Deadlock Affecting perf package, versions *
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Test your applications- Snyk IDSNYK-CENTOS6-PERF-14486951
- published18 Dec 2025
- disclosed16 Dec 2025
Introduced: 16 Dec 2025
CVE-2025-68169 (opens in a new tab)How to fix?
There is no fixed version for Centos:6 perf.
NVD Description
Note: Versions mentioned in the description apply only to the upstream perf package and not the perf package as distributed by Centos.
See How to fix? for Centos:6 relevant fixed versions and status.
In the Linux kernel, the following vulnerability has been resolved:
netpoll: Fix deadlock in memory allocation under spinlock
Fix a AA deadlock in refill_skbs() where memory allocation while holding skb_pool->lock can trigger a recursive lock acquisition attempt.
The deadlock scenario occurs when the system is under severe memory pressure:
- refill_skbs() acquires skb_pool->lock (spinlock)
- alloc_skb() is called while holding the lock
- Memory allocator fails and calls slab_out_of_memory()
- This triggers printk() for the OOM warning
- The console output path calls netpoll_send_udp()
- netpoll_send_udp() attempts to acquire the same skb_pool->lock
- Deadlock: the lock is already held by the same CPU
Call stack: refill_skbs() spin_lock_irqsave(&skb_pool->lock) <- lock acquired __alloc_skb() kmem_cache_alloc_node_noprof() slab_out_of_memory() printk() console_flush_all() netpoll_send_udp() skb_dequeue() spin_lock_irqsave(&skb_pool->lock) <- deadlock attempt
This bug was exposed by commit 248f6571fd4c51 ("netpoll: Optimize skb refilling on critical path") which removed refill_skbs() from the critical path (where nested printk was being deferred), letting nested printk being called from inside refill_skbs()
Refactor refill_skbs() to never allocate memory while holding the spinlock.
Another possible solution to fix this problem is protecting the refill_skbs() from nested printks, basically calling printk_deferred_{enter,exit}() in refill_skbs(), then, any nested pr_warn() would be deferred.
I prefer this approach, given I think it might be a good idea to move the alloc_skb() from GFP_ATOMIC to GFP_KERNEL in the future, so, having the alloc_skb() outside of the lock will be necessary step.
There is a possible TOCTOU issue when checking for the pool length, and queueing the new allocated skb, but, this is not an issue, given that an extra SKB in the pool is harmless and it will be eventually used.