the Linux kernel's network stack, which means that memory allocated for network packets may not be properly freed.

Over time, this could cause increased memory usage, potentially degrading system performance or leading to resource exhaustion, which might result in network instability or crashes.

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Mitigation Strategies

The vulnerability has been resolved in the Linux kernel by fixing the skb memory leak in deferred qdisc drops. To mitigate this vulnerability, you should update your Linux kernel to a version that includes this fix.

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