Linux Kernel up to 6.17.7 netpoll refill_skbs allocation of resources

Summaryinfo

A vulnerability marked as critical has been reported in Linux Kernel up to 6.17.7. This issue affects the function refill_skbs of the component netpoll. The manipulation leads to allocation of resources. This vulnerability is referenced as CVE-2025-68169. No exploit is available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.17.7. It has been rated as critical. This issue affects the function refill_skbs of the component netpoll. The manipulation with an unknown input leads to a allocation of resources vulnerability. Using CWE to declare the problem leads to CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. Impacted is availability. The summary by CVE is:

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: 1. refill_skbs() acquires skb_pool->lock (spinlock) 2. alloc_skb() is called while holding the lock 3. Memory allocator fails and calls slab_out_of_memory() 4. This triggers printk() for the OOM warning 5. The console output path calls netpoll_send_udp() 6. netpoll_send_udp() attempts to acquire the same skb_pool->lock 7. 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.

The advisory is shared at git.kernel.org. The identification of this vulnerability is CVE-2025-68169 since 12/16/2025. The exploitation is known to be difficult. Technical details are known, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 279006 (Linux Distros Unpatched Vulnerability : CVE-2025-68169), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.17.8 eliminates this vulnerability. Applying the patch 06742a3ab884d7428c9050b205ffcf6a8a548397/327c20c21d80e0d87834b392d83ae73c955ad8ff is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (279006) and CERT Bund (WID-SEC-2025-2868). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Affected

• Debian Linux
• Amazon Linux 2
• Red Hat Enterprise Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• SUSE openSUSE
• RESF Rocky Linux
• Open Source Linux Kernel

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.17.0
• 6.17.1
• 6.17.2
• 6.17.3
• 6.17.4
• 6.17.5
• 6.17.6
• 6.17.7

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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